STRUCTURE magazine | March 2013

A Joint Publication of NCSEA | CASE | SEI

STRUCTURE

®

March 2013 Seismic NCSEA Winter Leadership Forum Tucson, Arizona March 7 & 8

SPECIFICATION

“BEST

PRACTICE”

Ensure That Your Project Documents Match Your Design SCAN THIS QR CODE TO LINK TO A DIGITAL SPECIFICATION FOR ANCHORS WRITTEN AND PROVIDED BY POWERS FASTENERS WITH GOVERNING STANDARDS REFERENCED.

Today in virtually every jurisdiction in the U.S. the “Code Basis for Building Construction” is in some edition of the International Building Code (IBC). By default, the General Notes, Structural and MEP Specifications require compliance to the IBC. For the purpose of post-installed concrete anchor design, the IBC requires that the “Strength Design” method be used.

The reality is far too often these specifications are obsolete with respect to anchors in concrete.

When that happens, the project documents are in conflict with one another and in conflict with the IBC.

CSI Section for Mechanical & Adhesive Anchors – 03 16 00 and 05 05 19 Don’t put your project at risk. Powers understands the importance of code approved anchoring options. That’s why we’ve dedicated ourselves to engineering a range of products that meet the new building code, and to developing ways to support those products.

Real-Time Anchor Design Software V2.0

PDA’S LIVE UPDATE FEATURE ENSURES THAT SOFTWARE IS ALWAYS LOADED WITH UP-TO-DATE PRODUCTS, FEATURES AND CODE REFERENCES.

For a full listing of code approved products, and a demo on the latest version of PDA go to www.powers.com or call (800) 524-3244 for a free demo.

Powers Fasteners, Inc. www.powers.com 2 Powers Lane P: (914) 235-6300 Brewster, NY 10509 F: (914) 576-6483

Still creating multiple steelwork models?

Choose Fastrak for your steel building design and synchronize your models seamlessly with BIM platforms like Autodesk® Revit®.

Design composite floors and complex steelwork within a single Fastrak model

See Fastrak for yourself Visit us online and request a demo at cscworld.com/DiscoverFastrak

Perform gravity and lateral design within a single Fastrak model Start modeling in either Fastrak or Revit® Save valuable design and drafting time by only building one model Make amendments in Fastrak and Revit® simultaneously Synchronize models at any time during the design process

Structural Industry Partners

Use audit features to show what’s been changed during synchronization

Thousands of engineers choose CSC software “We looked at many different design packages but Fastrak was the best choice when using BIM tools like Autodesk® Revit®.

Now, we can build a model in Revit®, synchronize it as many times as necessary and save ourselves lots of time.”

Michael A. Tracey, P.E., Senior Structural Engineer, Bergmann Associates®

Evolutionary software. Revolutionary service.

877 710 2053 (Toll Free) www.cscworld.com

Delivering:

#cscworldglobal

CONTENTS

FEATURES Crossed Arches Pipe Bridge

38

March 2013

By Wayne A. Bamossy, P.E., Jennifer A. Barrick, P.E. and William W. Lai, P.E.

DEPARTMENTS

Overall simplicity and sparing use of material contribute to what strikes many as the elegant appearance of the pipe bridge recently built across the Tujunga Channel in the Lake View Terrace area of Los Angeles. The bridge is part of the Hansen Dam Golf Course Water Recycling Project, joining several other golf courses, cemeteries, parks, and nurseries that use recycled water for irrigation of large areas of turf or other landscaping.

54 Code Updates AISI 202-11

By Jeffrey M. Klaiman, P.E.

57 Legal Perspectives Scope of Services 101

By Alfred Zarlengo

59 Business Practices

Modeling and Analysis of a Masonry Building on Piling

42

How Long Do I Need To Keep My Records?

G. Daniel Bradshaw

By Louis Scatena, P.E.

61 Great Achievements

The Generator Building will enclose large electrical equipment at a water treatment facility that is near a major seismic fault in northern California. The project included seismic design considerations that, taken collectively, made modeling the otherwise unimposing Generator Building somewhat unusual. This article summarizes the development of the structural model.

Frank Osborn

By Richard G. Weingardt, P.E.

74 Structural Forum Engineers and the Public Good

By Ashvin A. Shah, P.E.

COLUMNS 9 Editorial Showcasing the Future of the Profession

By Joshua Gionfriddo, E.I.T.

The Internal Goods of Engineering

16 Practical Solutions Seismic Time Histories

By Kyle D. Harris, P.E, Nicholas D. Robinson, P.E. and Eric L. Sammarco, P.E.

20 Codes and Standards The International Green Construction Code

By Christine A. Subasic, P.E.

25 Structural Practices The RFP for the Geotechnical Report

By Gerd W. Hartung, P.E., S.E. and Richard O. Anderson, P.E.

By Dallin Pedersen, P.E., Emily Guglielmo, P.E., C.E. and Timothy M. Gilbert, P.E., S.E.

70 SEI Structural Columns 72 CASE in Point

Evaluating Existing Masonry Construction

By Andrew Geister, P.E.

44 Structural Design Wood-framed Stair Stringer Design and Construction

By Christopher R. Fournier, P.E.

48 Just the FAQs Arc Spot Welding Steel Deck – A Primer

By Thomas Sputo, Ph.D., P.E., S.E., SECB

51 InSights Power Forward

By William Gould, P.E. and Drew Liechti, P.E.

STRUCTURE magazine

5

March 2013

®

34 Structural Testing

ON

THE

COVER

In-plane shear cracks from the February 2011 Christchurch New Zealand earthquake. This month’s issue will look into the need to revisit codes to minimize earthquake damage. Photo courtesy of David Biggs.

A Joint Publication of NCSEA | CASE | SEI

By Sissy Nikolaou, Ph.D., P.E.

64 Resource Guide (Software Updates) 68 NCSEA News

Three Perspectives on Encouraging Younger Engineers

STRUCTURE

The Eastern United States

7 Letter to the Editor

31 Professional Issues

11 InFocus

12 Structural Performance

7 Advertiser Index

Bringing It All In-House

By Taka Kimura, P.E.

By Jon A. Schmidt, P.E., SECB

IN EVERY ISSUE

28 Technology

March 2013 Seismic NCSEA Winter Leadership Forum Tucson, Arizona March 7 & 8

Publication of any article, image, or advertisement in STRUCTURE® magazine does not constitute endorsement by NCSEA, CASE, SEI, C 3 Ink, or the Editorial Board. Authors, contributors, and advertisers retain sole responsibility for the content of their submissions.

What should I consider when using HSS for seismic bracing?

You should check out this video — helped me a lot: HSS Flexes Its Muscles

As a fabricator, what specific challenges do you encounter when working with HSS? Good question. View this forum thread: HSS Challenges

Does anyone have software recommendations for designing HSS connections?

Atlas recently addressed this in a thread.

Go here: HSS Connections

Get answers with

Introducing Atlas Connection.

When it comes to heavy industry and manufacturing, you can’t let questions jeopardize your deadline, quality or safety. That’s why we created Atlas Connection, a free online forum that connects structural engineers to the answers they need — when they need them.

When every connection counts, connect with Atlas Tube.

Join today — atlasconnection.com

Advertiser index American Concrete Institute .........................10 Canadian Wood Council ...............................67 Cast ConneX.................................................47 Computers & Structures, Inc. .......................76 CoreBrace, LLC ............................................33 CSC, Inc. ........................................................3 CTP, Inc........................................................62 CTS Cement Manufacturing Corp................19 ENERCALC, Inc. ...........................................8 Engineering International, Inc.......................14 Foundation Performance Association.............32 Fyfe ...............................................................55

PleAse suPPort these Advertisers GT STRUDL................................................30 Halfen, Inc. ...................................................24 Hayward Baker, Inc. ........................................4 Hilti, Inc. ......................................................50 Integrated Engineering Software, Inc.............40 ITW Red Head .............................................53 ITW TrusSteel & BCG Hardware ...........27, 37 JMC Steel Group ............................................6 JQ .................................................................52 KPFF Consulting Engineers ..........................46 Microdesk .....................................................29 NCEES .........................................................58

editorial Board

Advertising Account MAnAger

Chair

Interactive Sales Associates Chuck Minor

Dick Railton

Eastern Sales 847-854-1666

Western Sales 951-587-2982

sales@STRUCTUREmag.org

execdir@ncsea.com

Christine M. Sloat, P.E.

publisher@STRUCTUREmag.org

Associate Editor

Web Developer

Craig E. Barnes, P.E., SECB CBI Consulting, Inc., Boston, MA

Dilip Khatri, Ph.D., S.E.

STRUCTURE® (Volume 20, Number 3). ISSN 1536-4283.

Publications Agreement No. 40675118. Owned by the National Council of Structural Engineers Associations and published in cooperation with CASE and SEI monthly by C3 Ink. The publication is distributed free of charge to members of NCSEA, CASE and SEI; the non-member subscription rate is $65/yr domestic; $35/yr student; $90/yr Canada; $125/yr foreign. For change of address or duplicate copies, contact your member organization(s). Any opinions expressed in STRUCTURE magazine are those of the author(s) and do not necessarily reflect the views of NCSEA, CASE, SEI, C3 Ink, or the STRUCTURE Editorial Board.

STRUCTURE® is a registered trademark of National Council of Structural Engineers Associations (NCSEA). Articles may not be

reproduced in whole or in part without the written permission of the publisher.

www.ncsea.com 3

C Ink, Publishers

A Division of Copper Creek Companies, Inc. 148 Vine St., Reedsburg WI 53959 P-608-524-1397 F-608-524-4432 publisher@STRUCTUREmag.org

Visit STRUCTURE magazine magazine on-line at Visit STRUCTURE online Visit STRUCTURE magazine on-line at at www.structuremag.org www.structuremag.org www.structuremag.org

Greg Schindler, P.E., S.E.

Stephen P. Schneider, Ph.D., P.E., S.E.

Brian J. Leshko, P.E.

John “Buddy” Showalter, P.E.

CCFSS, Rolla, MO

Mercer Engineering, PC, Minot, ND

William Radig

Evans Mountzouris, P.E.

The DiSalvo Ericson Group, Ridgefield, CT

Roger A. LaBoube, Ph.D., P.E.

Rob Fullmer

webmaster@STRUCTUREmag.org

Davis, CA

KPFF Consulting Engineers, Seattle, WA

HDR Engineering, Inc., Pittsburgh, PA

graphics@STRUCTUREmag.org

Brian W. Miller

Khatri International Inc., Pasadena, CA

Nikki Alger

publisher@STRUCTUREmag.org

Graphic Designer

Burns & McDonnell, Kansas City, MO chair@structuremag.org

Heath & Lineback Engineers, Inc., Marietta, GA

Executive Editor Jeanne Vogelzang, JD, CAE Editor

Jon A. Schmidt, P.E., SECB

Mark W. Holmberg, P.E.

editoriAL stAFF

Nemetschek Scia ...........................................60 Powers Fasteners, Inc. ......................................2 QuakeWrap ...................................................45 RISA Technologies ........................................75 SidePlate Systems, Inc. ..................................17 Simpson Strong-Tie.......................................23 Soilstructure.com ..........................................65 Star Seismic ...................................................35 Struware, Inc. ................................................13 Subsurface Constructors, Inc. ........................41 Taylor Devices, Inc. .......................................63 Unbonded Brace ...........................................56

John A. Mercer, P.E.

BergerABAM, Vancouver, WA

American Wood Council, Leesburg, VA

Amy Trygestad, P.E.

Chase Engineering, LLC, New Prague, MN

Letter to the Editor As a long time Structural Engineer, I read STRUCTURE magazine regularly, and appreciate the selection of articles. Upon seeing the cover of the January 2013 issue, I was compelled to share some of my experience.

I believe that a significant number of failures can be attributed to the structural design engineer for not having, or insisting on, the opportunity to inspect his/her design in the field before it is covered up or hidden from view. The person who designed the reinforcing, for example, can tell more quickly than almost anyone if it is the same size and placement as he intended.

In the old days, when engineers were a subcontract to the architect, there was no budget for the engineer’s on-site inspection. I used to go out on my own, without pay, to inspect my design. As often as 50 percent of the time, I found things that needed to be corrected which I documented in a report that went to my Partners, the Owner, the Contractor and the City Inspector.

I do not know whether these instances were ignorance or fraud, intentional or accidental In some cases, failure would

7

March 2013

have happened if it had not been discovered and corrected.

I’ve heard all types of excuses, including: • “They weren’t needed.” (50% of the plug welds on a steel deck) • “I never had to do it that way before.”

• “I’ve always done it that way.”

• “I couldn’t understand why it was necessary.”

• “We have never had to do engineered drawings before, and I don’t know how to read them.”

• “My supervisor said we could save money if we omitted every other bar (or spaced them farther apart).”

Chapter 17 of the International Building Code allows us to “invite ourselves” to the field to “Observe” our design. On the front page of my set of plans, I have a separate section entitled “Structural Observation”; here is where I list the items I wish to look at before they are covered up or hidden from view. It’s worth the trip, education, and good public relations.

Sincerely, James D. Leach, S.E. California Registered Structural Engineer

For over three decades engineers have relied on ENERCALC’s industry leading software to perform structural design and analysis for low to mid-rise buildings.

• Software for rapid creation of calculations for components of low to mid-rise buildings

ENERCALC

• Covers virtually all design & analysis tasks in steel, wood, concrete, masonry, load generation and frame analysis • Latest IBC, ACI, ASCE, AISC, NDS and CBC code provisions incorporated • Flexible licensing, automatic web updates, superb support, created by experienced engineers • Celebrating 30 years and 8,000+ users • Improved continuously to suit user’s needs

Latest News Update:

ENERCALC

Recent new additions include biaxial footings, wood design for 2D frames, wood shear walls, project load set builder, seismic demands for non-structural components, seismic wall anchorage, ASCE 7-10 wind loads and an extensive improvement to code required load combination capabilities.

800.424.2252 | www.enercalc.com | info@enercalc.com Evaluation Software: www.enercalc.com/demo

editorial

Showcasing new trends, new techniques theandFuture current industry of issues the Profession

By Taka Kimura, P.E., M. ASCE, F. SEI

E

ach year, the Structural Engineering Institute (SEI) gives undergraduate engineering students the opportunity to apply what they’ve learned, and showcase their engineering skills, through the annual SEI Student Competition. I want to take this opportunity to recognize the top three teams from last year’s competition and to tout this program’s many benefits.

The first place team from Villanova consisted of Stephen Kane, Scott Albarella, John Garland, Michael Mignella, and Louis Ross with Zeyn Uzman as their faculty advisor. Their project, “US Rte. 67 Corridor Project–Jerseyville Bypass Bridge Design”, addressed the design of a 140-foot long simple span, steel plate girder bridge with a composite concrete deck as part of a multibillion dollar roadway improvement project being implemented by the Illinois Department of Transportation. Their submission was impressive and displayed a professional level of effort. Calculations included deflection limits, constructability requirements, and a cost analysis to determine the optimum number of girders.

Second place went to the team from the University of Colorado, Denver, for their “Idaho Springs Maintenance Facility” project. Team members John Pettit, Jose Cordoba, Jeff Gee, Ramon Martinez, and Jeff Felling, under the direction of Faculty Advisor Peter Marxhausen, designed a 6,500 square foot maintenance building for the Idaho Springs Public Works Department. Interior space functionality, sustainability, site conditions, and surrounding architecture were all factors considered in this project that was presented to City officials.

The team from the Milwaukee School of Engineering captured third place with their project, “Sweet Water Organics Vertical Farm Design”.

Team members Austin Meier, Mark Peterson, and Stephanie Pichotta, with Faculty Advisor Christopher Raebel, designed a vertical farming structure for Sweet Water Organics in Milwaukee, Wisconsin. This urban farming and aquaponics facility had very specific and unusual functional and architectural requirements that posed a unique challenge for the team.

I was struck by the high caliber of the submissions, the depth to which each team analyzed their project, and the dedication of each team member and faculty advisor to go above and beyond what is typically expected in an undergraduate engineering course. These professional level projects took the participating teams beyond classroom theories and gave them real world experience. Students who had learned about stress and strain were required to consider bigger picture concerns such as client preferences, cost effectiveness, and efficient use of interior space.

Zeyn Uzman, the Villanova team’s faculty advisor, is a full time structural engineer but teaches on the side as an adjunct professor. He requires his students to approach the Student Competition with the perspective of a practicing engineer. “I tell my students that they are no longer in school, but work under my direction as they would in an engineering firm. I explain to them that there is no partial credit. A mistake in a design can cost lives.” CU Denver’s faculty advisor, Peter Marxhausen, agrees that the competition “encourages senior-level civil engineering students to look at a large-scale infrastructure project and develop a solution that is real, comprehensive, and worthy of a peer review from SEI.” Chris Raebel, faculty advisor for the Milwaukee School of Engineering team adds, “this was a great opportunity for the students to present on a bigger stage than they are used to.”

STRUCTURE magazine

The first place team from Villanova.

The second place team from the University of Colorado.

The third place team from the Milwaukee School of Engineering.

The competitors are also required to learn important soft skills.

Effective time management, teamwork, and good communication, both verbal and written, are hallmarks of successful teams. These skills translate directly into career success once the students graduate. Steve Kane from the Villanova team states, “We were able to use many of the technical skills we had learned throughout our 4 years, but also put in to practice the time management and teamwork skills we had honed through various other smaller scale projects.” Austin Meier from the Milwaukee School of Engineering team adds, “Being able to properly communicate one’s idea in a presentable and professional format is a great tool to have in one’s repertoire.”

Established in 2009, the SEI Student Competition continues to grow and attract some of the country’s best and brightest structural engineering students. It recognizes emerging talent and allows them to shine before members of their future profession at the SEI Structures Congress, where the top three teams are invited to present their projects. This competition clearly has an impact on those who participate.

“Being recognized by such an important group of people at the SEI conference is the biggest honor I had” affirms José Cordoba from the University of Colorado, Denver team.

The success of the competition is largely due to the tireless efforts of Jonathan Goode, Chair of the SEI Student Initiatives Committee. Kudos to Jonathan and his committee for their devotion to the development of the structural engineering profession!

Details of the SEI Student Competition, instructions on how to enter, and more information on last year’s winning projects can be found on the SEI website at http://content.seinstitute.org/ StudentStructuralDesignCompetition.html. If you are at the Structures 2013 Congress in Pittsburgh on May 2-4, attend the session featuring this year’s Student Competition winners for a glimpse at the future of our profession. You won’t be disappointed!▪ Taka Kimura, P.E., M. ASCE, F. SEI is a Senior Principal Engineer at Parsons Brinckerhoff. Taka currently serves as Vice President of the Structural Engineering Institute.

9

March 2013

ACI Seminars—Outstanding Content, Great Value ACI seminars are developed and presented by industry leaders from each topic area and backed by documents recognized as the go-to standards for the concrete industry. Many seminars even come with free publications worth over half the registration price. But don’t take our word for it, over 96% of attendees at 2012 seminars would recommend them to their peers!

ACI can also bring these outstanding seminars directly to your office.

To learn more about ACI seminars and to register, visit www.concreteseminars.org.

Adhesive Anchors Chicago, IL—April 4, 2013 Las Vegas, NV—April 9, 2013 Baltimore, MD—April 11, 2013 Minneapolis, MN—April 18, 2013 New Brunswick, NJ—April 23, 2013 Dallas, TX—April 30, 2013 Jacksonville, FL—May 7, 2013 Denver, CO—May 9, 2013 Portland, OR—May 14, 2013 New Orleans, LA—May 16, 2013 Kansas City, KS—May 23, 2013 Pleasanton, CA—May 30, 2013 Williamsburg, VA—June 6, 2013

Concrete Slabs-on-Ground Atlanta, GA—May 7, 2013 Pittsburgh, PA—June 4, 2013 Simplified Design Charlotte, NC—April 8, 2013 Nashville, TN—April 24, 2013 Little Rock, AR—May 1, 2013 Miami, FL—May 8, 2013 Indianapolis, IN—June 12, 2013 Troubleshooting Concrete Construction Cincinnati, OH—May 15, 2013 San Diego, CA—May 21, 2013

Concrete Repair Basics Albany, NY—May 29, 2013 Des Moines, IA—June 5, 2013

RESOURCES FOR SUCCESS FROM ACI! 248-848-3800  www.concrete.org

Coming to a Code near you!

inFocus

The new trends, Internal new techniques Goods and current ofindustry Engineering issues

By Jon A. Schmidt, P.E., SECB

I

n my last column, I proposed that the proper purpose of the practice of engineering is the material well-being of all people.

This month, I would like to elaborate a bit on what this means and explore in more detail how engineers uniquely pursue it.

Philosophers Allison Ross and Nafsika Athanassoulis addressed this subject in a 2010 paper (“The Social Nature of Engineering and Its Implications for Risk Taking”, Science and Engineering Ethics, Vol. 16, No. 1, pp. 147-168). In their words, “Engineering projects provide us with the technological means of overcoming some of the physical limitations that are a consequence of being human.” Engineering is thus “a profession that seeks to harness technological advancements to provide solutions to a wide range of social problems.” Note that material well-being, here characterized as technological advancement, is not strictly separate from physical and social well-being; instead, it facilitates both in a particular way.

Ross and Athanassoulis zero in on the aspect of engineering that I believe is crucial to understanding the peculiar ethical burden that engineers bear: Engineering projects are often innovative, long-term and involve the co-ordination of so many different variables that it is impossible to predict absolutely accurately what their consequences will be. In addition, because of the scale and infra-structural nature of these projects there is often significant potential to do harm should something go wrong.

As a result, the engineer assumes a responsibility to determine which hazards are pertinent to each undertaking, decide how best to deal with them in spite of the uncertainty surrounding them, and inform everyone who needs to become aware of them. In other words, the basic societal role of engineering is the assessment, management, and communication of risk.

Ross and Athanassoulis point out that people participate in any instance of risk-taking in three ways: as the decision-maker, as the potential harm-bearer, or as the intended beneficiary. It is not morally problematic when the same person occupies all three positions, but for engineering risks, multiple parties are always implicated – the engineer makes the decision, the public is often in harm’s way, and the engineer’s employer or client presumably stands to gain something.

This is what makes engineering an “ethically complex” profession (“The Social Captivity of Engineering,” May 2010).

Significantly, the precise identity of the potential harm-bearer is usually unknown to the engineer; a population is put “at risk,” not a designated individual or group. It may even encompass members of a future generation when something like environmental impact is at stake. Under such circumstances, what factors influence whether the risks associated with a given engineering decision are reasonable, and therefore justifiable?

Ross and Athanassoulis reject the widespread assumption that this is purely a matter of “objective” probabilistic calculation. Instead, a number of “subjective” considerations must also come into play, including the desires and priorities of the engineer, different perspectives on how to characterize various outcomes should they come about, STRUCTURE magazine

and the range of available options. Therefore, “the assignment of moral responsibility for risk-taking and for the results of risk-taking needs to be done on a case by case basis.”

This is not to say that engineering ethics is consigned to a form of relativism. On the contrary, “engineers, like other professionals, have distinctive reasons to take or refuse to take risks that they acquire by being members of their particular profession.” They share a common consensus – although they rarely articulate it – about what they do and how it fits into the bigger picture, which Ross and Athanassoulis describe as follows: It is our contention that the chief good internal to the practice of engineering is safe efficient innovation in the service of human wellbeing and that this good can only be achieved where highly accurate, rational decisions are made about how to balance the values of safety, efficiency and ambition in particular cases… engineers don’t just strive to find technological solutions to human problems, they strive to do so in a manner fitting for the conduct of an engineer which involves consciously foregrounding the values of safety and sustainability.

This passage invokes the notion of an internal good and connects it directly with engineering’s proper purpose. However, the references to “values” seem out of place, and the attempt to pinpoint a single internal good strikes me as needlessly restrictive. Instead, I advocate rearranging the terminology to recognize three such goods: • Safety – protecting people and preserving property.

• Sustainability – improving environments and conserving resources.

• Efficiency – performing functions while minimizing costs.

These three types of risk mitigation are goals inherent in nearly every engineering endeavor today. Engineers can – and regularly do, even if only subconsciously – treat them as ends in themselves, rather than as means to some other end, and successfully achieving them legitimately contributes to the material well-being of all people. They qualify as goods that are internal to the practice of engineering because they are specific to it, can only be fully understood by those who participate in it, and generally benefit the entire practicing community.

Even so, it is important to acknowledge that safety, sustainability, and efficiency may be – and in fact, frequently are – in tension with each other to some extent. Most notably, Ross and Athanassoulis observe that “decisions about risk made by engineers require them to weigh their concerns about risk against economic considerations … the demands of efficiency and safety/minimisation of risk tend to conflict.” The question then arises: What personal attributes would enable someone to make the necessary trade-offs among them without inappropriately compromising any of them? That will be the subject of my next two columns.▪

11

Jon A. Schmidt, P.E., SECB (chair@STRUCTUREmag.org, twitter.com/JonAlanSchmidt), is an associate structural engineer at Burns & McDonnell in Kansas City, Missouri. He chairs the STRUCTURE magazine Editorial Board and the SEI Engineering Philosophy Committee.

March 2013

Structural Performance performance issues relative to extreme events

Figure 1: Comparison of USGS Did you Feel It? Maps from the 2011 M5.8 Mineral, VA (green) and the 2004 M6.0 Central California (red) earthquakes. Stars show epicenters and dots show locations where people reported at least weak shaking (usgs.gov).

T

he need to address regional aspects of the Eastern United States (EUS) in model building codes became even more evident with the 2011 Mineral, Virginia earthquake, the most felt event in modern US history, considering the extraordinarily large felt geographic area combined with a high population density. This article presents some facts of the 2011 earthquake that, when coupled with evidence from analytical studies and better understanding of the local geology and tectonic setting, highlight key seismic design issues that are not addressed sufficiently in present codes.

The issues include seismic hazard mapping, site classification and procedures that dictate seismic detailing through ground motion acceleration limits and Seismic Design Categories. Current ongoing efforts to adjust the national procedures, specifically for the EUS, are discussed.

The Eastern United States We had an Earthquake in Virginia – Now what?

By Sissy Nikolaou, Ph.D., P.E.

Dr. Nikolaou, P.E. a Senior Associate at Mueser Rutledge Consulting Engineers, currently leads the firm’s GeoSeismic department. She specializes in risk- and performance-based seismic design and soil-structure interaction. Dr. Nikolaou can be reached at snikolaou@mrce.com.

Specific references noted in this article (e.g. [1], [2], etc.) can be found in the online version at the STRUCTURE magazine website, www.STRUCTUREmag.org.

The 2011 Mineral, VA Earthquake On August 23, 2011 an earthquake occurred in the state of Virginia (VA), with a magnitude of M5.8 and a maximum perceived intensity of VII on the Modified Mercalli Intensity scale. The epicenter was in Louisa County, 5 miles from the town of Mineral, 38 miles northwest of the state capital of Richmond and 84 miles southwest of Washington, DC. The shallow earthquake occurred within the top 4 miles of the earth’s crust, within the known Central VA Seismic Zone. It was the largest EUS earthquake since the M5.9 1897 Giles County, VA, event.

Details can be found in a report by the Earthquake Engineering Research Institute (EERI.org) [1]. The major effects of this earthquake, which caused no fatalities or significant injuries, can be summarized as follows:

12 March 2013

Felt Area and Wave Attenuation The main “felt area” extended more than 500 miles from the epicenter, making the 2011 VA Earthquake the most felt event in modern US history. Reports came from a maximum distance of 1,000 miles, an astonishing distance for an earthquake of this moderate magnitude, covering an area where more than one-third of the US population resides. The slow decay of this earthquake energy is a regional characteristic that can be attributed to the older, less worked, and harder regional bedrock that generates high frequency earthquake motions and that can travel great distances before they subside. To illustrate the comparison of EUS earthquakes vs. Western United States (WUS) earthquakes, Figure 1 presents the US Geological Survey (USGS) Did You Feel It? map from the VA earthquake and a similar event in magnitude (M6.0) from a California earthquake in 2004.

Ground Motion Records and Geology The attenuation of recorded Peak Ground Acceleration (PGA) values as a function of the distance from the epicenter is shown on Figure 2 from stations along the East Coast from South Carolina to Vermont. The records became available to EERI and the Geotechnical Extreme Events Reconnaissance (GEER) research teams from the Center for Engineering Strong Motion Data (CESMD) and the North Anna Nuclear Power Plant with the exact site conditions not known in detail.

The horizontal Spectral Accelerations (SA) for the records from four of the stations located within VA are shown on Figure 3 and are compared to contemporary local code-based SA for Site Classes C, D, E. Without exact station site conditions known, we cannot make firm conclusions on the directionality effects. However, it appears that stations located closer to the Fall Line (in proximity to Interstate 95) exhibited greater directionality than those located farther away, as shown in the motions

(August 2011 Virginia Earthquake)

1

CESMD Stations North Anna Nuclear Power Plant

(Mat)

0.1

0

200

400

Boston, MA

Atlanta, GA

New York, NY

0.0001

Philadelphia, PA

0.001

Charleston, SC

0.01

Washington, D.C.

Peak Ground Acceleration, PGA : g

(Deck)

600

800

Distance from the Epicenter, D : km

Figure 2: Peak Ground Acceleration (PGA) vs. distance from the Epicenter from CESMD and the North Anna Nuclear Power Plant stations.

from North Anna (NAP), Reston (RES), and Corbin (CBN) stations, which are close to the Fall line. The Fall line is a line that separates, geologically, the east coast into inboard bedrock areas and outboard cretaceous coastal areas (Figure 4 ). Some strong site amplification effects in the CBN station records may be due to site or topographic effects.

Figure 3: Acceleration response spectra from selected 2011 M5.8 Mineral, VA records. Black lines represent Site class C, D, E design response spectra from contemporary state building code based on IBC-06 (ASCE7-05).

MD WV

VA MD RES

WV

Washington

DE MD

VA

CWA

Structural Damage

NAP

CBN

Epicenter Richmond

Roanoke Predicted extend of landslides for M=5.8 (modified from Jibson and Harp, 2012)

0

VA NC

25

50mi

Norfolk 0

25

50 km

Figure 4: Map showing the Fall Line; epicenter; approximate observed limits in bold ellipse; previous max limit for same magnitude earthquake in circle around epicenter (modified from Jibson & Harp, 2012; base map from USGS National Geologic Map Database) usgs.gov.

Nuclear Reactor The North Anna Power Plant, just 11 miles from the epicenter, had to shutdown, activating backup power generation as SA and PGA values for the Operating and Design Basis Earthquakes were exceeded for Power Station Units 1 and 2 (Figure 2). The PGA at the foundations of the reactor containment reached 0.26 g with a design value of 0.12 g. No structural damage to safety components was identified, but non-critical components, such as the building’s concrete masonry unit (CMU) walls, exhibited hairline diagonal cracks, and 27 massive steel storage casks, for spent fuel rods, slid on their concrete slabs by as much as 4.5 inches. continued on next page

STRUCTURE magazine

13

March 2013

The easiest to use software for calculating wind, seismic, snow and other loadings for IBC, ASCE7, and all state codes based on these codes ($195.00).

Tilt-up Concrete Wall Panels ($95.00).

Floor Vibration for Steel Beams and Joists ($100.00).

Concrete beams with torsion ($45.00).

Demos at: www.struware.com

ADVERTISEMENT–For Advertiser Information, visit www.STRUCTUREmag.org

Widespread structural damage was observed, with the most common in unreinforced masonry walls, gable walls, and chimney breaks or collapses (Figure 5 , page 14 ). Across Virginia, 33 residences were destroyed and 180 suffered major damage. Two schools were severely damaged, with the Louisa County High School having to convert into modular units five months later. In the Washington, DC area, the Washington Monument, the Smithsonian Institution, the National Cathedral, and Congressional buildings all suffered damage in addition to other private office and residential structures [1].

Heavier damage was observed in the coastal plain areas of south Maryland and Delaware, rather than at sites within the firm inland rock region that are closer to the epicenter.

In this area of higher damage, relatively shallow soft deposits overlying the hard regional bedrock can create very large soil amplification effects that far exceed Code values that would affect mostly low-period structures [2].

Minor damages were reported as far away as in New Jersey and New York, which is more than 250 miles northeast from the epicenter, and in South Carolina, which is more than 370 miles southwest. Damage estimates were approximately $300 million overall, and on the order of $90 million in VA alone [1].

Baltimore

Figure 5: Masonry damage in Louisa County.

Non-structural components damage from Louisa County High School (GEER Photos by R. Green, EERI Clearinghouse, eeri.org).

Geotechnical Observations While no large landslides occurred, many rock/ soils falls were triggered at natural cliffs and steep road cuts with ground accelerations as low as 0.02 g to 0.04 g. In a comprehensive study published in December 2012 [3], the authors, Jibson & Harp, mapped the occurrence of rock falls. The distance limits for these occurrences reached 150 miles from the epicenter, exceeding by a factor of 4 observations from historic earthquakes with magnitudes of M5.8 in the WUS (Figure 4, page 13 ). The observations physically confirmed the lower attenuation of seismic waves in the EUS. Directionality was evident in this effect as well, with the affected area having an ellipsoidal shape, with lower attenuation parallel to the rupture. A few small liquefaction sand boils within Mineral were identified by the GEER team [4]. Soil effects due to the sharp stiffness contrast between soil and rock was evident. Other potential geotechnical evidence likely disappeared due to heavy rains from Hurricane Irene that followed shortly after the earthquake.

Non-Structural Components and Downtime

ADVERTISEMENT–For Advertiser Information, visit www.STRUCTUREmag.org

The earthquake tied up phone and internet connections, disrupted rail lines, and

220

Structural Design Spreadsheets

Accurate

Just input in green highlighted cells; the spreadsheet and VBA program do the calculations.

Helpful

Each spreadsheet includes drawings and code references; Copy/Paste results to AutoCAD; Quick-Link, see “What Is New?” at top of website homepage.

Prompt

Technical Support, Software Updates (emailed).

www.Engineering-International.com

Coupon for Package: $120 off Code: ASCE 7-2010

caused extensive traffic delays and business disruptions as far away as New York City.

Non-structural components were affected, as seen in photos from the Louisa County High School (Figure 5). This could be expected since the immediate epicentral region would fall under low Seismic Design Categories that do not require significant non-structural components detailing.

Response & Awareness The earthquake caused widespread response confusion between public and emergency personnel, all of whom exhibited a lack of preparedness. Evacuation and rapid assessment procedures were either inconsistent or completely absent, even in medical facilities. Cell phone service and public transportation were disrupted, while airports and train stations were shut down immediately to assess damage.

Several office buildings, including some in New York City (NYC), were evacuated. Social media were extensively used to communicate facts and experiences. Within 4 minutes of the quake, the word “earthquake” appeared in 3 million status Facebook updates. The Twitter rate was 5,500 messages/second, a rate similar to that seen immediately following the Tohoku mega-earthquake and tsunami [5].

Code Implications & Needs for Improvement Lessons from the 2011 VA Earthquake can be used to revisit and improve certain code concepts and requirements for the EUS. Seismic Hazard The low decay and high frequency content of rock ground motions are taken into consideration in developing seismic hazard maps by using regional Ground Motion Prediction Equations (GMPEs) that estimate ground motion characteristics of PGA and SA as a function of magnitude and distance from

STRUCTURE magazine

14

March 2013

the earthquake source. Due to the scarcity of recorded strong motions, GMPEs are mostly empirical or stochastic and, as a result, their predictions can vary significantly. For instance, SA predictions for a structure with period of 1 second for a typical M6.0 earthquake located at a site 10 miles from the epicenter, can vary from 0.03 g to 0.11 g, a difference of more than 300%. To address this very large variability, engineers usually resort to a relative weighting of the GMPEs and have to select hazard predictions significantly higher than the mean. A better consensus in the scientific community on regional GMPEs is needed for practical applications.

Site Effects & Classification The applicability of code-based site coefficients, Fa and Fv, has been discussed extensively in this magazine [6,7]. Generic code site coefficients may not be representative of the behavior of regional soils, due to two main factors: (a) the sharp stiffness contrast of overburden soils with very hard bedrock, and (b) the bedrock motions, expected to be of relatively short duration, high frequency, and moderate intensity. Hence, if the soil is soft above the bedrock at shallow depths (say less than 100 feet), there will be resonance in the short period range, affecting mostly “short” or “stiff” structures with the relevant Fa code coefficient underpredicting soil amplification.

Indicatively, let’s assume a simple, shallow cohesionless soil profile with a code-classification of Site Class C or D, with a depth to regional hard bedrock (H) varying from 15 feet to 90 feet and with equivalent periods from 0.2 seconds to 0.6 seconds. The profiles were subjected to motions representative of the hazard in the NYC metropolitan area using the American Society of Civil Engineers’ (ASCE) Minimum Design Loads for Buildings and Other Structures, ASCE 7-05, guidelines [8]. Figure 6 shows that the equivalent Fa (orange lines) from the site-specific response is higher even than the highest code values [2].

Hurricane Sandy. Although ASCE 7-10 is an improvement towards performance and riskbased design, which should be welcomed in the EUS, a consideration of threshold limits for SDCs could be revisited to reflect EUS intensities of motions.

Actions for the Future and Conclusions Figure 6: Equivalent site coefficient, Fa , and comparison with code-based Fa for a parametric study of idealized Eastern US sites (modified from Nikolaou et al, 2012).

Moreover, the site classification procedure is not appropriate in this case, as code guidelines allow for the inclusion of rock in site classifications of shallow sites. Specifically, ASCE 7-05 and ASCE 7-10 [8], Section 20.4 states: “Profiles containing distinct soil and rock layers shall be subdivided into... a total of n distinct layers in the upper 100 feet.

Where refusal is met for a rock layer, Ni shall be taken as 100 blows/ft.” This allowance of incorporating a simulated rock layer as soil can lead to a “stiffer” more favorable site class with even lower Fa as compared to the classification using soil properties alone.

The importance of local geology, and the implications of being unconservative when generic procedures are followed, give timely opportunity for code modifications that can be complemented with data from the few valuable records from the 2011 Virginia Earthquake.

to the intensity and associated damage from the WUS data recorded, such as for the 1994 Northridge Earthquake, and are not necessarily applicable in the EUS, as the 2011 VA Earthquake intensity distribution has shown (Figure 1). Several large cities have seismic coefficients that are on the borderline with threshold limits between SDCs. With the new generation of codes modeled after ASCE 7-10 [8], the basis for design is shifted from a uniform hazard (same probability of an earthquake to happen) to a uniform risk (same probability of a structure to collapse), using risk-targeted instead of hazard seismic maps. Once the map values are identified, subsequent procedures for determining SDCs and seismic loads remain practically unchanged, with an estimated reduction on the order of 10% to 15% as compared to ASCE 7-05. Such reductions are sufficient to classify sites into a lower SDC [9], hence requiring less seismic detailing. Using ASCE 7-10, many Seismic Design Requirements SDC’s would be reduced by one level in the Seismic Design Category (SDC) defines the Table below. required level of seismic structural analysis Although these SDC comparisons are not and construction detailing for structural and direct because of the difference in design non-structural components, including electri- philosophies, the practical impact is a gencal and mechanical equipment. It depends on eral lowering of SDCs in the Eastern United the structural Occupancy Category (OC) and States. The relaxation of detailing requiredesign acceleration levels [6]. In the EUS, the ments can impact the post-earthquake SDC ranges from “A” to the strictest “D.” The function of structures. Damage may be higher threshold design seismic coefficients values for in non-structural components, such as ceilingeach SDC (ASCE 7, Section 11.6) are based suspended electric/mechanical systems, that upon the correlations of these coefficients can affect the time needed for a structure to be serviceable after an earthquake Typical regional shift (shaded in gray) in Seismic Design (downtime), even in the absence Category (SDC) when moving from ASCE7-05 to of significant structural damage.

ASCE7-10 code basis.

This is particularly important for SEISMIC DESIGN CATEGORY large cities with high population ASCE7-05 vs.

ASCE7-10 densities, whose downtime can Structural Site Class have detrimental effects in their Occupancy economy as well as the nation’s A D E B C Category overall economy, as we saw followI/II B A B B C B D C ing the 2011 VA Earthquake and III B A B B C B D C in the dramatic effects of the 2012 IV C A C C D C D D STRUCTURE magazine

15

March 2013

Because the Eastern United States is a region with moderate but highly unpredictable earthquake activity combined with a large percentage of structures lacking adequate seismic design, it is exposed to a high seismic risk with potentially significant socioeconomic effects. The 2011 Virginia Earthquake was a reminder that earthquakes do happen in this region and are felt at very large distances. It confirmed earlier scientific understandings and historic experiences that regional soils, bedrock, and earthquake motions have unique characteristics that warrant a reconsideration of the overall approach to seismic hazard and associated risk [10] and emergency response preparedness, and a revisit of code procedures for site classification and design and construction requirements.

Moving forward, practitioners and researchers agree on the need to update regional seismic analysis and design standards to reflect new science and engineering knowledge. Work is under way on a variety of topics, including: (i) the Next Generation Attenuation (NGA-East) research project is developing consensus ground motion prediction (or attenuation) equations, seismic hazard assessments, and characterizations of site responses (scheduled for 2014 [11]); (ii) the Earthquake Engineering Research Institute (EERI.org) has recently established four local chapters with goals to bring awareness and education at all levels of expertise (engineering, geoscience, architecture, planning and social science) and to focus on reducing earthquake risk; (iii) the Multidisciplinary Center for Earthquake Engineering (MCEER.buffalo.edu), in collaboration with the Structural Engineering Association of New York (SEAoNY.org), has initiated studies to better understand vulnerabilities of typical, older NYC masonry construction; (iv) the American Society of Civil Engineers (ASCE.org) is updating the risk-targeted provisions of ASCE 7-10, with modifications for regional ground motions and soils effects.▪ The Author gratefully acknowledges the interaction with and material provided by her EERI, GEER, MCEER and ASCE collaborators, as well as contributions from her colleagues at Mueser Rutledge Consulting Engineers.

Practical SolutionS solutions for the practicing structural engineer

H

istorically, equivalent static analysis procedures have been used to determine seismic design forces for conventional structures. In certain situations involving critical or highly complex structures, modal analysis procedures utilizing the elastic response spectrum concept have been employed. Both of these analysis procedures are computationally inexpensive yet they can be overly conservative. Recently, with the advent of performance-based seismic design concepts coupled with the significant advances in computing technology, the structural engineering community has shown a growing interest in seismic response history analysis. What has not been well documented is a clear procedure to find, select, and scale seismic time histories for use in a code-based design. This article outlines one such procedure that will enable a design engineer to access seismic time history databases, select the appropriate time histories for a given site and structure, scale these histories to ASCE 7 levels, and create a design based on ASCE 7 Chapter 16 procedures.

Seismic Time Histories A Practical Approach

By Kyle D. Harris, P.E, Nicholas D. Robinson, P.E. and Eric L. Sammarco, P.E.

Kyle D. Harris, P.E. is a staff engineer at Kiewit Power Engineers Co. He can be reached at kyle.harris@kiewit.com.

Nicholas D. Robinson, P.E. is a staff engineer at Kiewit Power Engineers Co. He can be reached at nicholas.robinson@kiewit.com.

Eric L. Sammarco, P.E. is currently pursuing a Ph.D. in Structural Engineering at the University of Texas at Austin. He can be reached at esammarco@utexas.edu.

The online version of this article contains additional material. Please visit www.STRUCTUREmag.org.

Selecting Ground Motion Histories Perhaps the most important and challenging step in a seismic response history analysis is the proper selection of input ground motion histories to be used for subsequent dynamic analysis. It is highly recommended that both the structural and geotechnical engineer – and even a seismologist in some cases – participate in the selection process, as there are many multidisciplinary aspects that warrant consideration. Although the general, qualitative procedure for selecting appropriate input ground motion histories is essentially the same for any site, there are many quantitative details and nuances that can be specific to the governing regulatory documents and/or building codes as well as the specific site of interest.

As such, this article will focus predominately on the general procedure.

Earthquake induced ground motion histories are non-periodic and highly nonlinear digitized curves that represent the kinematic response of a fixed point in the propagating medium or on the ground surface. The ground motion histories are influenced by things such as the characteristics of the seismic source, the fault rupture process, the geologic medium through which the seismic waves are propagating, and local site conditions. Fortunately, it is not necessary to predict every peak and trough of a ground motion history derived from a postulated earthquake event in order to successfully analyze and design

16 March 2013

a structure. Rather, it is necessary to identify key ground motion parameters that adequately reflect the characteristics of the ground motion: the amplitude, duration, and frequency content of the motion. The peak horizontal acceleration is historically the most popular amplitude parameter used to describe a ground motion – largely due to its inherent relationship with inertial forces.

Ground motion duration is another important parameter that tends to get less attention than others, and can have a significant influence on structural damage. The most common duration parameter is arguably the bracketed duration, which is defined as the time between the first and last exceedance of a threshold kinematic response quantity. The frequency content of a particular ground motion provides information about relative energy demand as a function of individual signal frequencies, and it can be most clearly depicted in a Fourier amplitude spectrum.

Another measure of frequency content that is often employed in the commercial nuclear energy industry is the power spectrum or power spectral density function (e.g., ASCE 4-98). By far, the most popular frequency domain spectrum utilized in earthquake engineering practice is the elastic response spectrum (ERS). An ERS describes the maximum elastic response of a single-degreeof-freedom (SDOF) system to a given ground motion history as a function of the SDOF system’s natural frequency and critical damping ratio. The ERS contains a spectral response quantity on the ordinate axis (spectral acceleration, velocity, or displacement) and SDOF system natural frequency or period on the abscissa axis. Although the ground motion characteristics are filtered by the response of the SDOF system, it is important to point out that the amplitude, frequency content, and (to a lesser extent) duration of the input ground motion are all reflected in the spectral response values.

The first step in the general procedure for selecting ground motion histories is to conduct a seismic hazard analysis to determine the control points of the design basis ERS (e.g., ASCE 7-10 Fig. 11.4-1). For typical structures located on geologically favorable sites, the seismic hazard analysis and determination of the design basis ERS control points can be done per the ASCE 7-10 Section 11.4 provisions along with the seismic ground motion long-period transition and risk coefficient maps of ASCE 7-10 Chapter 22.

This process can be expedited by utilizing the United States Geological Survey’s U.S. Seismic Maps Web Application. For critical facilities, such as disaster response facilities and mission-critical military structures or structures located on soils vulnerable to potential failure or collapse under seismic loading (e.g., liquefiable soils), a rigorous site-specific probabilistic seismic hazard analysis and site response analysis may be required. continued on page 18

Spectral Acceleration Response Spectrum

Scaled w/ Design Spectrum

ζ = 5%

2.5

2 Spectral Acceleration (g)

Once the design basis ERS is established, the next step is to obtain or generate ground motion histories that possess sufficiently similar ground motion characteristics as those exhibited by the design basis ERS. The most common method to measure compatibility between the ground motion histories and the design basis ERS is to overlay the ground motion history ERS with the design basis ERS (Figure 1). Most building codes and regulatory documents acknowledge the uncertainties associated with “seismically similar” ground motion histories by requiring more than one set of ground motion histories to be considered during analysis. Ideally, actual recorded ground motion histories from recording stations near the site of interest exist. A detailed list of websites containing national and international strong motion data can be found on the MCEER website. When this is the case, these baseline histories should first be compared with the design basis ERS. If adequate compatibility is not achieved, then the ground motion histories can be carefully scaled to fit the tolerances of the design basis ERS. If no suitable ground motion data exist, then the generation of synthetic ground motion histories is usually permitted.

A synthetic ground motion history can be developed in one of three ways: time domain generation, frequency domain generation, or

by Green’s Function techniques. For a more thorough treatment of ground motion selection and scaling, it is recommended that the NIST GCR 11-917-15 Selecting and Scaling Earthquake Ground Motions for Performing Response-History Analyses be consulted.

SITE SPECIFIC PARAMETERS NORTHRIDGE ‐ TARZANA IMERIAL VALLEY ‐ EL CENTRO

1.5

TOKACHI‐OKI ‐ HACHINOHE SAN FERNANDO ‐ CASTAIC HYOGO‐KEN‐NANBU ‐ KOBE 1

CHILI ‐ LLOLLEO KERN COUNTY ‐ SANTA BARBARA WESTERN WASHINGTON ‐ SEATTLE MIYAGI‐KEN‐OKI ‐ SENDAI

0.5

KERN COUNTY ‐ TAFT

0 0

0.5

1

1.5

2

2.5

3

3.5

4

Period (sec)

Figure 1: Example elastic response spectrum.

where, u(t) is the relative displacement of the SDOF system with respect to the ground displacement, ag(t) is the ground acceleration, ω is the SDOF natural frequency (rad/sec), and ξ is the SDOF critical damping ratio. The relative displacement and ground acceleration are both functions of time corresponding to the history’s recorded time steps. There exists a large body of knowledge regarding solution methods for various types of differential equations. For purposes of this article, only two common methods useful in dynamic response analysis will be briefly discussed; the Central Difference Method (CDM) and the Newmark Method. The CDM is probably the most common explicit numerical integration technique employed to solve dynamic response problems, but it is only conditionally stable – meaning that if the selected time step is not short enough then the solution will diverge rendering erroneous results. The Newmark Method is an implicit numerical integration technique, and it is unconditionally stable when the average acceleration approach (as opposed to the linear acceleration approach) is taken.

Both methods are presented in detail in almost any structural dynamics text, but they are only introduced here to assist in understanding the creation of an ERS. An example using Newmark’s Average Acceleration Method demonstrating the required steps to develop an ERS can be found in the online expanded version of this article. The example will provide the readers with definitions of terms, useful relationships and initial calculations to aid in the development of an ERS for a specific acceleration time history.

ASCE 7-10 Code Requirements

Once an ERS has been created from a selected ground motion history, the engineer can begin to compare the record to a code level event.

Different histories will create vastly different ERS’s due to the natural variation of frequency and acceleration content within the records themselves. This will typically result in a highly variable response spectrum (unlike the smoothed spectrum found in Section 11.4.5 of ASCE 7-10). The general shape of the response spectrum for most records will share a shape similar to the design spectrum (for certain records, however, this is not the case, and significant deviations from the design spectrum are possible).

Given the rarity of Maximum Considered Earthquake (MCE) level events, it is common to scale specific acceleration records to match Developing an Elastic an MCE level event for a given site. Many different techniques for scaling records exist, Response Spectrum each with their own benefits and drawbacks.

Once the ground motion histories have been The available techniques largely fall into two selected or synthetically generated, the ground broad categories; techniques that modify the motion ERS’s are computed and compared frequency content of a record and those that to the design basis ERS to ensure their comdo not. Of the two categories, techniques patibility. As discussed previously, an ERS which allow modification of the frequency describes the maximum elastic response of content are much more demanding and hence an SDOF system to a given ground motion beyond the scope of this article. To this end, history. The equation of motion can be solved the authors will focus on the application of a using numerical time integration methods simple uniform amplitude scale factor which where the equation is integrated using a stepgenerally produces satisfactory results. by-step procedure. The equation of motion Aligning the ground motion history ERS to be solved numerically can be cast as shown within a code-specified tolerance of the design in Equation 1, basis ERS control points ensures similarity in ground motion amplitude, frequency content, d u(t) + ω2u(t) = – a (t) d—2 u(t) + 2ωξ — g and duration. Per Section 16.1.3.2 of ASCE dt 2 dt (Equation 1) 7-10, “Each pair of motions shall be scaled such that in the period range from USGS Seismic Maps: (http://geohazards.usgs.gov/designmaps/us/) 0.2T to 1.5T, the average of the MCEER: (http://mceer.buffalo.edu/infoservice/reference_services/strongMotionGuide.asp#1) SRSS spectra from all horizontal STRUCTURE magazine

18

March 2013

1.5T

∫0.2T[f (x)–n * g(x)] dx  0 (Equation 2) where, f(x) is the design basis ERS, g(x) is the averaged ground motion ERS, and n is the scale factor. After the selection of an initial scale factor, small adjustments can be made to meet the provisions of Section 16.1.3.2 of ASCE 7-10. It is worth noting that the use of large scale factors (the authors suggest n ≤ 5 as a rule of thumb) should be avoided if possible. The validity of a record that requires a very large scale factor is somewhat reduced, especially when the source mechanism is not consistent with the MCE level event.

Once a record has been selected and scaled to the appropriate level, it can be used to perform a code level analysis and/or design. Chapter 16 of ASCE 7-10 recognizes two primary methods of response history analysis: linear and nonlinear.

A linear analysis requires additional scale factors to be applied to the analysis results whereas the results of a nonlinear analysis do not require

additional scaling. Per Section 16.1.4 of ASCE 7-10 for a linear analysis, “force response parameters shall be multiplied by Ie /R” and “Drift quantities shall be multiplied by Cd /R.” These factors approximate the effects of material nonlinearity that are not captured directly by the linear analysis. Additionally for a linear analysis, “where the maximum scaled base shear predicted by the analysis, Vi, is less than 85 percent of the value of V determined using the minimum value of C s set forth in Eq. 12.8-5 or when located where S1 is equal to or greater than 0.6g, the minimum value of C s set forth in Eq. 12.8-6, the scaled member forces, QEi , shall be additionally multiplied by VV .” This factor is meant to i safeguard from inappropriately flexible building models (and other analysis errors) leading to artificially low base shears.

For both linear and nonlinear analysis, if at least seven ground motions are analyzed then it is acceptable to use average response values for design. If fewer than seven ground motions are analyzed – ASCE 7-10 requires a minimum of three ground motions – then the maximum response values must be used for design. When performing a three-dimensional analysis, these ground motions should consist of horizontal matched pairs selected based on the aforementioned statistical requirements.

For a two-dimensional analysis, these ground motions shall consist of a single horizontal ground motion history.

The use of the seismic overstrength factor (Ω0) is also modified when performing a response history analysis. Chapter 16 of ASCE 7-10 contains two different provisions regarding the use of the seismic overstrength factor depending on whether a linear or nonlinear analysis is performed. Per Section 16.1.4 of ASCE 7-10, the seismic load effects including the over strength factor for a linear analysis need not be taken larger than the maximum unscaled value obtained from the linear analysis. Per section 16.2.4.1 of ASCE 7-10 for a nonlinear analysis, “the maximum value of QEi obtained from the suite of analyses shall be taken in place of the quantity Ω0QE.” This can have a significant effect on the design of a structure located in a region of high seismic risk.

Conclusion The provided commentary, external references, and examples have been assembled in an attempt to raise awareness in those engineers who stand to benefit from the use of seismic response history analysis. It is the hope of the authors that this article will provide the reader with an increased awareness of seismic response history analysis and serve to diminish the perceived barriers to its use.▪

STRUCTURE magazine

19

March 2013

CONSTRUCTION CEMENT

FA S T ER STRONGER MORE DURABLE 3000 PSI IN 1 HOUR

Specified Worldwide

ADVANCED TECHNOLOGY • High bond strength • Low shrinkage • High sulfate resistance • Great freeze thaw durability • Long life expectancy • 65% lower carbon footprint

Available in Bags and Bulk

800-929-3030 ctscement.com

ADVERTISEMENT–For Advertiser Information, visit www.STRUCTUREmag.org

component pairs does not fall below the corresponding ordinate of the response spectrum used in the design.” As described earlier in this article, an ERS must first be created for each record using 5 percent critical damping.

The response spectrum ordinates of the two component pairs of each record must then be combined using the square root of the sum of the squares (SRSS) method. The ordinates of these new SRSS spectra for each set of component pairs are then averaged together to create a single averaged ground motion ERS. This averaged ground motion ERS is then compared to the design basis ERS of Section 11.4.5 of ASCE 7-10. Scale factors are then selected and applied to the ordinates of each pair of records to ensure that the ordinates of the averaged ground motion ERS do not fall below the design basis ERS within the period range of 0.2T to 1.5T. It should also be noted that when dealing with two orthogonal horizontal component motions for use in a coupled 3-dimensional dynamic analysis, it is often required that one component motion be statistically independent from the other. For example, when selecting/developing ground motion histories for a commercial nuclear energy facility, ASCE 43-05 requires that the directional correlation coefficients between pairs of records be less than or equal to 0.30.

Although ASCE 7-10 provides no specific guidance on the selection of individual scale factors, and an engineer could conceivably meet the provisions by applying a very large scale factor to a few records and a small factor to the remaining records, this is not in agreement with the general intent of the provisions. The authors recommend selecting an initial scale factor that satisfies the following relationship:

Codes and standards updates and discussions related to codes and standards

Why a Code?

In March 2012, the International Code Council (ICC) published the first edition of the International Green Construction Code TM (2012 IGCC TM ). The need for the development of a code-enforcable set of green building requirements arose from the fact that, throughout the U.S., LEED® certification of buildings was increasingly mandated by government. But as a voluntary, choice-driven rating system, LEED is ill-suited to enforcement by local building codes.

Thus, the IGCC was developed as a mandatory language, overlay model code that contains a minimum set of requirements for green buildings that is easily adoptable by jurisdications. The IGCC is intended to be adopted in conjuction with the other I-codes, including the 2012 International Building Code (IBC) and the 2012 International Energy Conservation Code (IECC). Numerous jurisdictions throughout the U.S. have already adopted the 2012 IGCC, in whole or in part.

The content of the 2012 IGCC is roughly equivalent to a codified version of the 2009 Leadership in Energy and Environmental Design (LEED®) for New Construction rating system at a basic level. Jurisdictional requirements and project electives allow for the addition of optional requirements to be implemented. The following describes these options as well as provisions most likely of interest to the structural engineer.

The International Green Construction Code What You Need to Know

By Christine A. Subasic, P.E., LEED AP

Scope and Organization The 2012 IGCC is organized into 12 chapters and 4 appendices (see Table). The IGCC applies Christine A. Subasic, P.E., LEED AP is a consulting architectural engineer and owner of C. CALLISTA SUBASIC in Raleigh, NC. She provides technical support in the area of masonry and sustainable design, including educational seminars, standards development, technical writing, and inspection services. She can be reached at CSubasicPE@aol.com.

The online version of this article contains detailed references. Please visit www.STRUCTUREmag.org.

to all occupancies, except temporary structures.

Most low-rise residential structures are excluded, unless the jurisdiction specifically chooses to include them and then the requirements of the National Green Building Standard (ICC 700) apply. Section 101 of the IGCC also recognizes ASHRAE Standard 189.1-2011, Standard for the Design of High-Performance Green Buildings Except Low-Rise Residential Buildings, as an alternate compliance path.

Jurisdictional Requirements Chapter 3 of the IGCC contains requirements that are “specific to and selected by” the jurisdiction. Table 302.1 is used to indicate requirements selected, which are in addition to the minimum provisions of the IGCC. Once chosen, these provisions are to be enforced as mandatory requirements. Requirements in Table 302.1, of interest to structural and civil engineers, include: • inclusion of residential buildings with corresponding compliance with ICC 700; • whether construction in flood hazard areas is excluded; • whether construction near surface water (such as lakes, rivers, etc) is excluded; • whether construction on greenfield sites is excluded. Greenfields are identified in the IGCC as areas without existing infrastructure and/or not near public transit and the like.

• the minimum percentage of construction waste that must be diverted from landfill; • whether acoustic requirements apply; and • whether enhanced energy efficiency is desired.

Chapter 3 also contains the option for whole building life cycle assessment (LCA). If a whole

Organization of the 2012 IGCC.

Chapters 1-2

Subjects Administration and definitions

3

Jurisdictional requirements and life cycle assessment

4

Site development and land use

5

Material resource conservation and efficiency

6

Energy conservation, efficiency and CO2e emission reduction

7

Water resource conservation, quality and efficiency

8

Indoor environmental quality and comfort

9

Commissioning, operation and maintenance

10

Existing buildings

11

Existing building site development

12

Referenced standards

Appendix A

Project electives

Appendix B

Radon mitigation

Appendix C

Optional ordinance

Appendix D

Enforcement procedures

20 March 2013

building LCA is performed in accordance with the provisions of Section 303.1, the material requirements of Section 505 do not apply. Section 303.1 (LCA) requires a 20% improvement “… in environmental performance for global warming potential and at least two … impact measures, as compared to a reference design….” The impact measures to be evaluated are primary energy use, acidification potential, eutrophication potential, ozone depletion potential, and smog potential. As the building structure constitutes a significant portion of the environmental impact for many buildings, the structural engineer must work closely with the design team and the LCA consultant if this approach is pursued.

Project Electives Project electives are found in Appendix A of the IGCC. These provisions are not mandatory unless specifically referenced in the adopting ordinance. This appendix provides “…a basis by which a jurisdiction can implement measures to increase natural resource conservation, material resource conservation, energy conservation, water conservation and environmental comfort and mitigate impacts of building site development.” The jurisdiction must specify the minimum number of project electives required in each of the areas of the site (Table A104), materials (Table A105), energy (Table A106), water (Table A107), and indoor environment (Table A108). Zero electives can be specified.

Though similar to jurisdictional requirements in that they allow the jurisdiction to tailor the IGCC to their locale, project electives allow the owner/design team flexibility to choose specific project electives for the project. Selected project electives are then treated as mandatory (code) requirements.

Project electives of interest to the engineer are discussed herein.

Site Development and Land Use Chapter 4 contains requirements related to site development and land use. Specifically, this chapter contains mandatory requirements for stormwater management, paved walkways and bicycle paths, changing and shower facilities, and requirements to mitigate the heat island effect, in addition to jurisdictional requirements for site development restrictions previously listed. Of particular note is the heat island mitigation requirement in Section 408.2 that 50% of hardscape areas be either

Figure 1.

constructed of materials with a solar reflectance of 0.30 or more, be provided shade by a structure or tree, or be pervious or permeable pavement. If shading by structure is chosen, the structural engineer may be required to design free-standing structures such as covered walkways or trellis (Figure 1) or roof structures such as covered parking. In addition, Section 408.3 requires that roofs meet requirements for heat island mitigation, which may include use of a vegetative roof. Such roofs present a number of issues that must be addressed by the structural engineer and design team, including type of vegetation, imposed structural loads, waterproofing and roof slope.

Material Resource Conservation and Efficiency Many of the provisions in Chaper 5 on material resource conservation are similar to the provisions found in the LEED rating system.

Unless whole building LCA is chosen, Section 505 Material Selection requires that at least 55% of the building materials (calculated by mass, volume or cost) comply with one or more of the criteria listed below. Materials meeting multiple criteria can be counted multiple times. For example, if a used (salvaged) material is selected that comes from a source within 500 miles (800 km) of the building site, that material can be counted two times its amount because it complies with two provisions. The criteria are: • Used materials and components.

• Recycled content building materials.

These must either: o contain at least 25 percent combined post-consumer and preconsumer recovered material, and meet the recycable materials provisions, OR o contain not less than 50 percent combined post-consumer and preconsumer recovered material.

STRUCTURE magazine

21

March 2013

• Recycable materials and components.

These must either: o be recycled into the same material or another material with a minimum recovery rate of not less than 30% through recycling and reprocessing or reuse, OR o be recyclable through an established, nationally available closed loop manufacturer’s takeback program.

• Bio-based materials. These must comply with one or more of the following: o bio-based content is not less than 75 percent as determined by ASTM D6866. o wood and wood products (other than salvaged or reused wood products) must meet labeling requirements. o federal procurement requirements (USDA 7CFR Part 2902) for designating bio-based products.

• Indigenous materials. These must be recovered, harvested, extracted and manufactured within a 500 mile (800 km) radius of the building site.

Like LEED, only that portion of the material that meets this requirement can be included in the calculation.

However, unlike LEED, for materials transported by rail or water “the distance to the building site shall be determined by multiplying the distance that the resources are transported by water or rail by 0.25, and adding that number to the distance transported by means other than water or rail.”

Though structural material selection depends on numerous factors beyond the criteria listed in Section 505 of the IGCC, these criteria should be among those considered for evaluation by the engineer when determining the structural system to be used. Because the

and construction documents. If this project elective is chosen, care must be taken when selecting not only the materials used, but also the structural connections chosen (i.e. bolted versus welded connections).

Appendix A also contains project electives for reuse of an existing building (A105.6) and reuse of an historic building (A105.7).

Figure 2.

criteria in Section 505 are fairly broad, it is likely that most structural systems will be able to make a positive contribution toward meeting the requirements of this section.

Material Project Electives Several of the material resource and conservation project electives found in Appendix A, Section A105, simply require an enhanced level of performance for many of the provisions found in Chapter 5. However Section A105 also contains several items of interest to the engineer.

One unique addition is the construction waste landfill maximum project elective (A105.2). This project elective, if chosen by the owner, limits the total construction waste, excluding hardscape waste, disposed of in a landfill to no more than 4 pounds per square foot of building area. The structural engineer can help meet this requirement by designing for structural efficiency, selecting structural materials with little waste and keeping the modular nature of many building materials in mind. In addition, selecting materials that can serve as both structure and finish helps to further reduce the amount of resources used.

Another project elective of interest is the building service life plan project elective (A105.4). This elective requires a building service life plan that indicates the intended design service life (in years) for the building “…as determined by the building owner or registered design professional…” and must include a maintenance, repair, and replacement schedule for major elements of the building, including the structural elements and major materials and assemblies.

Structural engineers should also be aware of the design for deconstruction and building reuse project elective (A105.5). This project elective requires that buildings be “…designed for deconstruction of not less than 90 percent of the total components, assemblies, or modules to allow essentially the entire building to be reused.” The design for deconstruction must be documented on the building’s plans

Energy Conservation, Efficiency and CO2e Emission Reduction Chapter 6 contains requirements related to energy efficiency and CO2 emission reduction.

This chaper offers two compliance paths: a performance-based approach utilizing energy modeling and a prescriptive approach. Others have written of the effects of structural connections and penetrations through the building envelope on energy performance of the building. However, the prescriptive provisions found in Section 605.1.1 are worth discussion here.

This section requires permanent, horizontally projecting shading devices on specified vertical fenestration. The specific requirements and exceptions are found in Section 605.1.1.1.

For the structural engineer, this translates to exterior accessories, such as light shelves, that will likely require structural support and coordination (Figure 2).

Energy Project Electives The passive design project elective (A106.5) is of potential interest to the structural engineer.

This elective requires that at least 40% of the annual energy use reduction realized by the proposed design be achieved through passive heating, cooling, and ventilation design.

Passive strategies that may affect the structural design include building orientation, fenestration provisions, material selection, overhangs, shading means, passive cooling towers, natural heat storage, and thermal mass.

Water Resource Conservation, Quality and Efficiency Most of Chapter 7 on water conservation does not affect the structural design, though Section 707 does contain requirements related to rainwater collection and storage. The IGCC does not require rainwater collection, but rather specifies criteria for buildings that include collection systems. The structural engineer should be aware that rainwater catchment systems may dictate slopes of slabs, and collection systems

STRUCTURE magazine

22

March 2013

such as cisterns may impose significant loads on the structure. Likewise, gray water storage tanks (Section 708 and Section A107.9) may be located above- or below-grade and can contribute significant structural loads.

Indoor Environmental Quality and Comfort When required by the jurisdiction, Section 807 specifies acoustic performance requirements. These requirements dictate the minimum sound transmission class (STC) levels for wall and floor-ceiling assemblies based on the occupancy of the spaces being separated. Though the building structural frame is not directly affected, the design of the bearing and nonbearing walls, as well as the floor system, is of interest. Heavy materials such as concrete and masonry are likely to meet the STC requirements of Section 807 utilizing typical means and methods of construction. However, typical cold-formed steel and gypsum board wall construction does not meet the STC requirements. In this case, multiple layers of gypsum board, insulation, or special clips may be required in order to meet the specified STC ratings.

Wall systems and flooring are also subject to VOC emission limits found in Section 806.

Table 806.4(1) and Table 806.5(1) list materials that are deemed to comply for floors and walls/ceilings respectively, including ceramic and concrete tile, clay masonry, concrete masonry, concrete and metal. These requirements may influence the materials chosen for interior structural walls and floors, particularly when selected as mandatory provisions as part of the indoor environment project electives (A108.2, A108.3, and A108.4).

Daylighting is required by the IGCC for several occupancy groups. Section 808 contains the specific requirements. The structural engineer should be attuned to the potential impact on the structural design of large areas of glazing that may be included, such as clerestories and skylights.

Conclusion While at first glance the International Green Construction Code might seem to have little to do with structural design, closer examination reveals numerous provisions that the structural and civil engineer should be aware of. By familiarizing oneself with the requirements discussed in this article, the structural engineer can become a valuable contributor to the discussion and selection of green building strategies.▪

What Gives?

The patented Yield-Link™ structural fuse, that's what.

As the latest innovation from Simpson Strong-Tie, the Strong Frame ® special moment frame features four Yield-Link structural fuses that eliminate lateral-beam bracing and are replaceable after a major seismic event. What’s the advantage? It’s easier to specify and it can save building owners significant cost. As with our other moment frames, there is no welding, only bolted connections.

Learn more by calling (800) 999-5099 or visiting www.strongtie.com/smf.

Code Listed: ICC-ES ESR-2802

© 2013 Simpson

Strong-Tie Company Inc. SMF13

Masonry has a New Edge.

And it’s called HALFEN FK4.

Introducing a new adjustable shelf angle with a thermal break.

H

ALFEN FK4 brickwork supports transfer the dead load of the outer brick veneer to the building’s load-bearing structure: an efficient construction principle developed with the experience of over 80 years of lasting technology.

Adjustability HALFEN FK4 brickwork supports provide continuous height adjustment of +/- 13/8” which compensates existing tolerances of the structure as well as installation inaccuracies of wall anchors.

Efficient Design As the demand for higher energy efficiency in commercial buildings continues to increase, the cavity between the brick veneer and the substrate is getting larger to allow for more insulation and air space. Along with this increased cavity size, the traditional masonry shelf angle, used to support the brick veneer at the slab edge, is also getting larger and subsequently heavier and more expensive to install. Architects & Engineer are looking for a more efficient support solution. The HALFEN FK4 brickwork supports use a thinner light weight shelf angle, eliminating brick notching while also providing a wider cavity.

Structural Efficiency From load capacities starting at 785 lbs up to 2,360 lbs, the HALFEN FK4 brickwork supports allow efficient anchoring of brickwork facades in connection with HALFEN cast-in channels.

Reduced Thermal Bridging The HALFEN FK4 brickwork supports are off set from the edge of slab. Minimal contact with the building structure means reduced thermal bridging and lower energy loss.

Quality By using HALFEN FK4 brickwork supports, you profit from an approved anchoring system, excellent adjustment options and a complete product program covering all aspects of brickwork facing.

Many advantages with one result: HALFEN provides safety, reliability and efficiency for you and your customers.

Halfen Anchoring Systems · Meadow Burke Products · PO Box 547 Converse, TX 78109 · Phone: 800 323 68 96 · www.halfenusa.com · info@halfen.com

This article makes the case that the use of a Geotechnical Engineer for his/her engineering expertise could be more advantageous to the design team than a request for just low-cost drilling and a cheap Geotechnical Report.

Background As the Structural Engineer for a building, how many times have you received from an owner a so-called “Geotechnical Report” that in your opinion was worth just slightly more than the paper on which it was written? Chances are, more than once.

Why was there a lack of value? Most likely, the report was written in a vacuum, without any specific communication between the Geotechnical and Structural Engineers. Most likely it was commissioned by an owner with requirements for low cost and fast turn-around time. Why the Owner? AIA documents clearly state that this is an Owner’s furnished item.

Let us return to the so-called “Geotechnical Report”. What do you do now? For starters, you may pick up the phone and call the Architect to get permission to contact the Geotechnical Engineer with your specific questions. Let’s assume you get the O.K. Depending on your relationship with the Geotechnical Engineer, you may get some specific answers or you may hear the phrase: “That will cost you....$”. Now you are stuck. You have to call the Architect to get the Owner’s approval for the additional payment. (Note: There is nothing wrong with asking to be paid for your services above and beyond the original contractual obligations. Since the Geotechnical Engineer met the initial Owner’s criterion of low price, he/she should not be expected “to give away the store”. ) In most instances, the Owner is not too happy; and, since the job is still in its early stages, neither is the Architect.

Even if you, the SE, were requested to provide some input for the Request for Proposal (RFP), it usually is limited to the boring locations and number/depths of borings, and the Owner will take care of the rest. If that is all that you are asked to provide, the results are not going to be that much different from those previously described.

When AIA G-602 is used as the basis for the RFP, contractual aspects are well covered. Structural requirements are reasonably addressed; however, the Geotechnical Engineer’s needs are largely overlooked. This document is only suited when providing the “prescriptive” option for a RFP.

A Different Approach A different approach would be to issue an RFP that states your desired results and contains sufficient information for the Geotechnical Engineer to provide a proper Geotechnical Report that addresses the needs of the Structural

Engineer, eliminating the need for extensive follow-up correspondence.

The Solution: Team Effort How do you then satisfy both the Geotechnical Engineer’s and the Structural Engineer’s needs?

About 10 years ago, a group of Michigan Structural and Geotechnical Engineers formed a group to discuss this concern. The bottom line of these discussions: a good Geotechnical Report is a team effort between the two disciplines. The group’s efforts resulted in a Master RFP for Geotechnical Investigation and Report.

It contains two major points: 1) The Structural Engineer is required to: a) furnish specific information about the proposed structure and its location, and b) describe the specific results that are desired.

2) The Geotechnical Engineer is required to address the list of specifics requested in the RFP. The intent is for the Structural Engineer to edit and “fill in the blanks” contained in the Master RFP; the edited version is then supplied to the Geotechnical Engineer. The Master RFP is available for your review at: www.seami.org/geotechnical%20RFP.html.

The Master RFP contains many commentary items aimed at assisting a person new to the format in developing a site- and building-specific RFP.

Structural PracticeS practical knowledge beyond the textbook

The RFP for the Geotechnical Report

Issuing the RFP How and when then does the RFP get issued?

The “How”: You may issue it in conjunction with the Architects terms and conditions. Another method is to use it as an attachment to AIA G-602.

The “When” : We suggest you hold up issuing the RFP until the results of the Schematic estimate are complete. Note, this does not mean just the structural schematic; it means the other disciplines as well. Why such an extensive requirement? There are often major adjustments to the footprint and the number of stories to meet the Owner’s budget. Alternately, if you have a 50 acre site, and various options of locating the structure are possible, issue a preliminary RFP. Request just the basic info for each option and an initial Seismic Site Classification. If one location has better foundation conditions than others, the potential cost savings should be conveyed to the Architect as input for the final site location. continued on next page.

STRUCTURE magazine

25

Small Effort Yields Big Dividends

By Gerd W. Hartung, P.E., S.E. and Richard O. Anderson, P.E.

Gerd W. Hartung, P.E., S.E. is retired from HarleyEllisDevereaux in Southfield, MI, where he was Principal, Structural Engineering.

He now is a part-time consultant.

He may be contacted at expert.struct@gmail.com.

Richard O. Anderson, P.E., Dist M. ASCE is a Principal Engineer at SOMAT Engineering, Detroit, MI. He may be contacted at roape1@aol.com.

Major Geotechnical and Structural Needs Summary Geotechnical Engineer’s Needs

Why

1. A site plan with topographical information, showing the location of the building and its relationship to other nearby structures, if any a. If the location is not fixed, an approximate envelope for the locations should be considered.

A. The Geotechnical Engineer usually has subsurface maps that show the general composition of the soils, or first-hand knowledge of the geotechnical conditions on this site or nearby sites.

B. If the proposed building is located near existing facilities, foundation sizes and types may have to be changed in order to avoid conflicting with or overstressing the existing foundation system.

C. If the location is not fixed and an envelope is provided, the Geotechnical Engineer will evaluate the entire envelope.

2. Information regarding the ownership of the property

A. If the property is owned by anyone other than the client issuing the RFP, this information needs to be conveyed to the Geotechnical Engineer in order to coordinate proper site access authorization.

3. A preliminary slab on grade plan, with preliminary column A. The slab on grade elevation will provide the Geotechnical Engineer with information regarding additional surcharges on the existing grades if the slab-on-grade is higher locations and preliminary column loads, as well as the than the existing contours. elevation of the slab-on grade a. Also to be shown, if generally known, the approximate B. The column location is important for the “pressure bulb” considerations if there are closely spaced columns that are variations to the general planning grid. locations for the lateral support system, and its vertical C. The location and type of lateral load support system is required if uplift loads are to and lateral loads be considered. A maximum settlement recommendation for a braced frame may be i. SE’s note: The extensive use of RISA or similar 3-D more stringent than that of a moment frame. (As an SE, you would not want too engineering programs makes this a relatively easy effort. much base rotation in a brace.)

4. Use of proposed structure and that of the adjacent facilities

A. A hospital with extensive brain surgery or eye-surgery activities would be negatively affected if “driven steel piles” is the recommend foundation system for any nearby construction, be it an addition or a stand-alone structure.

5. Type of frame: concrete, steel, masonry bearing

A. The type of frame matters to a Geotechnical Engineer only as further understanding of the total design.

6. Site/civil considerations that are part of the contract

A. Geotechnical Engineers are usually proficient at recommending pavement types. If this is issued as part of the Geotechnical Report, overall cost savings could be achieved.

B. As an aside, this would require additional coordination between the Structural and Civil disciplines.

7. Corrosion and grounding considerations that are part of the contract

A. Similar to site/civil considerations

8. Any unusual total or differential settlement constraints, structure loading conditions, or site specific physical constraints that would affect the type of foundation system recommended

A. If there are unusual site specific or building specific constraints, then the Geotechnical Engineer should be made aware so that the drilling and sampling program can be tailored to the constraints and these issues can be addressed in the report.

Structural Engineer’s Needs

Why

1. Clear and unambiguous recommendations for the foundation system, whether spread footings, deep foundations, or some other proprietary system

A. Some Geotechnical Reports contain so many “however” statements that the SE has only a vague idea what the recommended foundation system should be.

2. Settlement recommendations

A. Self-explanatory

3. Soil lateral load capacities

A. Generally used at brace and shear wall foundations and in certain instances, depending on the slab-on-grade characteristics, where the building backfill is not equal or not nearly equal on opposite sides; this capacity consists of two (2) distinct values: 1. The lateral resistance of the soil 2. The coefficient of sliding for a specific type of soil B. If a deep foundation system is recommended, the design-software generally requires the soil lateral capabilities for the input.

C. As an aside, these values may also come in handy when the Contractor/CM requests permission to backfill against the basement walls prior to placing the slab-on-grade. SEs note: this should be done on the basis of “additional service”, and not a “freebie”.

4. Lateral loads imposed by the soil onto the building

A. Generally relating to the basement lateral pressure, although loading docks and retaining walls may require this same information

5. Seismic Site Classification a. Evaluate potential for a more detail study to obtain a more accurate classification

A. The SE needs this value to calculate the Seismic Design Category (SDC).

B. A higher SDC will not just add cost to the structure, it could result in added cost for the other disciplines.

STRUCTURE magazine

26

March 2013

6. Groundwater conditions

A. If there is a high design-groundwater table, this could impact the design of any below-grade portions of the structure.

7. Slab-on-grade recommendations

A. There may be unsuitable soils that will need to be undercut.

B. Other sub-grade preparations may need to be considered.

8. Excavation slope stability

A. Provides information to the contractor determining when and where to use temporary shoring and indicates if open-cut-excavation would potentially undermine existing utilities, driveways or other site fixtures

9. Suitability of excavated materials for site fill

A. Generally, excavated materials are used elsewhere on the site; compaction requirements should be provided for possible use under slabs-on-grade, parking areas or lawns.

10. Anticipated construction problems

A. Draws attention to unusual soil, groundwater, or rock conditions that could impact the design and/or construction of the structure

Review of the Proposal(s) for Geotechnical Work Issuing the RFP should not be the end of the SE’s involvement. The proposal needs to be reviewed to verify that it meets the intent of the RFP. If you requested specific line items, are they there? Is the time-frame for the issue of the report in line with your requirements? Is the number of borings reasonable, and not purposely “low-balled” to have a “cheap” report?

For the case where the RFP was sent to more than a single entity, the SE is generally expected to make a recommendation to the Owner for the selection of the firm to do the work.

The low cost firm may not be the one you feel provides the “best bang for the buck”.

Convey your reasons for your recommendation to the Architect/Owner as appropriate.

Geotechnical Engineer. This item lets the Geotechnical Engineer confirm that his or her recommendations were properly interpreted.

Other Reviews

Summary

The author of the RFP may want to include the following as part of the basic scope: 1) Review of the final draft of the Geotechnical Report by the Structural Engineer. Note: this is not to embellish the RFP, just to make sure that the bases are covered.

2) Review of foundation plans and related specifications by the

A well-scoped RFP will result in a report that minimizes questions and results in unambiguous recommendations. The time spent preparing the RFP is more than made up with fewer questions to the Geotechnical Engineer on the contents of the report. Your comments/ suggestions are encouraged.▪

ADVERTISEMENT - For Advertiser Information, visit www.STRUCTUREmag.org

STRUCTURE magazine

27

March 2013

Technology information and updates on the impact of technology on structural engineering

S

tructural engineering design firms looking for opportunities to increase revenue, which today should include most everybody, should consider looking to our close neighbors on the construction side of the industry for inspiration. Based on the construction business model and the ever-increasing interoperability of today’s Building Information Modeling (BIM) software, today’s structural engineering workflows can be reshaped to take advantage of technology to improve project returns.

Consider the current workflow. Structural engineering firms currently leverage BIM technology to model, analyze and document their designs.

These designs are then passed on to the fabricators via 2D construction documents. The project is then remodeled by the fabricator who adds the connections, possibly designed by a third party engineer, to the fabrication model. From this fabrication model, shop drawings are then created and returned to the Engineer of Record (EOR) for approval. Once approved, fabrication can begin.

This workflow is severely outdated, given that current technologies provide the tools to enable EORs to leverage their BIM models to add structural steel connections, analyze them and detail these connections into a set of shop drawings. With this functionality at the ready, how can your structural engineering firm become a “Single-Source” EOR of the future, generating the extra income from the increased scope of work?

Let’s explore these evolving work practices and how your firm can fit into this new reality.

Bringing It All In-House The Future of “Single-Source” Structural Engineering

By Joshua Gionfriddo, E.I.T.

Joshua Gionfriddo, E.I.T. is a structural engineer and consultant for Microdesk, Inc. He specializes in providing BIM training, implementation, and consulting services to structural engineering clients. Josh can be reached at jgionfriddo@microdesk.com.

Staying Competitive in Today’s Market If EORs can begin to more effectively leverage all available BIM resources, they can put themselves in the advantageous position of being able offer the lowest cost while maximizing the firm’s profits due to the interoperability of BIM software and the collaboration available within. For example, by managing tasks such as structural detailing, any changes to designs could be made all at once, significantly minimizing the cost of those changes, an efficiency not achievable when this process is outsourced.

Thornton Tomasetti (TT) is one well-known engineering firm that offers these Single-Source construction services. When asked to describe the efficiencies that being a Single-Source EOR provides to their clients, Josh Bradshaw, Tekla BIM Manager for TT offered this: “Using the internally developed interoperability, we are able translate our models directly to Tekla Structures.

Our Construction Support Services team can deliver a Tekla model of base geometry for mill

28 March 2013

order, include a few conceptual connections, or include all connections, and even produce the fabrication drawings. The connection design team can leverage the BIM to study complex conditions and to communicate directly to the detailing team. This level of collaboration between the design and detailing phases allows those two tasks in the construction timeline to overlap, decreasing the overall schedule of the project.”

The Realities of This New Contractual Relationship Currently, any added efficiencies that structural engineers bring to a project via BIM are not being reflected in the structural engineering firm’s bottom line. In some cases it is just the opposite, as owners increasingly shrink deadlines and fight for reduced fees, falsely believing that BIM saves the designer time. The time savings BIM affords is manifested mostly on the construction side of the project. Although it’s the owners that need to understand this, it’s the design community’s job to educate them.

There are groups of architects and groups of engineers but there is no all-encompassing group of owners, so this education must take place on a project-by-project basis. Designers must show owners how they would benefit from this new level of coordination. Not only would the project costs be reduced due to elimination of duplication of design work but, by extending the benefits of BIM to the construction side of the project, substantial savings can be realized. A steel connection that must be modified in the field costs 10 to 20 times the original shop fabricated version. Eliminating the need for these types of costly field repairs offers tremendous cost saving opportunities to all parties. Contractual relationships change for Single-Source firms. When this process is applied to typical design-bid-build projects the structural engineer would have two contracts, one with the owner/architect for traditional design services and one with the construction manager/fabricator for the connection design and detailing services. This dual services contract can be executed directly with the owner or contractor for a design-build project, making this the optimal project type for Single-Source firms.

Where This New Workflow is Most Efficient A Single-Source workflow alleviates many of the traditional project pain points, reducing RFIs, eliminating third party shop drawing review and optimizing connection design. The interoperability of design and detailing software allows for a seamless transition from design model to fabrication model to the built structure. When asked to describe their workflow advantages, Ken Murphy, BIM Director

Design, Analyze and Detail, above are screen images from Autodesk Building Design Suite showing a single model in all three phases.

for TT offered this: “We explore multiple design and analysis iterations using internally developed interoperability, design computation and automation. This allows extremely fast generation of models not only in analysis, but also on the BIM side. By using many different platforms in our project delivery, we can choose the best tools for the complex jobs and maximize not only our efficiency but also the quality of the deliverable BIM.”

Getting the Tools to Get Started

STRUCTURE magazine

ADVERTISEMENT–For Advertiser Information, visit www.STRUCTUREmag.org

Firms that wish to take on this increased work scope will have some hurdles to overcome.

Additional training will be needed to get a design staff BIM-ready. Firms too often don’t take this seriously, and for years projects using new technology can flounder because a proper understanding of the technology was never had. The level of accuracy in the design model will need to be detail ready, but BIM software is inherently accurate. With proper use, BIM software wants to be accurate. However, improper modeling techniques can lead to accuracy errors, so additional training of traditional CAD staff will be necessary when implementing this Single-Source workflow. Design staff must have an understanding, before a project kicks off, that this BIM model will be used for fabrication so they can model with appropriate accuracy. Additionally, as detailing work is best done by specialists, additional staff may need to be hired.

However, these workers should be skilled and ready to contribute to the organization on day one. Another of the roadblocks to implementing Single-Source engineering for medium and small-sized firms has been the prohibitive upfront cost of detailing software packages such as Tekla or SDS/2. As noted by Josh from TT, these traditional detailing software packages don’t work seamlessly with BIM software. But as

more software providers enhance their offerings with interoperable suites of products, such as Autodesk’s Building Design Suite, the barrier to the average firm is being eroded. Now, within a single software purchase, you get all the tools to design, analyze and document full building design. Structural engineering firms that begin to integrate these tools and adopt a SingleSource workflow will be well positioned to differentiate themselves from the competition and effectively capture more business.

Impediments for Engineers to take on this scope of work include: 1) Real or perceived increase in liability.

2) Added training.

3) Added staff.

4) Added interoperability systems are needed.

At this point in time, the average engineering firm is still trying to figure out how to implement BIM into their practice without incurring too much additional cost. BIM software is just not yet up to the level of versatility and ease of use of CAD software, so that most firms still incur more cost in developing drawings in BIM. So, the move to include detailing is likely yet a ways off.

Moving forward, it needs to be determined at the very start of the engagement if the model will be used for follow-on detailing in order to ensure that the proper level of accuracy is used.

Providing the accuracy level in the initial engineers’ BIM model required for shop detailing will take some additional effort.

Engineering CAD drawings, and to some degree current BIM practices, do not require the level of dimensional accuracy needed to get down to the 1/16 inch accuracy needed for detailing.

Adding the shop drawing detailing to the engineer’s scope of work will greatly increase the revenue to be gained by the engineer, but it should be an overall savings to the owner by elimination of work duplication.▪

29

March 2013

GT STRUDL Structural Analysis & Design Software

7

NEW RELEASE - VERSION 32

The Best Choice for Infrastructure & Nuclear Base Plate Module

Georgia Tech - CASE Center www.gtstrudl.gatech.edu casec@ce.gatech.edu 404-894-2260

In 2012, three members of NCSEA Member Organizations under the age of 35 received scholarships to attend the Annual Conference in Saint Louis National Council of Structural Engineers Associations for writing essays on the benefits of Young Member Groups (YMGs) within Structural Engineers Associations (SEAs). Heather Anesta’s submission appeared in the NCSEA News portion of the April 2012 issue of STRUCTURE magazine. The two others are included here, along with a piece written by a more senior professional to provide an additional point of view.

GINEERS

O NS

STRUCTU

OCIATI

NATIONAL

ASS

RAL

EN

COUNCIL

NCSEA

Professional issues issues affecting the structural engineering profession

The Benefits of a Young Member Group

By Dallin Pedersen, P.E.

S

EAs are prolific throughout the United States. Organized by structural engineers who care about their profession and want to improve and elevate those who practice it, SEAs meet regularly to discuss current advancements, network, and provide continuing education for their members. The organization of most SEAs caters primarily to experienced, practicing design professionals; however, a young engineer or student can sometimes feel left out. Young engineers are getting valuable design experience in their offices, but might feel intimidated when it comes to asking questions of their more experienced colleagues. The purpose of this essay is to describe how a Young Member Group (YMG) within an SEA can benefit both the young engineer and the profession in the areas of education, licensing, and networking.

Regarding education, young engineers typically come into the profession with a deep desire to learn. In college, their learning was mostly limited to analysis and design of typically straight-forward, textbook examples. Once employed, they discover that the world of design is extremely different from what they experienced in school.

Code requirements, consultant coordination, construction administration, and other aspects of practice are thrust into their laps with some guidance and a directive to “do your best” from their employers. The YMG is intended to provide a risk-free environment for young engineers to collaborate, discuss problems and learn from the situations that they and their colleagues have faced. The YMG gives them the opportunity to share their successes and lessons learned in a context that is open and inviting.

As young engineers learn from each other, they can discuss what was missed during a peer review, how to handle a certain code provision, or what structural systems they have employed. The YMG can also be place where more experienced engineers from within the SEA can teach these young minds. The pressure of appearing as competent as possible will lessen as a forum is established where questions and respect are first and foremost.

As young engineers collaborate and edify each other through these discussions, quality of design,

efficiency in analysis and responsiveness in coordination will increase throughout the profession.

YMGs can also aid young engineers with their first post-graduate milestone, which is attaining licensure. When studying for exams, synergy between engineers in the YMG can lead to higher exam passing rates. As young engineers both learn and remember the concepts required by the exams, collaboration can increase the likelihood of success. By helping with structured study sessions, engineers can study for the PE and SE exams while still keeping their busy professional and personal lives in balance.

Finally, young engineers are constantly surrounded by new faces, which may consist of professionals within the SEA, consultants from other engineering fields, architects, and contractors. The benefit of networking is that the vibrant talent of young engineers can be diffused into the professional community to enhance the influence of the SEA. Interaction among young engineers within construction companies, detailing shops, and various consulting firms will have a positive effect on the SEA by broadening its base of knowledge, and may even strengthen the local economy by working out potential issues and exploring better ways to design and construct.

The sooner an engineer becomes involved in an SEA, the better. Joining a YMG is the initial and best path into professional structural engineering. When an SEA has a YMG, the SEA can reach out to the young engineers and find ways for them to get involved and assist in their own development. By helping others, we all can help ourselves.

Three Perspectives on Encouraging Younger Engineers

Dallin Pedersen, P.E. is a project manager with BHB Consulting Engineers in Salt Lake City, Utah. He can be reached at dallin.pedersen@bhbengineers.com.

STRUCTURE magazine

continued on next page

31

By Dallin Pedersen, P.E., Emily Guglielmo, P.E., C.E. and Timothy M. Gilbert, P.E., S.E.

How Can Young Member Groups Benefit Both Young Engineers and the Entire Profession?

By Emily Guglielmo, P.E., C.E.

S

tructural engineering is at a critical crossroad. Focused and visionary leadership from young engineers is vitally needed to address our current professional challenges, including a worldwide recession, pressure for sustainability and green building designs, and the potential for future outsourcing of work. Further complicating the situation for young engineers is unpreparedness due to a lack of practical experience early in a career, combined with increasing code complexity. In addition, structural engineering falls short with respect to the gender and ethnic diversity required for a healthy profession, which should reflect the society that we serve, especially considering the vital importance of what we do in the community at large.

Young engineers need sufficient technical training and strong career mentorship to be adept in addressing the previously mentioned challenges. SEAs are in a position to play a major role in enhancing the success of young engineers and the profession as a whole.

Several local SEAs have already established active YMGs, which have provided outstanding value for those who participate in them.

In Northern California, the SEAONC Young Members Forum provides PE mentoring, consistent email updates, and an active working committee. This program has the potential to provide its members with a strong skill set, improving the likelihood of professional success and creating a pipeline of leaders for the profession.

While these local efforts are beneficial, I believe that a national Young Members Committee within NCSEA would offer more universal benefits to young engineers nationwide. This virtual community could offer several benefits for younger engineers.

For example, a secure, universally accessible platform for discussion could be created through an online member’s only forum on the NCSEA website. It could be specifically designated for young engineers and would provide a safe source for dialogue, support, and learning. Another mechanism for encouraging young engineers’ professional development would be to enhance and further focus NCSEA’s technical articles and E-newsletter to include basic tips specifically aimed toward young engineers.

SEA, SEI, and ASCE seminars have proven to be invaluable to my success in

my career. While NCSEA offers content covering numerous key topics, relatively few explicitly focus upon the needs of junior engineers. Focusing on practical aspects of structural design, such as lessons learned from completed projects, reviews of common mistakes and their avoidance, and discussions of techniques for verifying the accuracy of computer analysis and design would be invaluable for younger engineers.

Similarly, offering an online “Frequently Asked Questions” page addressing subjects more relevant for new professionals would result in another key resource.

While today’s professional challenges appear daunting, I view this time as one that offers an excellent opportunity for young engineers. As a valuable investment toward the development of the next generation, Young Members Groups, both locally and nationally, unequivocally benefit young engineers, the profession, and society.

Emily Guglielmo, P.E., C.E. (EGuglielmo@martinmartin.com), is a senior project engineer with Martin/ Martin, Inc. in Larkspur, California.

Encouraging Younger Members

By Timothy M. Gilbert, P.E., S.E.

ADVERTISEMENT - For Advertiser Information, visit www.STRUCTUREmag.org

T

he recent NCSEA Annual Conference provided engaging and exciting learning opportunities for all in attendance. One

Foundation Performance Association

FPA hosts regular events, sponsors the publication of technical papers and research material. The presentations are great for networking and low cost CEU’s. Membership is $96/yr; this can equate to CEU’s as little as $8/CEU. www.foundationperformance.org

of the highlights for me was the energetic and thought-provoking presentation by one of the Young Member Group (YMG) Scholarship Award winners, Heather Anesta. Her obvious passion for structural engineering and persuasive communication show that the future of structural engineering is in good hands.

Before we “pass the torch,” let me offer a challenge to those of us in leadership or supervisory positions. Heather made plain that one of the services that YMGs offer is an opportunity to ask questions without fear of reprisal. I challenge us to help bridge the divide created by that fear.

Let us work to establish environments where young engineers can freely seek the knowledge needed to advance within the profession.

One way in which we can work toward this goal is to build better relationships with

STRUCTURE magazine

32

March 2013

younger staff. Here, there is no substitute for regular one-on-one meetings. Supervisors and project leaders can build a communication bridge by establishing recurring occasions when – this is important – the other person opens the conversation with a topic of his or her choice. Giving the first move to the young engineer helps demonstrate our receptivity to his or her thoughts and helps avoid creating the impression of receiving a lecture. We may choose to follow up with a response or different topic later in the meeting.

Our tight project schedules and increasing workload might make this concept appear to be a luxury. A different point of view is worth considering; those schedules and workloads make this kind of process even more imperative. Incomplete and ineffective communication can obstruct or even derail our objectives. We can use our time

B U C K L I N G

B R A C E S

Santa Clara Stadium future home of the

San Francisco 49ers

We have the tools you need to complete your BRBF project: ✔ Bolted, Pinned, and Welded Connections— Fully Qualified and Exceeding AISC 341 Requirements ✔ Real-Time Engineering Assistance ✔ Non-linear Modelling Design Guides (SAP, RAM, ETABS, Perform 3D, etc.) ✔ Maximum QA/QC and Scheduling Control ✔ Integration with RAM Structural System and REVIT ✔ New! “Near Fault Effect” Testing

Timothy M. Gilbert, P.E., S.E. (TGilbert.PE@gmail.com), is a Principal Quality Engineer with Louis Perry & Associates in Wadsworth, Ohio.

He is also a Director and the Licensure Committee chair for the Structural Engineers Association of Ohio (SEAoO).

WWW.COREBRACE.COM

STRUCTURE magazine

33

March 2013

801.280.0701

ADVERTISEMENT - For Advertiser Information, visit www.STRUCTUREmag.org

in these meetings to make sure that our previous messages have been properly received and understood by the listener.

On today’s complex, fast-paced projects, subject to quick changes, a robust communication bridge is vital. It can help minimize errors and rework, improve employee and client satisfaction, and – best of all – let us learn from the bright young engineers in our offices.

Along with regular meetings, frequent feedback about specific items can help develop more effective practices. The term “feedback” is often used to describe criticism, but the intent here is different.

Provide comments about particular items and their effects. Positive feedback can produce great results, and negative feedback delivered respectfully offers guidance. Here are two examples: • “The sketches that you provided in the connection calculations were very helpful in checking your work. Please keep it up!”

• “The equations that you used in the shear wall calculations did not include a reference to the code section. Could you please be sure to add that next time?”

Frequent feedback about small issues can help avoid big problems. One important thing to consider prior to delivering feedback: take a few moments to reflect on your own career and the mistakes that you yourself have made in similar situations.

This can help us say what needs to be said with kindness and humility, which will make it more likely to be heard.

It is up to us to help today’s young engineers become tomorrow’s outstanding engineers. After all, they are the ones who will design our grandchildren’s schools and the bridges over which they will travel.

R E S T R A I N E D

Structural teSting issues and advances related to structural testing

O

wners and designers may find themselves confronted with the task of deciding what to do with an existing masonry building, particularly if there will be a change of use or modifications to the structural system. Part of that decision should include determination of whether the structural system is adequate in its current condition for the building’s intended use, whether minor or extensive repair and retrofit measures are required, or whether the building has deteriorated to a state that it is beyond its usable life. Nondestructive and minimally invasive diagnostic techniques play a vital role in determining properties of existing masonry construction without causing excessive disturbance or disruption to the building fabric.

This article discusses the different methods available for identifying masonry distress conditions and evaluating engineering properties such as strength and stiffness.

Evaluating Existing Masonry Construction Nondestructive and In -Situ Methods

By Andrew Geister, P.E.

Andrew Geister, P.E. has been involved in masonry nondestructive, in-situ, and laboratory material testing while working for AtkinsonNoland & Associates, Inc. in Boulder, Colorado. He is also a member of The Masonry Society’s Existing Masonry Committee and Design Practices Committee.

Andrew can be reached at ageister@ana-usa.com.

Material Properties

The masonry material properties needed by the engineer will ultimately depend on the role of masonry in the overall structural system, but may include compressive strength, shear strength, presence and extent of voids, existence and condition of reinforcing, and even moisture resistance.

The use of destructive techniques may be undesirable due to the cost, damage and potential structural instability resulting from creating large openings or removal of several material samples.

Fortunately, many nondestructive and in-situ methods exist, several of which have standardized procedures to determine necessary material properties without causing undue damage to the structure.

The keys to establishing a successful masonry testing program include determining which material properties are critical to the building’s intended use, as well as selecting an appropriate number of tests and test locations. For reinforced masonry, quantifying the presence of voids in grout, and location of reinforcing are likely to be some of the most important properties. For unreinforced masonry, particularly in historic construction, determination of compressive strength, elastic modulus, and shear strength is especially important in order to take advantage of these inherent material properties in design.

In situations where variable construction or workmanship are encountered or suspected, additional testing can also help determine appropriate design values for different construction phases or parts of the building. For nonstructural masonry such as veneers, the focus will more likely be

34 March 2013

Figure 1: Using a fiber optic borescope inserted into a drilled hole in a mortar joint to view the inside of a concrete masonry lintel.

on connections to the structural system, moisture management, and energy issues rather than strength properties.

Nondestructive Techniques Voids and Reinforcing When investigating how solidly an existing masonry wall was built, simply tapping with a sounding hammer may be sufficient to determine if CMU cells are grouted or empty. For smaller voids and cracks in thicker, multi-wythe walls, more sophisticated techniques and equipment may be needed. Ultrasonic methods, such as pulse velocity which measures the transit time of stress waves between transducers, or impact-echo which measures the stress wave reflections from discontinuities in the structure, are both good tools for assessing the extent of internal cracks and voids.

These types of irregularities can also be observed visually through the use of a fiber optic borescope inserted into an existing opening or small diameter drilled hole within a mortar joint (Figures 1 and 2). This method is also useful in cavity wall construction for observing veneer ties or excess mortar inside the wall cavity. Somewhat larger scale voids can be detected through the use of Surface Penetrating Radar (SPR) which locates material differences indicated by reflected microwave energy, and Infrared Thermography (IRT)

Figure 2: Borescope view of voided grout space around a reinforcing bar.

throughout the structure. Half-cell testing, however, has been used successfully to determine the potential for metal corrosion in reinforced masonry at locations that are electrically connected to the exposed bar, such as along a single vertical reinforced cell or along a bond beam.

Masonry Strength and Stiffness An estimate of masonry compressive strength and elastic modulus is determined through the use of Flatjacks following the standard test method of ASTM C1197. Flatjacks are

thin hydraulic bladders inserted into slots cut in masonry bed joints, and pressurized to perform an in-situ compressive strength test while monitoring the surface strain of the masonry between Flatjacks to generate a stress-strain curve (Figure 3). Although this method requires sawcutting two slots in the mortar joints to insert the Flatjacks, it is much less destructive than the removal of masonry prisms, which may be damaged during sampling or transport.

If the current stress state of the masonry is desired at a particular location, the single

Figure 3: Masonry deformability test by the Flatjack method to estimate masonry compressive strength and elastic modulus.

Both Flatjacks are pressurized while monitoring surface strain to generate an in-place stress-strain curve.

ADVERTISEMENT - For Advertiser Information, visit www.STRUCTUREmag.org

which is capable of detecting temperature differences between the solid masonry materials and voided air spaces.

The existence of metal reinforcing bars, steel sections, or even pipes and conduit may be detected using SPR, relying on the highly reflective nature of metal objects to the transmitted radar energy. Other types of metal-detection devices such as a pachometer are also useful for locating veneer ties, joint reinforcing, and reinforcing bars that are located near the wall surface. Once the reinforcing is located, information about its size or quality may be desired. If a small opening exists or can be made to expose a portion of the metal reinforcing, its thickness can be measured using an ultrasonic thickness gauge without having to uncover the entire bar to take a physical measurement. The device transmits a sound signal into the exposed surface of the metal, and measures the amount of time required for the sound to travel through the material and its echo to reflect back to the surface. Half-cell testing measures the potential for corrosion of metal reinforcing by first connecting a wire from the device to a small exposed portion of reinforcing, and then surface measurements are made throughout the structure. This method has been used more commonly in reinforced concrete structures containing mats of reinforcing bars that are in contact or close proximity with one another, and thus has been able to provide good electrical continuity

Star Seismic BRBs land bigger projects It’s no fish story. Contact Star Seismic to see how we can help you land your next trophy project.

STRUCTURE magazine

Call: 435.940.9222

www.starseismic.net

35

March 2013

Figure 4: Infrared thermograhpy image showing areas of rising damp and path of moisture travel.

Flatjack method of ASTM C1196 provides a means to measure this property. First, the stress is relieved by cutting a horizontal slot in the bed joint, which also causes the masonry above to deform slightly. The Flatjack is then inserted and pressurized, and the pressure is measured as the masonry above is restored to its original position.

Similarly, masonry mortar joint shear strength may be measured using the standard test method of ASTM C1531, which utilizes a single specially sized Flatjack, also known as a “Shearjack,” to fit within a head joint, which is pressurized until it moves the adjacent brick unit sideways into the opposite, previously opened head joint.

Mortar Qualities If there are concerns about the quality or uniformity of the mortar used in the existing construction, mortar quality and consistency throughout the building may be evaluated and compared using a rebound hammer, which measures the amount of rebound of a pendulum weight after striking the mortar surface, similar to the use of a Schmidt hammer device used for testing concrete surface hardness. In addition to surface hardness, knowledge of the mortar characteristics deeper inside the wall may be needed, such as in situations where past repairs or repointing have covered the original mortar with a different type of material. Resistance drilling techniques have been reported to produce good correlation with mortar compressive strength values, and only require small holes drilled in existing mortar joints.

deterioration can occur more quickly if masonry remains saturated. Keep in mind, when investigating masonry moisture issues, that both the source of the moisture and the water penetration properties of the masonry are important. When weather conditions permit, IRT is useful for locating moisture paths and damp areas (Figure 4). Many types of electric capacitance-based moisture meters and resistance-based probes are available for detection of wet areas and are useful for tracing the moisture path to its source. The rate of moisture penetration through masonry walls is determined using the standard test method of ASTM C1601. The standard test chamber mounted to the masonry surface applies water and pressure, creating conditions that simulate wind-driven rain (Figure 5). The rate of water loss from the chamber into the masonry is measured, and is used to determine its water penetration resistance.

Visual observations of the opposite wall face during the test can also give useful information about the path the moisture takes as it travels through the wall. A very fast and simple method for measuring water movement through a masonry surface is the water absorption tube test given by RILEM method II.4. RILEM (English translation from French: International Union of Laboratories and Experts in Construction Materials, Systems, and Structures) is an international technical organization which develops standards for testing materials and structures, similar to ASTM in the United States. Different tube sizes are available, but the configuration consists of a circular opening perpendicular to a vertical graduated tube. The opening is attached to the masonry surface and the graduated tube portion of the tube is filled

Figure 5: Moisture penetration testing for masonry walls using ASTM C1601 water chamber.

with water, resulting in a pressure head being applied to the masonry surface. This type of testing is attractive because many tests can be performed quickly, and is useful for getting an impression of masonry absorption, or for comparing water repellent treatments.

Quality & Performance Quality Control A successful construction or repair project depends on the quality of work performed being as good as it was designed and specified to be. Nondestructive methods such as SPR and IRT are especially useful to determine the effectiveness of repairs such as rebuilding or injection, especially when a “before and after” comparison can be made with the results. Metal detection methods are also helpful for confirming the placement of retrofit anchors or veneer ties without visual observation. The costs associated with these methods

Material Characteristics

Test Method

Compressive strength, elastic modulus

Flatjack (ASTM C1197)

In-situ stress

Flatjack (ASTM C1196)

Shear strength

Flatjack “Shearjack” (ASTM C1531)

Voids

Surface Penetrating Radar, Infrared Thermography, Borescope, Sounding, Pulse Velocity

Moisture Management

Cracks

Impact echo, Pulse velocity (ASTM C597)

Moisture problems can be one of the biggest threats to both structural masonry and veneer systems. Although masonry is generally a very durable material, exposure to excessive amounts of moisture can lead to unsightly efflorescence, plant growth, and premature deterioration. In climates that produce freezing temperatures, especially those with many cycles of freezing and thawing,

Reinforcing and metal objects

Surface Penetrating Radar, Pachometer

Reinforcing condition

Borescope, Ultrasonic thickness gauge, Half-cell potential (ASTM C876)

Mortar consistency & quality

Rebound hammer, Resistance drill

Moisture penetration

Spray chamber (ASTM C1601), IRT, Water tube (RILEM II.4)

Crack width & building movement

Structural monitoring

STRUCTURE magazine

36

March 2013

6). During construction, monitoring is useful to determine if the ongoing activity is causing additional building distress or movement. The activity does not necessarily need to originate from your site to affect your structure, either.

An adjacent excavation or heavy equipment can affect your building as well.

After repairs, strengthening, or stabilization work have been completed, a long term structural monitoring program will result in valuable data that will aid in diagnosing future distress, aid in detecting potential problems before they become serious and more expensive to fix and, finally, ease concerns about long term structural performance.

Figure 6: Vibrating wire crack monitors used for long-term structural movement monitoring.

are likely to be lower than providing full-time inspections, or opening completed repairs for observation and repeating the repair work.

Structural Monitoring A good monitoring program can provide peace of mind before, during, and after repairs are conducted. Before deciding which repairs are necessary, structural monitoring can help determine if cracks are active or dormant, and if the building is moving, whether the

movement is due to natural weather cycles or something more serious. Monitoring systems that operate on vibrating wire technology feature a central datalogger connected to sensors that are capable of measuring crack width, tilt angle, surface strain, and temperature. The system itself requires only a low power input, so extended longevity is possible with little maintenance. These monitoring systems can be installed using adhesives or small anchors, so the impact to the structure is minimal (Figure ADVERTISEMENT - For Advertiser Information, visit www.STRUCTUREmag.org

STRUCTURE magazine

37

March 2013

Conclusions A variety of nondestructive and in-situ methods exist to determine material properties and to diagnose problems in existing masonry structures without the need for sample removal. The information gained from a testing program that is well-planned and performed correctly, with results interpreted by experienced professionals, can reduce costly repairs to the concentrated areas where they are needed, and can provide design engineers with confidence about the materials they are working with on any given project.▪

Crossed Arches Pipe Bridge

By Wayne A. Bamossy, P.E., M. ASCE, Jennifer A. Barrick, P.E. and William W. Lai, P.E. Spillgates of the Hansen Dam, source of the Tujunga Channel, upstream of the crossed arches pipe bridge.

M

ies van der Rohe’s famous maxim, “Less is more,” clearly applies to the pipe bridge recently built across the Tujunga Channel in the Lake View Terrace area of Los Angeles to supply recycled water to the Hansen Dam Municipal Golf Course. Overall simplicity and sparing use of material contribute to what strikes many as an elegant appearance.

The bridge is part of the Hansen Dam Golf Course Water Recycling Project of the Los Angeles Department of Water and Power (LADWP).

The Hansen Dam Municipal Golf Course will soon join several other golf courses, cemeteries, parks, and nurseries in the LADWP service area that use recycled water for irrigation of large areas of turf or other landscaping. The view of the pipe and bridge also illustrates why LADWP staff often refer to recycled water projects as “purple pipe projects”.

View of the completed crossed arches pipe bridge.

• shortest possible construction duration • strong preference that no construction equipment enter the channel • requirement for twelve foot vertical clearance to the channel The Hansen Dam Municipal Golf Course is on USACE-owned land leased to the City of Los Angeles Department of Recreation and Parks. Golf course management requested a low profile for the bridge and pipeline. The design also was shaped by the LADWP Water Distribution Division’s desire for low maintenance and long Bridge Design service life of the bridge and pipeline.

Owned by the United States Army Corps of Engineers (USACE), Bridge designer William W. Lai, P.E., of LADWP’s Civil & Structural the Tujunga Channel conveys storm water out of the Hansen Flood Design Group, came up with the novel concept of crossed arches after Control Basin to nearby spreading grounds that recharge the San wrestling with the problem of how to provide resistance to lateral Fernando Groundwater Basin or on further to the Los Angeles River. loads, including seismic. Instead of inserting braces between the arches, The Los Angeles County Flood Control Districts (LACFCD) also crossing the arches provided an efficient way to resist lateral forces. regulate work within the channel right-of-way. These two agencies The use of arches allowed the design of drilled pier foundations that established a number of design goals and requirements for the pipe fit within the narrow right-of-way available. and bridge.

The decision to use pipe for the arches stemmed from a desire • easement for the pipe and bridge as narrow as possible to use type 316 stainless steel throughout the bridge structure to • minimal surcharge to the channel walls from the prevent corrosion. The number of structural shapes available in bridge footings stainless steel is limited, but pipe is readily available. Pipe is also more easily bent to radius compared to some other structural shapes.

The Tujunga Channel is 60 feet wide at the bridge crossing. The bridge span is about 82 feet. The bridge carries a 128-foot length of epoxy-coated 20-inch diameter welded steel pipe which weighs about 28 kips when filled with recycled water. Concrete thrust blocks are provided at each end of the water pipe where it bends down 45 degrees to join the buried ductile iron pipeline. The geometric layout of the bridge arches was calculated using analytical geometry formulae in an Excel spreadsheet. Stress analysis was performed with RISA 3D software. Stress levels in the stainless steel were limited to about 60 percent of the values allowed for carbon steel. The governing load was full dead load, Three bridges crossing the Tujunga Channel: golf cart bridge, crossed arches pipe bridge, and rubber dam which produced mostly compressive forces maintenance bridge. Red and white stacks in background are at Valley Generating Station, site of the with some bending. None of the structural recycled water Hansen Tank and Pumping Station.

STRUCTURE magazine

38

March 2013

Bridge Fabrication All fabrication, except rolling the pipe arches to radius, was by the LADWP’s Structural Steel Shop. The 10-inch diameter pipes were rolled to a radius of 86 feet by Marine Valve and Supply Co. of Whittier, California. The bridge, including the chairs, was completely assembled and welded in the shop, except for the mid-span welds.

The shop designed and fabricated temporary supports and braces to keep the bridge arches properly positioned, and LADWP surveyors verified that the alignment was correct.

American 7150 Mobile Crane hoists completely assembled crossed arches pipe bridge into position.

capacity of the welded steel water pipe was considered in design; all loads were assumed to be carried by the arches. Seismic forces induced cyclic load reversal resulting in tension and compression; torsion and bending stresses were minor.

The crossed arches were designed from 10-inch diameter pipe with full penetration butt welds and pinned end connections. Pin-like connections were also designed for the two crossing points. The two connecting structures from the arches to the recycled water pipe, dubbed “the chairs”, each have four legs supporting half-cylinder pipe seats with clamp straps over the top of the pipe. Each leg is an H-shape with 6-inch flanges and a web tapering from 14¼ inches to 3½ inches. The chairs were fabricated by cutting, rolling, and then welding ¼-inch plate. The chair legs are tapered from their bases on the arches to the seats for the water pipe, and the weak axis of the section follows a curved path. The chair legs see moment at their bases and axial force along their length. The seats are lined with neoprene to help prevent galvanic corrosion between the water pipe and the chairs, and also to shield the water pipe from excessive vibration and contact stress.

The two chairs and two end thrust blocks divide the water pipe into spans of approximately 37 feet, 54 feet, and 37 feet. The total bridge steel weight is about 12 kips. The design was modeled and turned into drawings using AutoDesk REVIT Structure software. This approach worked so well that shop drawings were not necessary and all model dimensions were within ⅛ inch of the drawing dimensions.

Yousef A. Gobran, P.E., of LADWP’s Geotechnical Engineering Group, designed four reinforced concrete drilled pier foundations topped with rectangular pile caps sloped at a 45 degree angle.

Each drilled pier is 36 inches in diameter and 21 feet deep, and resists the applied loads by skin friction. The out-to-out width of the bridge and foundations is only ten feet. Jianping Hu, Ph.D., P.E., G.E., also of the Geotechnical Engineering Group, used Sigma/W 2004 software to provide the USACE with a finite element method soil stress analysis to demonstrate that forces transmitted to the walls of the Tujunga Channel from the piers were within acceptable limits.

Bridge Construction LADWP’s Integrated Support Services Division (ISS) built the foundations, erected the bridge, and installed the recycled water pipe and thrust blocks. Each arch was trucked to the site in two pieces. They were then attached to the same temporary supports and braces used during assembly in the shop, surveyed again, and the final center-span welds were made in the field. The completely assembled bridge and the temporary braces were then hoisted into place across the Tujunga Channel with a mobile crane. No equipment entered the channel, as requested by the Regional Water Quality Control Board. The value of prior shop assembly and surveying was confirmed when the bridge was placed and fastened to the foundations on the first attempt. A dual baseplate system was used. One set of baseplates, including leveling nuts, was attached to the anchor bolts on the piers. A second set of baseplates with brackets was pinned to the ends of the arches and then field welded to the first set of baseplates. Once the baseplates were welded, the temporary braces were removed. Then the water pipe was installed on top of the bridge, followed by construction of the reinforced concrete thrust blocks at the ends. continued on next page

Temporary plates, braces, and supports help to fit up the mid-span weld of the crossed arches pipe bridge.

STRUCTURE magazine

39

March 2013

Site preparation and foundation work for the bridge began in March 2011. The pipe bridge superstructure was erected and the recycled water pipe was placed on it in August and September 2011.

Construction of the ductile iron pipeline began in September 2012 by LADWP’s Water Distribution Division. Construction of the pumping station by ISS will begin in March 2013. The initial purpose of the project is to deliver about 500 acre-feet per year of recycled water for irrigation of the Hansen Dam Municipal Golf Course. However, the pipeline and pumping station were sized anticipating customers in addition to the golf course.

Project Credits Project Owner, Engineer, and Constructor: LADWP Fabrication: LADWP Structural Steel Shop Pipe Bending: Marine Valve and Supply Co., Whittier, CA Bridge and Pumping Station Construction: LADWP Integrated Support Services Division Pipeline Construction: LADWP Water Distribution Division

Conclusion Bridge designer, William Lai, believes that the design concept for the small crossed arches pipe bridge over the Tujunga Channel can be scaled up for longer spans and heavier loads. He also believes that the concept could be adapted to loads other than pipe, e.g., a road deck. Until recently, the authors were unaware of other examples of bridges with crossed arches. The December 2012 issue of STRUCTURE magazine features the award-winning Tempe (Arizona) Town Lake Pedestrian Bridge, designed by T.Y. Lin International, which prominently utilizes crossed arches to support the pedestrian deck.▪

Wayne A. Bamossy, P.E., M. ASCE is the Manager of Construction Management Group, Los Angeles Department of Water and Power.

He may be reached at Wayne.Bamossy@Ladwp.com.

Jennifer A. Barrick, P.E. is a Project Manager at the Los Angeles Department of Water and Power. She may be reached at Jennifer.Barrick@Ladwp.com.

William W. Lai, P.E. is a Bridge Design Manager at the Los Angeles Department of Water and Power. He may be reached at William.Lai@Ladwp.com.

ADVERTISEMENT–For Advertiser Information, visit www.STRUCTUREmag.org

Structural Software Designed for Your Success • Easy to Learn and Use • Analyze “Just about Anything!”

• Design: Steel, Wood, Concrete, Aluminum, and Cold-Formed

www.iesweb.com Free 30-Day Trial

IES, Inc. | 519 E Babcock St. Bozeman MT 59715 800-707-0816 | info@iesweb.com

STRUCTURE magazine

40

March 2013

Modeling and Analysis of a Masonry Building on Piling

By Louis Scatena, P.E.

T

his article summarizes the development of a structural model to analyze and design a concrete masonry building that includes a structural steel roof and concrete mat foundation supported on concrete grade beams and drilled concrete piles (caissons). The building (Figure 1 ) will enclose large electrical equipment at a water treatment facility that is near a major seismic fault in northern California. The design was completed by the office of Carollo Engineers in Walnut Creek, California, and the author developed the model and conducted analyses using Bentley Systems STAADPro software.

Design Challenges The project included seismic design considerations that, taken collectively, made modeling the otherwise unimposing Generator Building somewhat unusual, including: 1) Proximity to the San Andreas Fault system in northern California; 2) Large louvered openings in masonry shear walls for air intake and exhaust; 3) Concrete caissons threaded in an unsymmetrical pattern between numerous existing buried utilities; 4) A complex array of vertical and horizontal soil springs surrounding the mat foundation and concrete grade beams; 5) Separate soil springs for caissons penetrating layers of disturbed soil and embedded in fractured shale; 6) Latest code requirements for analysis of accidental torsion, amplified torsional effects, and orthogonal earthquake load combinations for rigid diaphragms; 7) Substantial concern for accurate determination of seismic effects at steel beam to masonry wall connections that have limited ductility, under a multitude of load combinations.

Figure 1: Structural rendering of generator building with roof deck removed.

Instead, a concrete slab was assumed with material characteristics that allowed the model to replicate the stiffness and strength of the actual concrete-topped steel deck as specified on the design drawings. Three trials led to the selection of density, elastic modulus, shear modulus, and Poisson’s ratio for the concrete deck to replicate the diaphragm stiffness that was previously calculated using the flexibility factors documented in the International Code Council Evaluation Report for the deck.

Design codes specify that “cracked” masonry and concrete should be assumed in the seismic design. Based on ACI 318 Sect. 8.7 and ACI 530 Sect. 1.9 commentary, this requirement for reduced stiffness was achieved by reducing the moduli of elasticity and shear, and using the corresponding Poisson’s ratio. Masonry design codes report a broad range of values for these moduli, and mid-range values were selected for a fully grouted and reinforced wall with pilasters.

Geotechnical Requirements and Software Issues The geotechnical consultant provided vertical capacities for the 30-inch-diameter caissons and indicated that the shafts would need to extend 8 feet to bedrock, and 5 to 10 feet into the fractured shale.

Model Setup and Material Selection The model setup was primarily accomplished using the software’s graphical user interface, occasionally in combination with the text editor. Roof deck, masonry walls and concrete mat were modeled as plates two feet square.

Structural steel roof purlins and girders were assumed initially, and the program selected them during the final analysis based on AISC design parameters. Dimensions for masonry wall pilasters, concrete grade beams, and caissons were initially assumed as well. Concrete portal frames were placed around the large louvered openings in the east and west bearing walls. Building dimensions were frequently revised during the early design stages by other engineering disciplines. It was relatively easy to keep pace with these model changes by selecting the entire geometry for the affected portion of the structure and then moving it.

The author selected 1½-inch deep steel roof deck with 5¼-inch reinforced concrete topping and, based on experience, decided that the beam sizes would be relatively light and not of the magnitude that would economically justify activating the available beam/deck composite design tools.

STRUCTURE magazine

Figure 2: Maximum roof diaphragm shear in north-south direction.

42

March 2013

Figure 3: West wall maximum north-south seismic shear.

Soil improvement was not feasible due to the multitude of existing buried utilities. The consultant provided stiffness values for horizontal and vertical “soil springs” for the mat, caissons, and grade beams, which were modeled initially as “compression only” springs.

During insertion of the horizontal springs at grade beams, it became apparent that these springs would override the vertical springs that had been previously assigned to the same nodes for the slab. With the assistance of Bentley Technical Support, the author determined that the springs could be reinstated by inserting the spring values in the text editor instead of the graphical interface. Bentley indicated that this anomaly would be resolved in the next release of the software.

The soil springs also resulted in a few “instability warnings” during initial analyses. Again with assistance from Bentley Technical Support, the author determined that these “warnings” could be eliminated if the “compression only” assignments were removed from support specifications prior to the primary load case listing, and re-inserted as “changed supports” in the text editor immediately prior to the list of load combinations.

Benefits of the Model The structural model facilitated many aspects of the design process, including: A. Heavy equipment is suspended from the roof beams, and seismic effects on the diaphragm could be accurately assessed (Figure 2).

B. The code required measurement of drift in multiple locations. Model analysis made it possible to quantify values at any location under all load cases.

C. It was not difficult to measure stresses around large openings in shear walls (Figure 3) D. Precise stress patterns in the software’s post-processor enhanced economical placement of reinforcing (Figure 4 ).

E. It was possible to evaluate reactions for caissons under any load combination, and confirm adequate resistance to lateral loads and uplift.

F. Post-processing confirmed that masonry “breakout” stresses at steel beam and strut connections were within allowable values. Slip connections were provided where wall restraint would otherwise be inadequate.

Figure 4: Maximum shear stress in ground floor slab.

non-symmetrically placed. Also, reliable assessment of potential uplift and horizontal soil support was mandatory. To address this challenge, the author used the system of “Seismic Permutations” documented in the STAADPro technical reference documents.

More than 40 load cases were employed to assess torsional and extreme torsional irregularity; implement code requirements for redundancy, accidental eccentricities, and amplified torsional effects; and combine effects orthogonally. For the Generator Building, the task became easier when permutations were copied from a template that had been developed, improved, and updated iteratively during prior projects; pasted in the new project’s text editor; and re-factored for the requirements of the new structure. For example, model analyses concluded that torsional irregularity did not exist in the X-direction, but did exist in the Z-direction, and accidental loading in that direction also had to be amplified. Extreme torsional irregularity was shown to be non- existent in either direction. Code requirements also dictated that a redundancy factor of 1.3 had to be applied for load combinations in the Z-direction.

Conclusion Understandably, some structural engineers could argue that the time spent in setting up a computer model is not always justified, nor is precise analysis always required. However, on many projects, time spent on this task – especially after reusable templates have been developed on prior projects – could amount to less time than would be spent using conventional spreadsheets, and final results could provide the project owner with greater value. Nevertheless, many initial templates can be like “black boxes” and checking with conventional spreadsheets (as done on this project) is essential.

The population in the South San Francisco area will rely on the Generator Building and its equipment to provide power and water during earthquakes that are not uncommon to the region. Modeling and analysis provided assurance that the source of this service will be sustained, even in the event of an extreme emergency.

Comparable modeling efforts may be indispensable as seismic requirements and design codes continue to grow in magnitude and complexity.▪

Seismic Permutations Model analysis enabled the project design to meet the relatively complex seismic requirements of ASCE 7-05 and the California Building Code. Accurate analysis of the caissons between existing utilities presented a unique challenge because the caissons were shallow and STRUCTURE magazine

43

Louis Scatena, P.E. (LScatena@carollo.com), is a senior structural engineer with Carollo Engineers, Inc. He has 25 years of experience in the design of public buildings and water treatment facilities in the United States.

March 2013

Structural DeSign design issues for structural engineers

I

t’s amazing that something as simple and as common as wood-framed stair stringers do not yet have specific prescriptive code construction provisions. Despite the commonality of wood-framed stair stringers, they still suffer from structural performance issues which result in scenarios that range from cracked drywall to severe injuries. While the International Code Council (ICC) recently moved to address lateral residential deck failures by bolstering the prescriptive requirements of Section R502.2.2 in the 2009 International Residential Code (IRC), there still remains a void in an area where a few simple changes could make a dramatic difference.

According to the U.S. Consumer Product Safety Commission (CPSC) National Electronic Injury Surveillance System (NEISS), during 2008 through 2011, there were an estimated 10,000 instances nationally where an individual visited an emergency room with injuries related directly to a structural failure of wooden stairs. A cursory review of these instances reveals that the majority of those are related to wood tread failure and the minority related to wood-framed stringer failure. This article focuses on the design and construction of wood-framed stair stringers, through a review of current code requirements and rules-of-thumb; common structural performance issues; structural analysis considerations and examples; and, recommendations for mitigating this common construction deficiency.

Wood-framed Stair Stringer Design and Construction

By Christopher R. Fournier, P.E.

Code Requirements Christopher R. Fournier, P.E. is a Senior Structural Engineer at H.E. Bergeron Engineers, Inc. in North Conway, NH. He can be reached at cfournier@hebengineers.com.

The ICC family of codes, the IRC and International Building Code (IBC), contain very few provisions regarding wood-framed stair stringer design and construction. Live loading is specified as 40 pounds per square foot for residential applications and 100 pounds per square foot for other applications (IBC Table 1607.1). The majority of the

code provisions address dimensional restraints, such as width, rise/run, and vertical clearance.

Table 1 provides a summary of code requirements as well as some carpentry and building construction handbook recommendations for the dimensional restraints of stair rise and run.

Essentially that’s it. The codes provide tables for prescriptively selecting the sufficient span of joists, rafters, girders, and headers for simple structural loading, but only provides limited dimensional restraints for stair construction. The only guidance provided to a builder for the structural capability (minimum throat depth) of woodframed stair stringers comes from a carpentry handbook. Otherwise, it is left to the builder’s common sense, experience, and available rulesof-thumb to prevent the stringers for a 10-foot flight of stairs to be constructed from two 2x8s.

Common Structural Performance Issues Connections Perhaps the most critical structural issue of woodframed stair construction is the connection of the stair stringer to the supporting structure. More often than not, the lower end of a set of stringers is in direct bearing contact with its supporting structure and issues tend not to arise. Typical construction employs the use of a thrust/kicker block to prevent axial movement. More often, the most important connection is at the upper end of the stairs where the stringers are typically flush-framed to a header. Failure of this connection is often sudden and catastrophic, resulting in severe injuries. One recently documented instance resulted in serious injuries to several firefighters who were carrying an injured resident out of the home (Hench D., 2010).

Prescriptive fastening schedules in the IRC and IBC offer connection specifications for similar situations, such as a joist flush-framed to a header or girder (IRC Table R602.3(1) and IBC Table 2304.9.1). These connections entail

Table 1: Dimensional rise and run requirements/recommendations from various sources.

Riser

Flight Rise

Max. (inches)

Min. (inches)

Max. (inches)

Min. (inches)

Max. (feet)

-

7.75

10

-

-

12

4

7

11

-

-

12

Handbooks

6

8

9

12

3.5

12

Architectural Graphics Standard (1988)

5

9

8

16

-

12

IBC 2009 1

1

Throat Depth

Min. (inches) IRC 2009

The website version of this article contains detailed references. Please visit www.STRUCTUREmag.org.

Tread

Dietz (1954); Feirer and Hutchins (1976).

44 March 2013

Notching

Figure 1: Effect of overcutting notches on effective throat depth.

face-nailing or toe-nailing; however, these connections cannot be directly applied to the upper connection of stair stringers because of their sloped grain condition. Another method of construction employs the use of a ledger to provide direct bearing for the stringers. This method can be suitable, but prescriptive provisions do not exist and need to be provided. With the widespread use of mechanical connectors in other aspects of modern wood-framed construction, it makes good sense that these could be used for this situation. Sloped sawn lumber face-mount hangers are common, simple to install, field adjustable, and capable of safely handling the connection forces from most wood-framed stringer applications.

The overcutting of notches at the tread/riser intersection during the construction of stair stringers is a common problem with unskilled or careless carpenters, as shown in Figure 1. In this instance the notches are overcut by threequarters of an inch and unnecessarily reduce overall stringer strength. A less common, but largely more effective approach is to drill a one-quarter inch hole at the notch corner and cut to the hole with a handsaw or skillsaw.

In both instances, the effective throat of the stringer is less than the theoretical throat.

However, the drilled hole and careful cutting minimize the strength reduction and provides relief for the stress concentration created as a result of notching.

Deflection Deflection of stair stringers is largely ignored in typical construction, but code required limits should be applied. While prescriptive provisions of the IRC provide no explicit restrictions on deflection, the IBC provides deflection limits (Table 1604.3) for various situations. From this table, the most applicable limits for stair stringers are L/360 for live loads and L/240 for total load. Total load can be used as the live load plus half of the dead load for wood with moisture ADVERTISEMENT - For Advertiser Information, visit www.STRUCTUREmag.org

STRUCTURE magazine

45

March 2013

Figure 2: Cracked drywall caused by excessive deflection.

content below 16% at the time of installation (IBC Table 1604.3 note d). These limits are intended to reduce serviceability issues due to cracking of finishes and improve perception of structural performance among other things. As an example, Figure 2 shows cracking of a taped drywall joint beneath a set of underperforming stair stringers. Drywall directly applied to the bottom of the stringers has moved excessively, causing a failure of the joint and an unsightly crack. Figure 3 (page 46) shows recent failure of a caulked joint between a tread and drywall of the same set of stairs. This finishing detail is common

in lower-end construction. However, excessive deflection is less noticeable in typical higher-end construction where molding is attached to treads and specifically not attached to walls. Damage to finishes can be temporarily fixed, but will reappear without addressing the root of the problem, which is insufficient stringer stiffness.

may bear an equal share. By isolating the riser as shown in Figure 4, analysis demonstrates this equal share in a common situation. In theory this equal distribution does not occur, but with a sufficiently stiff riser the distribution can be assumed uniform and therefore more conducive to prescriptive provisions.

Inclined Beam Design

Structural Analysis

Because stair stringers are typically axially restrained at each end, it is prudent to review the comparison of the sloping beam method and the horizontal plane method. With the sloping beam method, the uniform load is resolved into components of load perpendicular to the longitudinal axis of the beam (bending) and parallel to the longitudinal axis of the beam (compression), and the span length is to be considered the inclined span.

Load distribution Figure 3: Cracked caulk caused by excessive deflection. With the horizontal plane method, uniform load is applied directly to the horizontal span In a theoretical three stringer configuration, of the inclined beam. It has been shown that one may be tempted to apply twice the tributhe two methods result in very similar bendtary load to the center stringer as to the exterior ing moment and shear values (Breyer et. al., stringers. Doing so would result in an unrea2003), but also that the axial compression sonably stout center stringer and does not lend portion of the sloping beam method is insigitself easily to prescriptive provisions. However, nificant when considering the interaction of when considering the contribution of the riser Figure 4: Stringer load distribution with a compression and bending. For the purposes of and in a lesser part the tread to load distribu- sufficiently stiff riser. this article, the horizontal plane method will tion, it is feasible to assume that the stringers be used due to its simplicity, popularity, and relative accuracy.

PAUL G. ALLEN CENTER FOR GLOBAL ANIMAL HEALTH AT WSU / PHOTO: BENJAMIN BENSCHNEIDER The following analysis demonstrates results of a typical wood-framed stair stringer configuration as well as several similar configurations. Consider 15 risers at 7¼-inch tall with 10½-inch wide treads and stringers cut from SPF No. 1/No. 2 2x12s. This configuration results in an effective throat depth of approximately 5 inches for a horizontal span of 12 feet and 3 inches. For a residential loading of 10 pounds per square foot dead and 40 pounds per square foot live and a one-foot tributary width (3-foot width with 3 stringers), the allowable bending strength ratio is 145% and the shear strength ratio is 50%. Live load deflections and total load deflections are 0.93 inches and 1.05 inches respectively, which are 127% and 72% more than the allowable limits of 0.41 inches and 0.61 inches. As discussed previously, SEATTLE DAILY JOURNAL OF COMMERCE excessive deflections are demonstrated and BUILDING OF THE YEAR AWARD can be exacerbated by being exposed to the elements and experiencing a moisture content above 16% during construction. In which case, the total load deflection would increase to 1.16 inches which is 90% above Seattle Portland San Francisco San Diego St. Louis Long Beach the allowable limits.

Tacoma Eugene Pasadena Boise Chicago Walnut Creek For comparison, Table 2 summarizes Lacey Sacramento Irvine Phoenix New York Los Angeles results from several additional analyses: stringers cut from 2x10s; 2x12 stringers

ADVERTISEMENT - For Advertiser Information, visit www.STRUCTUREmag.org

Without a published or publically accepted method for analysis of wood-framed stair stringers, the method of analysis used for the purposes of this article will be to ignore any contribution of stringer material outside the effective depth. Without performing an extensive finite-element analysis of the notched profile, it is believed that very little integrity is added from the notched material.

STRUCTURE magazine

46

March 2013

with 2x6s sistered to the effective depth region; 2x12 stringers with a 2x4 strongback on the bottom; and stringers cut from a 1½-inch by 117/8-inch engineered wood product (EWP).

The only configurations from this typical example that fully comply with the code requirements using this method of analysis are the 2x12 stringers with 2x6 sistering or with a 2x4 strongback.

Table 2: Analysis results for multiple configurations of the example problem.

Recommendations In an effort to mitigate one of the remaining all-too-common life safety issues in woodframed construction, a concerted effort should be put forth to provide additional prescriptive provisions. The following action items are recommended: 1) Require that mechanical connectors be used for the upper end stringer connections, in a similar fashion that mechanical connectors have been implemented with deck lateral load connections. Both situations have a history of sudden and catastrophic failures which can be mitigated by the requirement of a well-controlled consistent connection method.

2) Supply prescriptive span tables “stair stringer spans for common

1 2

Bending Strength Ratio

Shear Strength Ratio

Live Load Deflection (inches)

Total Load Deflection (inches)

Code Limits

100%

100%

0.41

0.61

2x12

145%

50%

0.93 (227%)

1.05 (172%)

2x10

602%

82%

4.29 (1046%)

4.83 (792%)

2x12 with sister

71%

50% 2

0.40 (98%)

0.45 (74%)

2x12 with strongback

70%

50% 2

0.29 (71%)

0.33 (54%)

Engineered wood product 1

40%

15%

0.54 (132%)

0.61 (100%)

EWP: Fb=2650psi, Fv=400psi, E=1,700,000psi Shear strength is not increased for reinforced stringer as the reinforcement does not need to extend full length, where maximum shear stresses occur.

lumber species” in the IRC and IBC based on effective throat depth.

Separate tables for unreinforced, and reinforced spans should be provided. Nailing patterns for reinforced conditions should also be provided, appropriately in a fastening schedule.

3) Provide minimum riser and tread material and section limits to ensure that uniform load distribution occurs between stringers in a flight

of stairs. Whether it is provided by conventional oak riser and treads, sheathing, or dimensional lumber, guidance should be provided.

4) Strongly recommend a ¼-inch drilled hole at the notch corner during construction of wood-framed stringers. Consequently, implement a code-required one-quarter inch reduction from the theoretical throat depth to the effective throat depth during the design process.▪

ADVERTISEMENT - For Advertiser Information, visit www.STRUCTUREmag.org

HIGH-STRENGTH CONNECTORS Meets all F d OCB B SC F an ts of en m require 341 C IS A

BETTER . SIMPLER . LOWER COST ▪ Pre-designed and detailed connections dramatically reduce engineering time and effort ▪ Modular design minimizes detailing and accelerates fabrication ▪ Elimination of field welding reduces the cost of erection and special inspection ▪ Rest assuring using standardized, laboratoryproven connections

STRUCTURE magazine

47

March 2013

Just the FAQs questions we made up about ... STEEL

S

teel deck is often installed using arc spot welds, either with or without weld washers. Arc spot welds, often referred to as “puddle welds”, are similar to plug welds except that the thin top sheet does not require a hole to be pre-punched prior to welding. This article will focus on what an arc spot weld is, how the weld is made, and how to ensure quality welds are produced.

How Are Arc Spot Welds Made?

The arc spot or “puddle” weld is started by striking an arc on the deck surface, causing a hole to form in the deck. The weld operation then continues by depositing electrode material on the beam or joist and allowing the molten “puddle” to engage the penetrated deck. It is essential that the finished weld penetrate into the supporting beam or joist and that the puddle engage the deck on the weld perimeter. The complete welding process usually requires 3 to 6 seconds, or perhaps more on multiple deck thicknesses or thicker deck.

Research has shown that arc spot weld times and weld quality can vary substantially depending on the welding equipment and technique used to produce the welds. This process requires a welder who is qualified to make these specific welds. Arc spot welds can be made through multiple thicknesses of steel deck, as long as the total base metal (bare steel) thickness of the deck does not exceed 0.15 inches.

Arc-puddle welding methods and operator qualifications are described in the American Welding Society Structural Welding Code Sheet Steel, AWS D1.3. The essential issue in forming a good weld rests in bringing the deck and the supporting beam or joist to fusion temperature at the same time, avoiding “burn-out” in the sheet, with adequate penetration into the beam or joist, and with proper puddle engagement on the weld perimeter.

Quality welded connections require that the elements to be joined be in intimate contact for proper heat transfer; seldom can a gap between the deck and the beam or joist be bridged with electrode material. The operator must select weld machine power settings sufficient to provide energy levels to raise the deck and beam or joist to fusion temperature while preserving the integrity of the hole formed in the steel deck.

Arc Spot Welding Steel Deck – A Primer

By Thomas Sputo, Ph.D., P.E., S.E., SECB

Thomas Sputo, Ph.D., P.E., S.E., SECB is the Technical Director of the Steel Deck Institute, a trade organization of steel deck manufacturers. Additionally, he is a consulting structural engineer with the Gainesville, FL firm of Sputo and Lammert Engineering, LLC, and a Senior Lecturer in the Department of Civil and Coastal Engineering at the University of Florida.

What are Weld Washers?

Weld washers are small elements of sheet steel with a punched hole at their center and may be curved to fit into the valleys of deck panels.

48 March 2013

Arc spot weld with weld washer.

Arc spot weld.

Washers may be of differing thickness and have different hole diameters or hole shapes. The most common type is approximately 0.06 inches thick with holes of 3/8-inch in diameter and a minimum ultimate strength of 45 ksi, and may be designated as 3/8-inch x 16 gage washers. Weld washers are laid in position on the deck units, an arc is struck on the sheet inside the hole, and the operation continues usually until the hole is filled. The weld washer acts as a heat sink and retards burn-away of the sheet. The washer permits welds in thin deck that might otherwise burn away from the welding operation faster than weld material can be deposited.

Should Weld Washers Be Used for All Deck Welding?

Not necessarily.

It is essential to understand the heat issue in welding. The weld washer acts as a heat sink, drawing some of the heat and therefore reducing the energy delivered to the substrate, compared to that delivered in arc-spot welding without washers. For a particular application, a five second welding time may be adequate to form a high quality weld through a weld washer into steel deck thicknesses between 0.015 and 0.028 inches.

However, using the same washer type and the same welding rates with a thicker steel deck panel may severely limit heat available for penetration into the substrate. Without sufficient heat, a weld washer used with thicker deck can actually prevent adequate heating, with resulting poor weld penetration and poor weld quality.

Each deck installation contractor must be responsible for inspection and testing of WPS qualification tests and welder performance testing as described in AWS D1.3. Arc spot weld WPS are not described in Clause 3 of AWS D1.3 and, therefore, must be qualified by testing and recorded on a Procedure Qualification Record (PQR.)

Typical weld washer.

It is not uncommon for the washer to reduce or virtually eliminate fusion to the substrate when welds are made through sheets of 22 gage (0.0295 inches) or thicker deck.

Typical 3/8-inch x 16 gage (0.060 inches) washers are not recommended with deck design thicknesses equal to or greater than 0.028 inches because their use may actually reduce the weld penetration. Weld washers are recommended for welding in deck panels thinner than 0.028 inches.

An excellent reference for additional information is the SDI White Paper, Arc-Puddle Welds and Weld Washers for Attachments in Steel Deck, available for free download from the SDI website (www.sdi.org).

What is the Most Common Filler Metal?

The most common filler metal used for welding steel deck is an E6022 electrode, due to the ability of that electrode to produce welds with good penetration and wetting of the weld puddle perimeter. Additionally, load tables for most roof deck and some non-composite (form) deck are based on a specified minimum yield strength of 33 ksi. Accordingly, an E6022 electrode is the “matching” electrode for composite deck, roof deck, and non-composite floor deck with thicknesses of 22 gage or greater.

Deck thinner than 22 gage is usually manufactured from steel with higher yield strength, therefore E7014 electrodes are recommended with weld washers. Electrodes with strengths greater than 70 ksi are not necessary because the heat produced by the welding will anneal the deck in the vicinity of the weld, locally reducing its ultimate strength.

Additionally, the use of low-hydrogen electrodes is seldom necessary, and may actually reduce the weld quality due to the higher amperages usually required for these electrodes.

What Welding Parameters Should be Used?

Required welding machine power settings usually are well below those needed for welding in hot-rolled steels. The settings should be such that electrode burn-off rates are between 0.15 inches and 0.25 inches of rod per second in typical

What Inspection is Required for Deck Welding?

Field quality check procedure.

E6022 or E7014, 5/32-inch diameter rods. The time required per weld may vary between 3 to 6 seconds or more, depending on the properties of parts being connected. Heavier support steel requires more welding time, but increased power settings may burn out the deck faster than electrode material can be deposited.

A preliminary field quality check can be made by placing a pair of welds in adjacent valleys at one end of a panel. An inspection should show the weld material in fused contact over most of the weld perimeter. Spotty contact may indicate power settings that are excessive. The opposite end of the panel can be rotated, within the panel plane, placing the welds in shear, and continued rotation can lead to separation. Separation, leaving no apparent external perimeter distress but occurring at the sheet-to structure plane, may indicate insufficient welding time and poor fusion with the support steel. Failure around the external weld perimeter, showing bearing deformations within the panel, but the weld still attached to the support steel, indicates a higher quality weld. The ending of the welding operation may not permit complete fusion on the whole perimeter. Good fusion should be visible over no less than 90 percent of the weld perimeter (Clause 6.1.1.4 of AWS D1.3 permits undercut on 12% of the weld perimeter).

Are Welding Procedure Specification (WPS) Documents Required?

Yes. The deck installation contractor is responsible for following AWS D1.3 and Welding Procedure Specification (WPS) documents. A WPS is a detailed document providing required variables for a specific welding application to assure repeatability by properly trained welders and welding operators. WPS documents must be written for all welds permitted as prequalified and all welds qualified in conformance with Clause 4 of AWS D1.3.

STRUCTURE magazine

49

March 2013

Visual inspection is required to determine if a weld meets the acceptance criteria of AWS D1.3. It is the deck installation contractor’s responsibility to ensure that all WPSs and welders are qualified. The EOR may accept previously qualified or prequalified WPS. However, if the EOR does not accept such evidence, the deck installation contractor must successfully complete the required tests prior to welding.

The SDI has developed the ANSI/SDI QA/ QC-2011 Standard for Quality Control and Quality Assurance for Installation of Steel Deck, which provides requirements for steel deck installation quality in a mandatory format that can be used for inspection purposes.

This Standard is available for free download from the SDI website (www.sdi.org) and it is highly recommended that designers require compliance with the quality procedures in the standard through incorporation of the standard in project specifications.

What are the Key Take-Away Points?

1) Arc spot welding is a viable method of deck attachment, however weld quality must be monitored.

A proper arc spot weld requires between 3 to 6 seconds, or perhaps longer, depending on the total deck thickness, welding equipment and settings, and environmental factors. It is impossible to make a proper weld with proper fusion in less time. Arc times should be monitored as one aspect of project quality control.

2) Weld washers, due to their heat-sink effect, may actually create welds of lower quality and strength when used with 22 gage or thicker deck. Do not specify weld washers with 22 gage deck.

3) Contractually require the use of the ANSI/SDI QA/QC-2011 Standard for Quality Control and Quality Assurance for Installation of Steel Deck to promote quality in deck installation.▪

HIT-HY 200 Adhesive Anchoring System

One giant leap.

Introducing the world’s first non-cleaning adhesive anchoring system.

Once in a blue moon something comes along with the power to change the way we work. The HIT-HY 200 Adhesive Anchoring System featuring Safe Set™ Technology does just that. This innovative, new system eliminates an important and load-critical step of the installation process: manually cleaning the hole before injection of the adhesive. It's one small step in the construction process and a giant leap forward in reliability.

For HIT-HY 200 technical data and more information about Safe Set™ Technology and how it works, visit www.us.hilti.com/HY200.

Hilti. Outperform. Outlast.

Hilti, Inc. (U.S.) 1-800-879-8000 www.us.hilti.com/HY200 • Hilti (Canada) Corp. 1-800-363-4458 www.hilti.ca/HY200

Historical use of PowerActuated Fasteners (PAFs) Power-actuated fasteners, also called power-driven fasteners, DX/GX fastening systems or shot pins, have been used for decades and are routinely used on today’s construction projects in a wide variety of applications.

These types of fasteners are typically proprietary systems manufactured from hardened, ductile steel wire with small, but very significant features including full-tip knurling, Figure 1: Powder-Actuated Fasteners (PAFs) – an efficient, reliable special fastener point geometry and and safe fastening method. pre-mounted washers. Driven by powder cartridges, compressed gas or air, power-actuated fasteners offer an efficient, Power – Driven into Concrete Steel and Masonry reliable and safe method for attaching many Elements. A key part of this update includes prodbuilding materials to steel, concrete or masonry. uct evaluations to International Building Code Power-actuated tools are available as single shot, (IBC) 2012 including the ASCE 7-10 Minimum semi-automatic and automatic magazine tools, Design Loads for Buildings which can increase productivity. and Other Structures referPower-actuated fasteners are used in lateral force ence standard. ASCE 7-10 resisting structural systems such as untopped Section 13.4.5 includes some and concrete filled steel deck, and wood struc- new exception language tural panel diaphragms and shear walls. In these pertaining to nonstructural applications, multiple power-actuated fasten- component attachments in higher Seismic Design ers installed at specified patterns and spacings Categories D, E and F. This clarification helps provide the strength and stiffness to the given establish certain nonstructural component fastenstructural system. Structural behavior and per- ing applications where power-actuated fasteners formance with power-actuated fasteners is well are deemed acceptable. Over the years, some known and established based on small scale and confusion seemed to develop relative to powerlarge scale assembly tests. actuated fasteners versus new concrete anchorage Nonstructural systems are separate from struc- design requirements, but the ASCE 7 clarifying tural systems, and a clear distinction is made in language now serves as a placeholder until more the building codes and standards. Nonstructural comprehensive seismic qualification test proceapplications may involve suspended ceilings, dures for power-actuated fasteners are developed conduit attachments, mechanical, plumbing, and implemented. electrical and communications equipment, coldThe ASCE 7-10 Section 13.4.5 exception formed steel track attachments and architectural addresses the use of power-actuated fasteners in components, and other applications that are not applications that do not involve sustained tension part of the structural systems. Nonstructural dis- loading or bracing. For Seismic Design Categories tributed systems are also frequently attached with D, E and F, the default allowable load limits are power-actuated fasteners in redundant grid like set at 90 pounds in concrete and 250 pounds in arrangements or linear patterns. These applica- steel per individual fastener. Manufacturer pubtions are also important to performance of the lished data or ICC-ES AC70 Evaluation Service overall structure; however, they generally don’t get Reports (ESRs) provide the recommended allowas much attention or focus by the design team. able loads for fastening applications. ICC-ES Recent updates to building code provisions and AC70 ESRs have been issued under the IBC ongoing university research are helping the indus- 2012 and incorporate the ASCE 7 reference try and structural engineers understand more standard exception language. These reports are about power-actuated fasteners in nonstructural available at www.icc-es.org or on the manufacapplications going forward. turer’s websites.

As part of the AC70 update, ICC-ES also clarified the use of power-actuated fasteners Clarifying the Seismic Grey Zone for attachment of cold-formed steel tracks in At the request of practicing structural engineers partition walls. For interior, nonstructural walls and Hilti, Inc., International Code Council that are not subject to sustained tension loads Evaluation Services (ICC-ES) recently updated and are not a bracing application, power-driven their Acceptance Criteria (AC) 70 for Fasteners fasteners may be used to attach steel track to

InSIghtS new trends, new techniques and current industry issues

Power Forward

STRUCTURE magazine

51

Driving Power-Actuated Fastener (PAF) Code Provisions

By William Gould, P.E. and Drew Liechti, P.E.

William Gould, P.E. is a Director of Codes and Approvals at Hilti. He may be reached at william.gould@hilti.com.

Drew Liechti, P.E. is a Manager for Technical Services at Hilti. He may be reached at drew.liechti@hilti.com.

Hilti Power-Driven Fasteners

concrete or steel in all Seismic Design Categories. In Seismic Design Categories D, E, and F, the allowable shear load due to transverse pressure shall be no more than 90 pounds when attaching to concrete; or 250 pounds when attaching to steel. Coupled with published spacing installation guidelines, this new language should help structural engineers with future designs of these common wall systems in higher seismic areas.

Next Steps for PowerActuated Fastener Evaluations

3,000 psi Lightweight Concrete

min. 3-1/4" 3"

1-1/8" Min. Edge Distance

4-1/2" min.

4-1/2" min.

7-1/4" min.

Direction of tension load on fastener

Figure 3: Power-actuated fasteners in concrete over metal deck.

:

Structural project manager Structural eit

JQ is a multi-office firm providing structural engineering, civil engineering, land surveying, and facility assessments throughout Texas and the southern United States. Our San Antonio office is currently seeking applicants with the following qualifications:

•

Direction of shear load on fastener

Form Deck Lower Flute Location Upper Flute Location

In conjunction with the update of AC70 to the IBC 2012, Hilti, Inc. also proposed a new seismic qualification procedure for poweractuated fasteners in steel base materials in 2011. This procedure assesses the residual static load performance of power-actuated fasteners after simulated seismic loads are applied to the test fasteners using a step-wise pulsating tension load or alternating shear load modeled after concrete anchor seismic tests. Initial research into the feasibility of this evaluation approach is favorable and confirms minimal to no reductions from published static allowable loads in steel. This is due to the very reliable anchorage mechanisms that are developed when power-actuated fasteners are installed in steel, including friction welding, keying and brazing effects. Preliminary test results also confirm what has been historically approved for steel diaphragms and shear walls subjected to seismic forces.

•

12"

Structural Project Manager: 5 years or more experience as a Structural Project Manager post licensure Structural EIT: 3 to 4 years of design experience preferred

For details of duties and responsibilities, please visit our website at www.jqeng.com.

Candidates fulfilling the above requirements should send their resume to sanantonioinfo@jqsatx.com

ICC-ES is currently reviewing the seismic test proposal, and the general timeline involves discussion in public hearings with implementation as soon as 2013. Future seismic qualification procedures for nonstructural system applications in concrete base materials will be the next step on the journey towards more complete seismic qualification of power-actuated fasteners.

Diving Deeper with University Research

Seismic research involving the use of power-actuated fasteners as part of structural and nonstructural systems continues and is helping to strengthen performance expectations.

In 2012, the Building Nonstructural Component and System (BNCS) seismic research project sponsored by the National Science Foundation (NSF) and Network for Earthquake Engineering Simulation (NEES) at the University of California San Diego involved the use of power-actuated fasteners for nonstructural systems including suspended ceilings, cold-formed steel interior partition walls, exterior balloon framing walls and electrical conduit attachments. The initial results are promising and should provide additional confirmation that power-actuated fasteners are reliable seismic attachment methods for certain applications. (http://bncs.ucsd.edu/index.html).

Seismic research involving suspended ceilings and partition walls with power-actuated fasteners is ongoing in 2013 as part of the NEES Nonstructural System Grand Challenge research project at the University of Nevada–Reno (http://nees-nonstructural.org/).

Additionally, another critical seismic research project involving powder-actuated fasteners is ongoing at Virginia Tech, investigating the effect of power-actuated fasteners on protected zones of steel moment frames (www.eatherton.cee.vt.edu). Hilti, Inc. is also conducting parallel research to extend power-actuated fastening technology and applications as part of diaphragms, shear walls and nonstructural component fastenings. All of this research is aimed at developing more efficient and predictable connection methods for structural engineering applications in the future.▪

austin | dallas | fort worth | san antonio www.jqeng.com

STRUCTURE magazine

Figure 2: Robust anchorage – poweractuated fastener in steel.

52

March 2013

Code Updates

code developments and announcements

AISI 202-11

Code of Standard Practice for Structural Cold-Formed Steel Framing

By Jeffrey M. Klaiman, P.E.

C

old-formed steel (CFS) framing is a bit of a unique product among the many other systems that comprise the structural elements of a building. It can be an industry standard shape, or one of a variety of proprietary products that are available. It can be designed and specified by the structural engineer of record, or it could be delegated to a specialty engineer specific for the CFS system or CFS component assembly. It can be a standalone system in a structure, or it can be part of a much bigger system, such as the overall lateral stability system. All of these variances, and many others, can make it hard for all the parties involved in the design and construction of a project to understand their individual responsibilities with regard to its use.

In the early twenty-first century, the American Iron and Steel Institute (AISI) set out to help clarify CFS framing responsibilities by developing its own Code of Standard Practice for Cold-Formed Steel Structural Framing (COSP).

The first edition of the document was published in 2005, closely followed-up with an updated edition in 2006. In 2011, the most current edition was published. It’s official ANSI designation is AISI 202-11.

What it Does The purpose of the COSP is very simple – to help answer the age-old question, “Who is responsible for what?” It defines and sets forth accepted norms of good practice for design, fabrication and installation of cold-formed steel structural framing. It is not intended to conflict with or supersede any legal building regulations or contractual relationship, but serves to supplement and amplify such laws and is intended to be used unless there are differing instructions in the contract documents. This voluntary document is intended to be used by owner’s representatives, design professionals, contractors, construction managers, suppliers, manufacturers, installers and others on individual projects that utilize cold-formed steel structural framing.

How it Was Developed The AISI began development of the COSP in 2002 in a newly formed subcommittee under the auspices of its Committee on Framing Standards. A wide variety of

interests participated in the development of this document to ensure that all parties in a construction project were represented and fairly dealt with. Represented were architects, engineers, material manufacturers, material suppliers, component manufacturers, installers/erectors and many associated organizations, including the Natioinal Council of Structural Engineers Associations (NCSEA), Steel Stud Manufacturers Association (SSMA), Steel Framing Industry Association (SFIA) and Structural Building Components Association (SBCA).

The AISI COSP was modeled after other already available and well-regarded similar documents, most notably those published by the American Institute of Steel Construction (AISC) and Steel Joist Institute (SJI). In addition, other documents were reviewed, including several published by the Council of American Structural Engineers (CASE). The CASE documents that were directly related were the National Practice Guidelines for Specialty Structural Engineers, National Practice Guidelines for the Structural Engineer of Record and A Guideline Addressing Coordination and Completeness of Structural Construction Documents.

The first two editions of the COSP were developed under a consensus system, but the 2011 edition has taken this to a new level of distinction by being approved by ANSI as an American National Standard. While it is not a mandatory document per any national building code, it can be invoked by any party involved in a project. The provisions specific to component truss assemblies have been extracted from the COSP and appended to the AISI Truss Standard (AISI S214), which is a mandatory document referenced by the national building codes.

Finally, each edition of the COSP has been reviewed and endorsed by a growing group of associated organizations, including the Association of the Wall and Ceiling Industry (AWCI), ColdFormed Steel Engineers Institute (CFSEI), Steel Stud Manufacturers Association (SSMA), Steel Framing Industry Association (SFIA), Structural Building Components Association (SBCA) and Steel Framing Alliance (SFA).

There is too much information in the document to be discussed in one article. As this magazine is a publication for engineers, this article will focus on several representative items discussed in the COSP for engineers that may be involved in a project with CFS framing.

STRUCTURE magazine

54

March 2013

Key Responsibilities of the Building Designer The responsibility for design of cold-formed steel framing may be assigned by performance specification in the contract documents to a number of parties, but the overall project responsibility remains with the design professional of record.

The contract documents are assumed to be correct and constructable and the CFS specialty designers/engineers (if applicable), component manufacturers (if applicable) and installer are only responsible to design and furnish materials in accordance with these documents. Above all, the indicated use of cold-formed steel framing must be reasonable. The Building Designer may not be providing the complete design of the cold-formed steel framing, but they must take care to show a concept that can be designed and is within the ability for the CFS framing to adequately be used. Otherwise, once the specialty engineer starts their design, RFIs and change orders will start piling up.

The contract documents must include all the information required by the CFS specialty engineer to do their work, including all required design criteria. If the project includes cold-formed steel shear walls or braced walls, the contract drawings must provide the relevant design information required for the CFS specialty engineer to design these items, such as locations, lengths and loads to be expected at each location. If the project includes the layout and design of trusses that will be delegated to a specialty truss designer/engineer, the contract documents must provide the following information: conceptual orientation and location of trusses and girders, bearing locations, truss design loads and/or criteria as well as load path requirements, anchorage requirements at truss-to-structure connections and information related to permanent building overall stability bracing that may affect the truss designs, such as shear blocking and drag truss locations. The truss-to-structure connections may be specified by a pre-engineered product, or the engineer of record may allow a substitution of an alternate design by a registered professional engineer.

If an alternate design is to be performed by another registered professional engineer, the Building Designer must specify the loads that the connections are to be designed to resist as well as the direction of these loads.

The owner’s representatives, which can include the engineer of record along with the architect of record and the general contractor, are responsible for reviewing all submittals and coordinating the cold-formed steel submittal drawings in a

delegated design situation with those of all other trades, such as window, mechanical equipment and metal panel drawings, and informing all parties involved of any potential coordination issues in a timely fashion.

permanent individual truss member restraint, and/or individual truss member reinforcement.

A PE seal and signature shall be provided where required by the building designer or the authority having jurisdiction over the project.

Key Responsibilities of the CFS Specialty Engineer

Conclusion In summary, the answer to the age-old question “Who is responsible for what?” remains “Good communication”. It is hoped that this Code of Standard Practice helps clarify just how the flow of communication should go in a CFS framing project and which responsibilities fall to which party in the project.▪

ADVERTISEMENT - For Advertiser Information, visit www.STRUCTUREmag.org

If the design of the CFS framing is contractually delegated to a specialty engineer, this is commonly called either a “performance specification” or “delegated design”. First and foremost, the CFS Specialty Engineer must follow the general intent of the architect and engineer of record. While the CFS Specialty Engineer may be more experienced in the design of CFS framing, they cannot alter the design intent as presented by the Building Designer, who is expecting loads and connections to be transferred to the parts of the structure they are designing at the locations and in the manner that they indicate in the contract documents.

The CFS Specialty Engineer must notify the Building Designer of discrepancies in the contract documents discovered during their work in delegated design. They must get clear direction, usually through the RFI process, before proceeding with a design under their own assumption.

The CFS Specialty Engineer, component manufacturer and/or installer must have at least 14 days to incorporate design changes called for in the A/E review process. The COSP calls for change orders when these required design changes were not part of the original contract drawings.

Key Responsibilities of the CFS Truss Designer CFS Truss designer is a subset of the CFS Specialty Engineer. All provisions noted above must be followed; additionally, there are requirements that are specific to the pre-engineered, pre-fabricated component truss industry.

When the CFS Specialty Engineer is designing trusses, the truss submittal package typically includes: truss design drawings, a truss placement diagram, a cover/truss index sheet, permanent individual truss member bracing, and other structural details germane to the trusses. Upon request by the Building Designer, the truss submittal package may also contain the loads and load combinations used, truss member forces and design assumptions. The individual truss design drawings must include the applicable building code, span, slope, spacing, bearing location, design load, reactions, member and connection information, member forces, deflection information, truss-to-truss connections, STRUCTURE magazine

Jeffrey M. Klaiman, P.E. is a Principal at ADTEK Engineers, Inc. with over 20 years of experience specializing in coldformed steel framing. He also participates in multiple committees of the American Iron & Steel Institute, Light Gauge Steel Engineers Association, ASTM and the Steel Framing Alliance. Mr. Klaiman is currently President of the Mid-Atlantic Steel Framing Alliance (MASFA) and a Past-President of the Cold-Formed Steel Engineers Institute (CFSEI). He can be reached at jklaiman@adtekengineers.com.

55

March 2013

discussion of legal issues of interest to structural engineers

LegaL PersPectives

Scope of Services 101

By Alfred Zarlengo

Y

ou wouldn’t go to your dentist for oral surgery without asking exactly what procedures he or she will be performing and what it will cost, would you? Unfortunately,, this is exactly the trap that many architectural and engineering consultants fall into – neglecting to provide a specific list of services that they will perform as part of their contract.

Outlining your scope of services is important to helping reduce professional liability and risk, as well as boosting your bottom line. To avoid surprises, it is important to nail down exactly what you are going to do, including a list of additional services you recommend and services you will not do, as part of the overall contract negotiation.

2) Additional services you can perform for an additional fee 3) Recommended services you will not perform per the client’s refusal 4) Required services that will be performed by a third party, such as the contractor or subconsultants.

The fourth item – required services performed by others – is often overlooked but very important to spell out. As the prime consultant on a project, you can be liable for failing to ensure a required service was performed up to standard, even if you were not contracted to provide that service directly.

This is true even if the third party performing the services enters into a contract directly with the client.

Sample Scope of Services

Stop Scope Creep Early To recognize scope creep or work not included in the contract, a good rule of thumb is to provide weekly progress reports showing the client what is being accomplished on a project. Using this tool helps catch scope creep early, enabling you and your client to go back and add that scope of work as an addendum and agree on an additional fee for the service.

Unfortunately, those consultants who delay remedying the situation early find themselves and their clients at odds.

Managing a client’s expectations is critical in maintaining a good working relationship over time.

Outlining the Scope of Services Take time to itemize all of the services required to meet the client’s project objectives. Be specific in what services you will be offering. For example, a design firm might perform an initial architectural rendering to give the client a conceptual idea, but additional documents that require specs on sewer and power lines, and other items will be charged separately.

Your goal is to develop a final scope of services that clearly sets forth: 1) Services that you will perform for the agreed-to fee

A useful tool to reach agreement on a reasonable scope of services is a checklist. You can use the basic services listed in the standard American Institute of Architects (AIA) or Engineers Joint Contract Documents Committee (EJCDC) agreement as a starting point, and then customize it to fit your own practice. Services can be listed by project phase.

For example, an architect might categorize services as pre-design, schematic design, design development, construction documents, bidding/negotiation, construction-phase/observation and postconstruction. The following checklist is adapted from the Coalition of American Structural Engineers (CASE): 1) Pre-design Phase – a timeline and number of site visits expected.

2) Schematic Design Phase – structural criteria for geographical studies and systems.

3) Design Development Phase – may include preliminary framing, layout and structural drawings.

4) Contract Document – assist in establishing testing and inspection requirements.

5) Construction Administration – respond to building department and peer review comments Reviewing this checklist with the client prior to signing the contract will go a long

STRUCTURE magazine

57

March 2013

way in providing full disclosure and managing expectations.

Incorporating Scope into the Contract The easiest way to incorporate the scope into your contract is to formalize the checklist as an addendum or exhibit added to the contract, with an appropriate reference within the body of the contract.

A separate addendum should be prepared to itemize what you consider to be critical services you offered to perform but that will be performed by others or will not be performed at all. Note in your contract that you offered to perform these services but the client declined to utilize your services in these areas.

Try to include an indemnity clause that holds you harmless from any damages, liabilities or costs arising out of or connected to you not providing these services. If you are unable to get the client to agree to a formal indemnity agreement, note in your contract that you assume no responsibility to perform any services not specifically listed in your scope of services.

Arming yourself with a basic scope of services checklist will help better prepare you to ask the right questions to negotiate a contract that meets everyone’s expectations, helps to reduce professional liability, and increases your fee.▪ Alfred Zarlengo is an Account Executive in the Professional Liability department at Van Gilder Insurance Corporation, a privately held insurance brokerage firm. Zarlengo specializes in design professionals and environmental consultants, and is a member of the Professional Liability Agents Network (PLAN), which contributed information for this article. Alfred may be reached at azarlengo@vgic.com.

A similar article was submitted by Mr. Zarlengo and appeared in the McGraw Hill’s ENR Mountain States Daily Journal.

Keep your professional license as mobile as you are.

To practice in multiple states, professional engineers need their licenses to be mobile.

NCEES records are recognized by licensing boards nationwide. Once established, your records can quickly and easily be transmitted to any state board to simplify and expedite your application for comity licensure.

You don’t have time for unnecessary paperwork.

Let NCEES keep track of your record so you can focus on what’s ahead.

ncees.org/records records@ncees.org 800–250–3196

business issues

Business Practices

How Long Do I Need To Keep My Records?

G. Daniel Bradshaw, CPCU

A

s an insurance agent working with design firms every day, the new year often begins with phone calls from my engineer clients asking me about document retention. Many of these firms still maintain paper project files along with electronic copies, and some may have part of the project file stored electronically and part in paper form. Firms began to digitize drawings and files years ago, but they often have several years of old drawings and project files stored in their offices. Their question always is: “How long do I have to keep these records?”

Let’s back up for a minute and think about why we are keeping old project records and drawings in the first place. You may have found it handy to archive drawings and records for certain projects to assist clients with future remodeling of their facilities. Those records may now be from very old projects. The other major reason you keep records and drawings is to assist your organization in the event of a dispute on a past project. A complete set of project documents can support or explain your position during a dispute by verifying the scope of your work, your client’s expectations about a project, and the quality assurance/quality control measures that were in place. Documents that accurately reflect the status of a project, the commitments or obligations of the parties, mutual expectations, changes in schedule or cost, or any owner-directed changes become very important.

Keep in mind that, as these documents get added to the project records, they should be clearly written without editorial comment and should memorialize key events and milestones and particular circumstances that led to important decisions. Your documents should consist of facts, not opinions. They should not be ambiguous, or contain admissions of fault or liability or unprofessional personal attacks.

In our current digital world, emails that get added to the electronic record may be long threads of various “cc’s” and reply emails. To make issues clear, it is often better to start a new project email recapping subjects and directing those emails to specific key people working on an issue, rather than “reply to all.”

Tom Bongi, an attorney and the Managing Director of Professional Lines at Catlin Insurance Inc., in a webinar on October 31, 2012, stated each engineering firm should develop a document retention policy. He said this can be accomplished easily in several steps: 1) Survey the firm’s business practices, 2) Consult the firms insurance and accounting advisors, 3) Consult an attorney who can advise on issues for retention during disputes, and on laws of your jurisdiction concerning statutes of repose and statutes of limitations.

A document retention policy communicated to all staff helps to make sure the right kind of information gets preserved. This policy can lay out a systematic plan for reviewing, maintaining and destroying documents and data, including hard copy and electronic documents, databases and emails.

As you establish your policy for document retention, you should consult a local attorney or another knowledgeable expert in your locale to determine the specifics of the statutes of limitation or statutes of

STRUCTURE magazine

repose in your state. These statutes protect you from a claim being made long after a project is completed. These statutes vary from state to state, with time frames running from 6 to 15 years, and their length of time can also change frequently.

When firms understand why they are keeping their paper or digital project records, it makes it easier to create a document retention policy. Such a policy helps engineers keep in mind what makes for good documents should they need to be relied on at some point in the future. The policy also sets the time frame for document retention, and determines when firms can dispose of records. Documents with the necessary factual elements can be invaluable when they are retrieved in the future to assist a client with a remodel or to help a design firm resolve disputes and litigation.▪

59

G. Daniel Bradshaw, CPCU is a professional liability specialist in Bountiful, Utah, and is Immediate Past President of the Professional Liability Agents Network (PLAN), an association of agencies and brokerages serving design firms in the U.S., Canada and Puerto Rico.

Dan may be contacted at Dan@Benchmark-Insurance.com.

This material is provided for informational purposes only. Before taking any action that could have legal or other important consequences, confer with a qualified professional who can provide guidance that considers your own unique circumstances.

March 2013

ADVERTISEMENT

Plugging Analysis Plugging Analysisand andDesign Design into Your 3D Workflow

W

ITH new processes like BIM (Building Information Modeling) and new project delivery methods like IPD (Integrated Project being asked to participate in collaborative, modelMigrating to these new processes can be made easier with software designed to support them— software like Scia Engineer from Nemetschek.

Scia Engineer is a new breed of integrated structural design software that goes beyond

Scia Engineer, update our model, run a quick analysis, and give them enough information to continue moving forward. I don’t think we would have been able to do this with any of the other Another advantage of Scia Engineer is its extensive functionality. Analysis and design is becoming more rigorous, and owners are looking for highly optimized structures to minimize materials, construction time, and costs. Being

Go Beyond Analysis Explore. Optimize. Collaborate.

ability to handle complex analysis tasks is a

Modeling is an essential requirement for any 3D project timelines compressed, modeling needs Engineers need to be able to keep up with the modern designs coming from architects and contractors who push the limits of new materials and methods.

“A unique feature of Scia Engineer is its modeling capabilities,” says Mark Flamer, M.I. FEA (Finite Element Analysis) modeling tool. freeform modeling capabilities make it easy for me to work up designs in 3D and keep pace with my architect’s avant-garde designs. And, its parametric object technology has allowed me to automate routine and repetitive work. I can quickly work up and test design concepts. an accurate structural model in Scia Engineer or link my design to another modeling program for coordination and documentation.”

With support for open standards like IFC 2x3 and direct links to a number of BIM software programs like Autodesk Revit® Structure & Tekla® Structures, Scia Engineer makes it easier for engineers to reuse models created by others advantage when working in a collaborative “For the new National Music Centre project in Calgary, Canada, the architect made frequent and sometimes dramatic changes,” says Andrea Hektor, KPFF Portland. “We needed to be able to give them a quick thumbs up or thumbs down on their revised designs. With Scia Engineer it updated models. We would import them into

“With support for non-linear, multi-material design and multiple codes, I’ve avoided having to invest in disparate analysis programs,” says Michael Ajomale, Principal, Design Depictions Structural Engineering, P.C. “Reducing the number of analysis programs we manage saves on maintenance costs and makes it less expensive to train new employees. Most importantly, it reduces the risks that come with manually coordinating multiple analysis models. For occasions when I need to go outside Scia Engineer, I appreciate its ability to integrate my Excel™ checks and its XML support.”

“More in tune with the “Eye-opening” “Extremely impressed”

Growing with Technology their usual projects, and take on work wherever as well as go beyond buildings,” says Flamer.

“While our expertise is in commercial, we just completed a bridge project and are ready to take He added: “I evaluated the usual list of structural analysis programs, and there isn’t another program in the market like it. Scia Engineer is the only program I found that multi-material design, and lets me easily reuse and share 3D models. For us, Scia Engineer was a logical choice.”

For information, call 1.877.808.Scia (7242) or visit www.nemetschek-engineering.com Daniel Monaghan is the U.S. Managing Director of Nemetschek Scia, developers of leading software products for AEC software industry. He can be reached at dmonaghan@scia-online.com

Read the AECbytes Review

http://nemetschek-scia.com/review

Scia Engineer is a new breed of integrated structural design software that goes beyond

and simple FEA analysis. Recycle and leverage models created by others into analysis. Centralize your design tasks with static, dynamic, and advanced nonlinear analysis, plus mult-material design in ONE program.

Call to request your FREE trial today at (877) 808-7242.

www.nemetschek-scia.com

notable structural engineers

Great achievements

Frank Osborn Nation’s Pioneer Stadium Designer

By Richard G. Weingardt, P.E., Dist.M.ASCE, F. ACEC

A

lthough mostly known as a world-class designer and builder of innovative steel bridges when he founded his consulting engineering firm in 1892, it was not long before Frank Chittenden Osborn (Figure 1) greatly expanded his practice to include the design of a wide array of structures, not the least of them being large-scale sports facilities. By the beginning of the 20th century, his company’s reputation for engineering such structures was so stellar that Osborn Engineering was known as “stadium designers for the nation.”

One of the firm’s most conspicuous stadiums, nearing completion at the time of his death, was the original Yankee Stadium (Figure 2) in New York City, which debuted in 1922 and soon acquired the nickname, “the house that Ruth built.”

In addition to this New York icon, early Osborn-designed Major League Baseball stadiums included Forbes Field, Pittsburgh (1909); League Park, Cleveland (1910); Comiskey Park, Chicago (1910); GriffithNational Park, Washington, DC (1911); Fenway Park, Boston (1912); Tiger-Navin Field, Detroit (1912); and Braves Field, Boston (1915). Also engineered by Osborn’s group, with Henry Herts as architect, was the 1911 Polo Grounds in New York, the sixth concrete and steel stadium built for the Majors (and the second in the National League behind Forbes Field). In addition to being home to baseball’s New York Giants, the stadium’s large number of spectator-friendly outfield seats also made it well-suited for

football games, including nine of the annual Army-Navy contests (Figure 3) between 1913 and 1927.

In 2007, when Frank and his son Kenneth were both inducted into the exclusive Alumni Hall of Fame of Rensselaer Polytechnic Institute (RPI) at the same time, spokesperson Jeff Schanz said, “They were entrepreneurs, innovators, opportunity-recognizers, risktakers and outstanding engineers. Their experience in structural steel and concrete enabled major cities and colleges alike to provide modern, safe stadiums for a new era of professional and collegiate athletics. They’re an inspiration to us all, and their legacy of excellence shines brightly on every Rensselaer student and alumnus.”

Born on December 18, 1857, in Maple Grove, Michigan, in the northwestern section of the state where it fronts Lake Superior, Frank was the middle son of Reuben and Livonia (Chittenden) Osborn. His father Reuben was senior physician for the Calumet and Hecla Mining Company and a prominent member of the Calumet, Michigan community, serving terms as town clerk and as treasurer – and also as a leading school official for thirty years. He was vice-president of the Merchants and Miners Bank of Calumet and director of Farmdale Land and Livestock Company. In the late 1870s, while his son Frank was in college at RPI in Troy, New York, Reuben served as an influential Michigan state senator.

Frank entered Rensselaer in September 1876 after graduating with high marks

Figure 2: Original Yankee Stadium. Courtesy of BuickCenturyDriver/Wikipedia.

STRUCTURE magazine

from Calumet High School. At RPI, he met and quickly befriended George Ferris (1859-1896), Figure 1: Frank C. Osborn. Courtesy of a bright, daring and Men of Ohio in 1900, self-assured 17-year- Benesch Publishing. old from Carson City, Nevada. Although more than a year apart in age and raised in vastly different styles and parts of the country, Frank and George had much in common. For one, both were active in the Chi Phi fraternity and the Pi Eta Scientific Society. In fact, they were enthusiastic founders of Chi Phi at RPI, attracting a Theta chapter there in 1878. The Osborns, like the Ferrises, arrived in America in the early 1600s, and both families qualified as Sons and Daughters of the American Revolution blue bloods. Early in their careers, the two RPI graduates were found working for the same companies and living in the same cities. Later in their careers, both had thriving engineering businesses only 115 miles apart, Osborn in Cleveland and Ferris in Pittsburgh.

Immediately after receiving his civil engineering degree from RPI in the spring of 1880, Osborn entered the service of the Louisville Bridge and Iron Company in Louisville, Kentucky, as assistant engineer. Four months later and just before his marriage on October 27, 1880 to Annie Paull in Calumet, he was advanced to principal assistant engineer with more responsibilities. The Osborns would have two sons, the younger of whom died at birth.

Their older son, Kenneth Howard Osborn

Figure 3: Army-Navy football game at Polo Grounds. Courtesy of Library of Congress Prints and Photographs ppmsca.19488.

61

March 2013

Figure 4: Postcard of Central Bridge, Ohio River at Cincinnati. Courtesy of Peggy W. Holiday Collection.

(1886-1949), would follow in his father’s footsteps and study civil engineering at RPI. After graduating and working briefly for a couple of other engineering organizations, Kenneth joined his father in his flourishing consulting business. Before long, he would become heavily involved in the firm’s expanding stadium design practice and be responsible for many of its high-profile projects.

In 1885, a year before Kenneth was born, Osborn left Louisville Bridge and Iron to become principal assistant engineer with Keystone Bridge Company in Pittsburgh, Pennsylvania, a steel building company founded in 1865 by Andrew Carnegie, the world’s second-richest man. Two years later, in 1887, Osborn was working for and a principal in Ferris’s flourishing engineering firm, G. W. G. Ferris and Company, headquartered in Pittsburgh.

As a leading member of Ferris’s company, which specialized in the inspection and design of major structural steel works around the country, Osborn was mentor and role model to many of the newly hired young RPI-educated engineers employed by Ferris.

Included was William Gronau (1866-1924), a fast-learning engineer who would one day be the lead analyst for the giant, history-making wheel Ferris would build for the 1893 Columbian Exposition in Chicago. Osborn trained young Gronau so well that when Osborn left the firm in 1889, Gronau took his place as the engineer “in charge of design of bridge work.”

Osborn left Ferris to become chief engineer for the King Bridge Company in Cleveland, one of the country’s most rapidly emerging large bridge builders. The King Company had just won the bid to build the Central Bridge over the Ohio River (Figure 4) near Cincinnati, Ohio, a Ferris Company-designed structure. One of Osborn’s first assignments with King was to complete the detailed shop drawings for the bridge, then supervise its construction. Once the project was completed, Osborn was ready to move on.

In 1892, 34-year-old Osborn founded Osborn Engineering Company based in Cleveland.

Initially established to design and consult on all ADVERTISEMENT - For Advertiser Information, visit www.STRUCTUREmag.org

STRUCTURE magazine

62

March 2013

Figure 5: Notre Dame Stadium. Courtesy of Wikimedia Commons/Pgp688.

types of major structural steel projects, the firm quickly became experts in the use of reinforced concrete as a major construction element. With the nation sinking into the throes of a great recession initiated by the worldwide Panic of 1892, it was a testy time to be establishing a new company. However, Osborn boldly went ahead with his plans. At the start, what allowed him to survive was his ability to diversify and engineer a wide array of project types using different structural materials and systems. His pioneering work with reinforced concrete, in particular, coincided with the rapid replacement of fire-prone wooden sports stadiums with fire-resistive structures.

Among Osborn’s early consulting projects were numerous bridges for cities and counties,

the forerunner to today’s popular AISC Steel Construction Manual.

Richard G. Weingardt, D.Sc. (h.c.), P.E., After Osborn passed away on January 31, 1922 Dist.M.ASCE, F. ACEC is the Chairman in Cleveland, Ohio at age 64, his son Kenneth of Richard Weingardt Consultants, Inc. in continued in leadership at the firm until his Denver, CO. He is the author of ten books, death in 1949. By then, Osborn Engineering’s including Circles in the Sky: The Life and bulging portfolio of noteworthy sports faciliTimes of George Ferris and Engineering ties included numerous college stadiums for Legends. His latest book, Empire Man, is several of the nation’s football powerhouses like about Homer Balcom, structural engineer Michigan, Notre Dame (Figure 5), Purdue, for the Empire State Building. He can be and the U. S. Military Academy at West Point. reached at rweingardt@weingarddt.com.

Today, the Osborn firm remains the oldest engiTAY24253 BraceYrslfStrctrMag.qxd 9/3/09 10:09 AM Page 1 neering company in Cleveland.▪

Y O U B U I L D I T. W E ’ L L P R O T E C T I T.

SEISMIC PROTECTION FROM TAYLOR DEVICES Stand firm. Don’t settle for less than the seismic protection of Taylor Fluid Viscous Dampers. As a world leader in the science of shock isolation, we are the team you want between your structure and the undeniable forces of nature. Others agree. Taylor Fluid Viscous Dampers are currently providing earthquake, wind, and motion protection on more than 240 buildings and bridges.

From the historic Los Angeles City Hall to Mexico’s Torre Mayor and the new Shin-Yokohama High-speed Train Station in Japan, owners, architects, engineers, and contractors trust the proven technology of Taylor Devices’ Fluid Viscous Dampers.

ADVERTISEMENT - For Advertiser Information, visit www.STRUCTUREmag.org

plus sundry railroads scattered around the country. Of particular note was the Y-bridge over the Licking and Muskingum rivers at Zanesville, Ohio, which upon its debut was the largest reinforced concrete bridge in the United States. It was labeled the Y-bridge because in plan it formed the shape of the letter Y; its roadway split into two at the mid-span of the river in such a way that one fork of the bridge when crossed was still on the same side of the river from which one started. Another unique Osborn-built bridge was over the Maumee River at Toledo, Ohio.

It featured seven large reinforced concrete arches, together with a 200-foot-long steel bascule span.

In addition to innovative bridges, Osborn engineered countless state-ofthe-art steel frames and roof trusses in conjunction with architects for large buildings, armories, hotels and other facilities. Of note were nine Portland cement plants with a producing capacity of 17,000 barrels of cement a day, a dazzling feat at the time. Also completed

by Osborn’s company was a sprawling complex containing several buildings for the Firestone Tire and Rubber Company at Akron, Ohio. Noteworthy Cleveland buildings were the Union Club, Public Hall, Music Hall and Gray’s Armory.

Professionally, Osborn was active in several technical societies including ASCE, the Institution of Civil Engineers of Great Britain, ASTM, Cleveland Engineering Society and American Railway Bridge and Building Association. In the Civil Engineer’s Club of Cleveland, he was a director, secretary, vice-president and president. He was on the management board of the Association of Engineering Societies and, for three years (1901-03), was a national director of ASCE. He also served several years on the Cuyahoga County Building Commission.

His non-engineering activities included being a director of the Lake Shore Banking and Savings Company and a vice president of the American Art Stone Company.

He was also active in the Cleveland Chamber of Commerce, Masonic Club, University Club, Cleveland Athletic Club and Chippewa Club.

Osborn was the author of the popular engineering handbook Osborn’s Tables of Moments of Inertia and Squares of Radii of Gyration, which featured working strengths of steel members, timber beams and columns, and standard loads, unit stresses and constants for a variety of structures. The book quickly became a much-used industry text,

Taylor Devices’ Fluid Viscous Dampers give you the seismic protection you need and the architectural freedom you want. w w w. t a y l o r d e v i c e s . c o m

North Tonawanda, NY 14120 - 0748 Phone: 716.694 .0800 • Fax: 716.695 .6015

Brace YourselfMarch Magazine October 2009 STRUCTURE TAY24253 magazine 2013 63 Ad Structure

Half-Page Island 5" x 7.5"

Software UpdateS AceCad Software Inc.

Phone: 610-280-9840 Email: m.connolly@strucad.com Web: www.acecadsoftware.com Product: BIMReview Description: A collaborative review and visual communication tool from design to the construction site. Import BIM models and associated data from multiple CAD authoring tools and instantly access project information. Features: Clash checks; Search & edit attribute data; Advanced visualization & CAD tools; Add Attachments & Annotations; 4D planning.

ADAPT Corporation

Phone: 650-306-2400 Email: info@adaptsoft.com Web: www.adaptsoft.com Product: ADAPT-Edge Concrete Building Design Description: Edge extends the Builder software suite to offer the industry’s first truly integrated structural analysis and design solution for concrete buildings using one model. Now slabs, foundations, and vertical elements can be designed without the need to maintain multiple models, saving time and eliminating tedious data duplication.

American Wood Council

Phone: 202-463-2766 Email: info@awc.org Web: www.awc.org Product: Online Connection Calculator Description: A web-based approach to calculating capacities for single bolts, nails, lag screws and wood screws per the 2005 NDS. Both lateral (single and double shear) and withdrawal capacities can be determined. Wood-to-wood, wood-to-concrete, and wood-to-steel connections are possible.

APA – The Engineered Wood Association Phone: 253-565-6600 Email: Marilyn.Thompson@apawood.org Web: www.apawood.org Product: APACAD.org Description: Houses more than 250 CAD details available for free download in four file formats: DWG, DWF, DXF and PDF. All details are adapted from APA’s most frequently used publications and can be searched by title or by product/construction system categories, such as Panel Roof Construction or I-Joist Framing.

CADRE Analytic

Phone: 425-392-4309 Email: cadresales@cadreanalytic.com Web: www.cadreanalytic.com Product: CADRE Geo Description: Geodesic design application for generating a wide variety of geodesic and spherical models for CAD or FEA applications. Output are clean DXF files suitable for structural analysis applications. Also produces detail design data for domes such as hub and pan layouts, dimensions, dihedral angles, volume, surface area.

news and information from software vendors

Product: CADRE Pro 6 Description: Finite element structural analysis application for Windows. Solves beam and/or plate type structures for loads, stresses, displacements, vibration modes. Contains advanced features for stability, buckling, dynamic, shock and seismic analyses. Eleven element types including 9 specialized beams and plates. New features include one-way boundary nodes and forced dynamic response analyses.

CMC Steel Products

Phone: 972-772-0769 Email: marketing@cmc.com Web: www.cmcsteelproducts.com Product: RAM SBeam CMC SMARTBEAM® Version 5.01 Description: A powerful and versatile program for the design of castellated and cellular steel beams.

Using one of several design codes, RAM SBeam – CMC SMARTBEAM® can select the optimum SMARTBEAM size or check the adequacy of existing construction.

Computers & Structures, Inc.

Phone: 510-649-2200 Email: info@csiberkeley.com Web: www.csiberkeley.com Product: CSiBridge Description: Enhanced bridge design of prestressed concrete box girders and composite sections with precast I-girders and U-girders. Design includes the effect of both mild reinforcing and prestress tendons, and is current with the latest US, Eurocode, and International standards. Steel bridge design now includes new steel shapes.

Concrete Masonry Association of CA and NV (CMACN)

Phone: 916-722-1700 Email: info@cmacn.org Web: www.cmacn.org Product: CMD09 Description: Structural design of reinforced concrete or clay hollow unit masonry elements. Designs masonry elements in accordance with Ch. 21 of the 1997 UBC; 2001, 2007 or 2010 CBC; 2003, 2006 or 2009 IBC; and 1999, 2002, 2005 or 2008 Bldg. Code Requirements for Masonry Structures (TMS 402/ACI 530/ASCE 5) [MSJC].

CSC Inc.

Phone: 877-710-2053 Email: sales@cscworld.com Web: www.cscworld.com Product: Tedds Description: With Tedds 2013 you can now analyze frames, use a library of Eurocode and BS design calculations, create high quality documentation and even write your own calculations – all within a single software package.

Download a free trial copy at the website.

STRUCTURE magazine

64

March 2013

Product: Fastrak Description: Dedicated software to automate the design and drafting of steel buildings. Design simple and complex buildings to U.S. codes and then export models directly into Autodesk® Revit®.

Design Data

Phone: 402-441-4000 Email: marnett@sds2.com Web: www.sds2connect.com Product: SDS/2 Connect Description: Enables structural engineers using Autodesk® Revit® Structure to intelligently design connections and produce detailed documentation on those connections. The only product that enables structural engineers to design and communicate connections based on their Revit Structure design model as an active part of the fabrication process.

Devco Software, Inc.

Phone: 541-426-5713 Email: rob@devcosoftware.com Web: www.devcosoftware.com Product: LGBEAMER v8 Description: Analyze and design cold-formed cee, channel and zee sections. Uniform, concentrated, partial span and axial loads. Single and multi-member designs. 2007 NASPEC (2009 IBC) compliant. ProTools include shearwalls, framed openings, X-braces, joists and rafters.

Digital Canal

Phone: 800-449-5033 Email: clint@digitalcanal.com Web: www.digitalcanal.com Product: Wind Analysis, Concrete Beam, and Pile Cap Description: Digital Canal’s most recent software updates include: Wind Analysis (ASCE 7-10 and 7-05), Concrete Beam design (ACI 318-2011) and Pile Cap design (ACI 318-2005). Additionally, the time proven and easy to use SES Software Suite has been compliance tested for Windows 8. For free downloads visit the website.

Dlubal Engineering Software

Phone: +49 (0) 9673/9203-0 Email: info@dlubal.com Web: www.dlubal.com Product: RSTAB and RFEM Description: Powerful tool to calculate 3D models consisting of steel, reinforced concrete, timber, aluminum or glass. Possible to define members, plates, shells and solids. BIM planning is possible due to numerous interfaces. Demo version available.

All Resource Guides and Updates for the 2013 Editorial Calendar are now available on the website, www.STRUCTUREmag.org. Listings are provided as a courtesy. STRUCTURE® magazine is not responsible for errors.

news and information from software vendors

ENERCALC, INC.

ENERCALC

Phone: 800-424-2252 Email: info@enercalc.com Web: www.enercalc.com Product: RetainPro 10 Description: The latest release of this widely used retaining wall & earth retention software package.

Cantilevered, restrained, gravity, gabion, sheet pile and segmental wall design modules are provided. Up to current code provisions this ever evolving and full featured program has been serving the industry for 20+ years.

Product: Structural Engineering Library Description: Full suite of programs for design & analysis of building components. This widely used package enables engineers to create sets of calculations for all common tasks. Comprehensive, flexible licensing, continual enhancements and celebrating our 30th year serving the industry.

Visit the website for complete information and to download an evaluation.

Product: VAConnect Description: Steel connection design just got easier!

Integrates with IES VisualAnalysis. VAConnect tools also run stand-alone. With IES Transparent Reporting™ you get reports that look like you wrote them by hand with sketches, equations, and code references. These tools are the opposite of black-box and blind-trust.

King & Associates LLC

Phone: 866-739-5464 Email: rex@spacegass.com Web: www.spacegass.com Product: SPACE GASS 11 Description: A major new version that includes a stunning new 3D renderer with full editing capabilities plus other major new features such as on-screen notes, job attachments, dimensions, load combinations grid, measure tool, textures, gridlines, new shape builder and animated moving loads. Large displacement theory has been added.

LARSA, Inc.

GT STRUDL

Phone: 404-894-2260 Email: casec@ce.gatech.edu Web: www.gtstrudl.gatech.edu Product: GT STRUDL V32 Description: Comprehensive linear and nonlinear static and dynamic analysis features for frame and finite element structures. Models plastic hinges, geometric nonlinearities, discrete dampers, tension/compression only members and nonlinear connections. Steel Design including NEW Nuclear Codes and Reinforced Concrete Design. Base Plate Analysis and Multi-Processor Solvers are available.

Hilti, Inc.

Phone: 800-707-0816 Email: sales@iesweb.com Web: www.iesweb.com Product: VisualAnalysis Description: You have many choices for FEA, but VisualAnalysis stands alone: Quick for everyday projects. Easy to use; friendly support. Three levels to suite your needs. Versatile: model just about anything.

Reports are beautiful and flexible. 3000 customers: just one support person…think about it!

Phone: 800-LARSA-01 Email: info@larsa4d.com Web: www.Larsa4D.com Product: LARSA 4D Description: Analysis and design software addressing the specialized needs for bridges and structures including “4D” time effects. With features such as performing pushover, progressive collapse, and nonlinear time history within staged analysis, LARSA 4D has become the standard in leading U.S. firms for design, construction, and seismic analysis.

Leigh & OKane, LLC

Phone: 816-916-6950 Email: Rokane@leok.com Web: www.Leok.com Product: RWallHD Description: This iPad app provides the user with complete control of all input with a real time dynamic graphical response. It allows the user to optimize the design of concrete retaining walls within minutes. Files can be saved, previewed, and emailed for printing. Optional surcharge loads, sloped backfill, and shear key.

Phone: 573-446-3221 Email: info@mdxsoftware.com Web: www.mdxsoftware.com Product: Curved and Straight Steel Bridge Design and Rating Software Description: Curved and straight steel girder bridge design and rating software according to AASHTO LRFD, LRFR, LFD, and ASD specs.

Nemetschek Scia

Phone: 877-808-7242 Email: info@scia-online.com Web: www.nemetschek-scia.com Product: Scia Engineer Description: Looking to migrate to, or improve your 3D design workflows? Scia Engineer links structural modeling, analysis, design, drawings, and reports in ONE program. Design to multiple codes. Tackle larger projects with advanced non-linear and dynamic analysis. Plug into BIM with IFC support, and bidirectional links to Revit, Tekla, and programs.

Opti-Mate, Inc.

Phone: 610-530-9031 Email: optimate@enter.net Web: www.opti-mate.com Product: Bridge Software Description: Software titles include Merlin Dash for steel and concrete girders, Descus I and II for curved I and box girders, TRAP for trusses and SABRE for sign bridges.

Pile Dynamics, Inc.

Phone: 216-831-6131 Email: www.info@pile.com Web: www.pile.com/pdi Product: GRLWEAP Software Program Description: Wave Equation Analysis of Piles: simulates pile driving, predicts driving stresses, hammer performance, the relation between bearing capacity and net set per blow and total driving time. Helps select job-adequate hammers. 800+ preprogrammed hammers, several analysis options. Offshore Piles version available.

Codes may allow leaner design with GRLWEAP analysis.

continued on next page

SOILSTRUCTURE.COM

Mad Software, Inc.

Phone: 303-564-2318 Email: ghoback@madsoftware.net Web: www.madsoftware.net Product: AxisVM Description: Structural modeling, design, and analysis for concrete, steel, timber structures with BIM interchange capacity. ACI, AISC, NDS, Eurocodes and other design codes supported.

Plate, beam, shell and membrane elements plus special elements. Since 1991.

STRUCTURE magazine

MDX Software

1.

2.

3.

4.

5.

Substructural Software Soldier Pile/Wood Lagging Multi-Level Tieback Walls Laterally Loaded Drilled Pier Anchored or Cant. Sheetpile Cantilever Retaining Wall

Only $280 to $450. Nothing to ship.

Same Day Email Activation

Free Downloads at: http://www.SoilStructure.com

65

March 2013

ADVERTISEMENT - For Advertiser Information, visit www.STRUCTUREmag.org

Phone: 800-879-8000 Email: us-sales@hilti.com Web: www.us.hilti.com Product: PROFIS Anchor and PROFIS DF Description: Hilti offers two design programs for structural engineers. PROFIS Anchor performs anchor design for cast-in-place and Hilti post-installed anchors using ACI 318, Appendix D provisions.

PROFIS DF Diaphragm performs design calculations for steel deck roof and floor diaphragms using the SDI Diaphragm Design Manual, 3rd Edition provisions.

IES, Inc.

Software UpdateS

Software UpdateS PopIcon Software

Phone: 415-875-7850 Email: communications@popiconsoftware.com Web: www.popiconsoftware.com Product: PopIcon for Revit 2013 Description: A plug in that works with Revit 2013, Revit Architecture, and Revit Structure to bring families to your fingertips with icon-based, easy-to-use menus and customizable features.

POSTEN Engineering Systems

Phone: 510-275-4750 Email: sales@postensoft.com Web: www.postensoft.com Product: POSTEN Multistory V9 Description: The most powerful, comprehensive & efficient post-tensioned concrete design software is ready for Windows 8 (32 & 64 bit) with advanced design procedures that actually Design the tendons & drapes for you (no fiddling or time wasting) with Sustainable Design algorithms that provide documentation for LEED with the Efficient design.

Powers Fasteners

Phone: 985-807-6666 Email: jzenor@powers.com Web: www.powers.com Product: Powers Design Assist Software 2.0 Description: Software to design to ACI 318 Appendix D.

RISA Technologies

Phone: 949-951-5815 Email: info@risatech.com Web: www.risa.com Product: RISAConnection Description: The cutting edge of next-generation connection design software. Featuring full 3D visualization, Shop-drawing – style views, and expandable engineering calculations for all limit states, RISAConnection is an essential tool for engineers who use steel. Its complete integration with RISA-3D and RISAFloor allow one-click connection design for entire structures.

S-FRAME Software Inc.

Phone: 203-421-4800 Email: info@s-frame.com Web: www.s-frame.com Product: S-FRAME® Analysis Description: An easy-to-use structural modeling and analysis environment for bridges, frames, trusses, office and residential high-rises, industrial buildings, plate/shell structures, and cable structures for seismic analysis, staged construction, slab design, Direct Analysis Method, linear and nonlinear static and time history analyses, moving load analysis, buckling load evaluation and more.

news and information from software vendors

Simpson Strong-Tie

Phone: 800-999-5099 Email: web@strongtie.com Web: www.strongtie.com Product: Simpson Strong-Tie® Strong Frame® Moment Frame Selector Software Description: Strong Frame selector software helps designers select an ordinary or special moment frame for their project’s given geometry and loading. With minimum input geometries, the software narrows down available stock frames to a handful of possible solutions. For opening dimensions outside of stock frame sizes, the selector provides possible customized solutions.

Standards Design Group Inc.

Phone: 806-792-5086 Email: Info@standardsdesign.com Web: www.standardsdesign.com Product: Window Glass Design 5 Description: Performs all required calculations to design window glass according to ASTM E 1300-09.

This software also performs window glass design using ASTM E 1300 02/03/04, ASTM E 1300-98/00 and ASTM E 1300-94.

Product: Wind Loads on Stuctures 4 Description: Performs all the wind load computations in ASCE 7-98, 02 or 05, Section 6 and ASCE 7-10, Chapters 26-31. It allows the user to “build” structures within the system, provides basic wind speeds from a built-in version of the wind speed map(s) or allows the user to enter.

Strand7 Pty Ltd

Phone: 252-504-2282 Email: anne@beaufort-analysis.com Web: www.strand7.com Product: Strand7 Description: An advanced, general purpose, FEA system used worldwide by engineers, designers, and analysts for a wide range of structural analysis applications. It comprises preprocessing, solvers (linear and nonlinear static and dynamic capabilities) and postprocessing. Features include staged construction, quasi-static solver for shrinkage and creep/relaxation problems.

StructurePoint

Phone: 847-966-4357 Email: info@structurepoint.org Web: www.StructurePoint.org Product: Concrete Design Software Description: Upgraded to ACI 318-11, PCA’s concrete design suite is now: spSlab, spColumn, spMats, spWall, spBeam & spFrame. Formerly pcaSlab, pcaWall, pcaMats, pcaColumn, pcaBeam and pcaFrame, our programs are widely used for analysis, design and investigation of reinforced concrete buildings, bridges and structures.

STRUCTURE magazine

66

March 2013

Struware, LLC

Phone: 904-302-6724 Email: email@struware.com Web: www.struware.com Product: Struware Code Search Description: Struware announces a new update of its Code Search program. The program will provide you with all pertinent wind, seismic, snow, live and dead loads in just minutes. The software incorporates ASCE 7-98 thru 10 and all versions of the IBC. Struware also offers other structural software. Demos at website.

USP Structural Connectors

Phone: 800-328-5934 Email: info@uspconnectors.com Web: www.uspconnectors.com Product: USP Specifier v1.1 Description: Users can design beam-to-joist type hangers, input load requirements, and generate connector schedules that can easily be input into CAD drawings. USP Specifier also lets users define product lists, group connectors by project, print pick list reports, and compare USP’s products alongside its competitors’ offerings.

Weyerhaeuser

Phone: 888-453-8358 Email: wood@weyerhaeuser.com Web: www.woodbywy.com Product: Javelin Structural Frame Modeling and Design Software Description: Specification, detailing and analysis of wood framing for roofs, walls and floors. 3D BIM tools model the structural frame and produce member calculations, framing layouts and material lists. v5.0 makes it easy to develop and track loads for compression roof systems using rafters, ridge boards, hips and valleys.

WoodWorks Software

Phone: 800-844-1275 Email: sales@woodworks-software.com Web: www.woodworks-software.com Product: WoodWorks® Design Office Suite Description: Includes 3 programs: SHEARWALLS: designs perforated and segmented shearwalls; generates loads; rigid and flexible diaphragm distribution methods. SIZER: designs beams, columns, studs, joists up to 6 spans; automatic load patterning.

CONNECTIONS: Wood to: wood, steel or concrete.

New Version available March 2013!

All Resource Guides and Updates for the 2013 Editorial Calendar are now available on the website, www.STRUCTUREmag.org. Listings are provided as a courtesy. STRUCTURE® magazine is not responsible for errors.

Design wood structures effectively, economically and with ease!

Design Office Suite includes 3 programs:

Sizer • Designs beams, columns, studs and joists

(light frame, heavy timber, glulam and engineered lumber) • Allows eccentric axial loads and combined axial and lateral loads for up to 100 loads using any distribution (point, trapezoidal, partial uniform, etc.)

• Designs sloped and oblique angled beams up to 6 spans

Shearwalls

Most buildings can be modelled in minutes. Shearwalls then generates wind and seismic loads, distributes forces to shearwalls using rigid and flexible diaphragm methods, and designs perforated and full height segment shearwalls.

Free training videos available on our website!

Connections

Designs connections using lag screws, bolts, wood screws, nails, rivets and shear plates

AMERICAN WOOD COUNCIL

US Design Offie 9 also includes: Editable Database, NDS 2005 (PDF) and SDPWS 2008 (PDF)

CDN Design Office 8 also includes: Editable Database and CSA-O86-09 (PDF)

US Design Office 10 - Coming this Spring NDS 2012, IBC 2012 and ASCE 07-10 compliant

Download a Free Demo at woodworks-software.com www.woodworks-software.com

800-844-1275

March 26, 2013 –

N IO AT UC

ST

UIN

G

NCSEA IN

Craig E. Barnes, P.E., SECB is principal and founder of CBI Consulting Inc. As an engineer registered in both the civil and structural fields, Mr. Barnes has over 40 years experience designing, coordinating, and managing structural and civil engineering projects throughout New England.

RS

RU

CT

UR

AL

ASCE 7-10: Wind Loads on Non-Standard Building Configurations Don Scott, P.E., S.E., PCS Structural Solutions ASCE 7-10 wind load provisions are written for “Regular-Shaped Buildings”, however these provisions are applied every day to “Non-Regular Buildings”. What techniques are applied to use the information in the standard for non-regular buildings? When can and should you use the ASCE 7-10 provisions or look for guidance in other standards?

This webinar will present answers to these questions.

EE

News form the National Council of Structural Engineers Associations

Wind Tunnel Applications for Buildings Jim Swanson & Jon Galsworthy Code prescribed analytical procedures for calculation of wind loads may not accurately predict the response of very tall or irreguJim Swanson, lar buildings to the actual load conditions S.E., P.E., they will experience. Wind tunnel testing is Halvorson & offered as an alternative to these procedures Partners for situations where more reliable load and response consideration is necessary to evaluate the building’s performance. This course will present a complete summary of the wind tunnel testing procedures from a user’s perspective. Topics to be covered include code Jon Galsworthy, requirements, testing options, test reports, response thresholds, and adjustments for Ph.D., P.Eng, RWDI improved performance.

GIN

NCSEA News

March 12, 2013 –

EN

A “good” Structural Engineer, a Structural Engineer with a passion for Structural Engineering, becomes a “good” mentor without even knowing it. Perhaps a coworker will suggest they like the way you explain something. Perhaps you coach your son or daughter’s hockey team and parents marvel at the eagerness with which their kids respond to your coaching. Perhaps, over dinner, you monopolize the conversation with little Johnny as you describe your day’s activities, until your spouse says, “Yes dear, now give little Johnny a chance to describe his school day”. Becoming a good mentor can happen as naturally and imperceptibly as becoming an experienced Structural Engineer.

It is a growth process, although I firmly believe the term “mentor – proficienair” (a term I’ve coined to describe someone who is extremely good at what they do) is reserved for the most passionate of Structural Engineers.

Now that you have become one, think about the process. How did you get there? Having earned that exalted title, you look to your trophy case and realize there is still an open space beside the high school hockey trophy. There are no trophies, there are no awards for good mentors, but there is immense satisfaction as you see newbies grow and flower.

Were you the prodigy of a good mentor? Did that individual spend selfless time leading you through the challenges of becoming a Structural Engineer? Did that individual invite you to join him or her in professional development opportunities? Did that individual not only encourage you to take specific continuing education courses but make it a requirement of advancement in the firm? Perhaps as a young engineer you were like the sole practitioner. As the sole practitioner you needed to rely on self-teaching, self-development, and extremely important, self appreciation. Which one were you?

Now, as a firm Principal or a good senior Structural Engineer, look about you. Pick out those that you believe can become good mentors. Find a way within the firm to encourage them to take on the mentoring role. Mentor the mentors.

Give it a try. You’ll like it.

NT

O NS

STRUCTU

OCIATI

COUNCI L

March NCSEA Webinars

CO

ASS

NATIONAL

“The Mentor”

ED

GINEERS

RAL

EN

Diamond Reviewed

SPECIAL OFFER for the Wind Series! Buy four webinars, get the fifth FREE! The offer includes live or recorded webinars, or a combination thereof for the Wind Series. These courses will award 1.5 hours of

continuing education. Approved for CE credit in all 50 States through the NCSEA Diamond Review Program.

Time: 10:00 AM Pacific, 11:00 AM Mountain, 12:00 PM Central, 1:00 PM Eastern. Register at www.ncsea.com.

Mark Your Calendars!

2013 NCSEA Annual Conference September 18-21 Join NCSEA on LinkedIn! Connect with fellow structural engineers through NCSEA’s LinkedIn group at www.linkedin.com.

Westin Buckhead Hotel, Atlanta, Georgia More information coming soon at www.ncsea.com STRUCTURE magazine

68

March 2013

OCIATI

O NS

COUNCI L

NATIONAL

ASS

RAL

News from the National Council of Structural Engineers Associations

STRUCTU

NCSEA News

March 2013

69

STRUCTURE magazine

GINEERS

EN

The Newsletter of the Structural Engineering Institute of ASCE

Structural Columns

Structures 2013 Conference Registration Now Open Make your plans to attend the Structures 2013 Congress in Pittsburgh, PA, May 2 – 4, 2013. The focus of this highly regarded specialty conference is Bridging Your Passion with Your Profession. The ASCE/SEI Structures Congress is your annual opportunity to broaden your technical knowledge, sharpen your business skills, deepen your understanding of cutting-edge research, and network with your peers and colleagues. There will be eleven technical tracks covering a wide range of structural engineering topics including; buildings, bridges, blast, innovative engineering, seismic, reinforced concrete, and business practice.

For more information or to register, visit the congress website at www.structurescongress.org/.

Special Student and Young Professional Events at Structures 2013 Congress For Students and Young Professionals, the Structures 2013 Congress includes special programs of events designed for you to make the most of your Congress experience and to help keep you involved with SEI.

Featured Events for Young Professionals: • Soft Skills for the Young Engineer • Meet the Leaders Breakfast • Young Professional Luncheon Featured Student Events: • Career Launch 2013 • Student Welcome and Firm Tour • Student Structural Design Competition See the complete list at www.structurescongress.org/. Tickets are required for most events, please follow the detailed registration instructions on the Congress website when you register at www.structurescongress.org.

For more information on these sessions and to see the complete matrix of Technical Sessions, visit the Congress website at http://content.asce.org/conferences/structures2013/.

Errata SEI posts up-to-date errata information for our publications at www.asce.org/SEI. Click on “Publications” on our menu, and select “Errata.” If you have any errata that you would like to submit, please email it to Paul Sgambati at psgambati@asce.org.

Local Activities Welcome to the first official SEI Graduate Student Chapter (GSC) at Virginia Tech chaired by William Collins wncollins@vt.edu and Faculty Advisor Roberto Leon rleon@vt.edu.

The mission of the SEI-VT GSC is to develop the leadership skills and enhance the education of students who are preparing to become structural engineering professionals. By linking SEI student members with professional members, and providing opportunities for professional and educational development, SEI-VT will facilitate a successful college to career transition.

SEI-VT will engage student members in SEI to encourage active, continuous membership and involvement throughout their professional lives. SEI-VT will provide a series of speakers from the structural engineering industry that will focus on professional issues related to the industry. Educational and technical seminars and webinars will also be organized to enhance the educational experience of SEI-VT student members. Engagement will be encouraged through SEI-VT sponsored activities and outreach opportunities, as well as by the development of relationships with professional SEI members.

The New Orleans Chapter recently held two seminars for local members. Their next seminar will be on the topic of litigations and how to avoid them. SEI New Orleans Chapter STRUCTURE magazine

70

has invited Jeffrey Coleman, P.E. (Coleman, Hull & Van Villet, Minneapolis, MN) who will present Learning from the Past, Structural Problems that Ended in Litigation on February 26. Mr. Coleman will state a few actual cases and the lessons learned from those project cases.

The Kansas City Chapter recently hosted Dr. Patrick J Fortney, P.E., P.Eng and Dr. William Thornton, P.E. of Cives Engineering Corporation to present on seismic connection design. The local membership came away with new knowledge on the seismic design of connections and economic decisions to be considered.

The chapter hopes the success and rave reviews of this meeting carries over to the February gathering, a roundtable on the SE licensure efforts in MO and KS. SEI-KC and SEAKM-KC will pair together to gather members of the Missouri Board, NCEES, and the SE licensure effort to inform the membership on the current situation.

To get involved with the events and activities of your local SEI Chapter or Structural Technical Group (STG), visit http://content.seinstitute.org/committees/local.html. Local groups offer a variety of opportunities for professional development, student and community outreach, mentoring, scholarships, networking, and technical tours.

March 2013

Celebrate Great Bridges If you love bridges, we want your photos! ASCE will recognize 13 winners and 25 finalists from a variety of categories.

Winning photos are eligible for inclusion in ASCE’s 2014 Bridges Calendar. Contest closes on March 31, 2013. Enter today!

myLearning Your New PDH Tracker and Personalized Hub for Continuing Education

SEI was proud to present the 2012 Gene Wilhoite Award in Transmission Line Engineering to Otto J. Lynch, P.E., M. ASCE. This award is presented to an individual for significant contributions to the advancement of the art and science of transmission line engineering. Mr. Lynch received his B.S. in Civil Engineering from the University of Missouri at Rolla in 1988 and is Vice President of PLSi. He has designed lines from 69kV to 500kV around the world and was the pioneer in the use of LiDAR in the transmission line industry. He is a member of the National Electrical Safety Code and is active on many ASCE and IEEE committees.

The Gene Wilhoite Award was presented to Mr. Lynch by Bob Nickerson, Chair of the Wilhoite Award Committee, during the Opening Plenary Session of the Electrical Transmission and Substation Structures Conference, November 5, 2012 in Columbus, Ohio.

For a summary of the entire conference see the SEI website at www.asce.org/SEI.

New ASCE Structural Webinars Available SEI partners with ASCE Continuing Education to present quality live interactive webinars on useful topics in structural engineering. Several new webinars are available:

Structural Building Condition Surveys: Looking for Trouble ASCE 7-10 Snow Load Provisions An Introduction to ASCE 7-10 Wind Loads – Part II Aging Infrastructure, Risks, and Making Tough Decisions Design of Reinforced Concrete Liquid Structures

March 4, 2013 March 6, 2013 March 8, 2013 March 11, 2013 March 13, 2013

An Introduction to ASCE 7-10 Wind Loads – Part III Design Loads on Structures during Construction Using ASCE 37 Significant Changes to the General Requirements for Determining Wind Loads of ASCE 7-10

March 15, 2013 March 22, 2013 March 27, 2013

Webinars are live interactive learning experiences. All you need is a computer with high-speed internet access and a phone. These events feature an expert speaker on practice-oriented technical and management topics relevant to civil engineers.

Pay a single site fee and provide training for an unlimited number of engineers at that site for one low fee, and no cost or lost time for travel and lodging. ASCE’s experienced instructors STRUCTURE magazine

James A. D’Aloisio Michael O’Rourke Bill Coulbourne Ehsan Minaie Leonel (Leo) Almanzar & Paul F. Blomberg Bill Coulbourne Bill Coulbourne Eric Stafford

deliver the training to your location, with minimal disruption in workflow – ideal for brown-bag lunch training.

ASCE Webinars are completed in a short amount of time – generally 60 to 90 minutes – and staff can earn one or more PDHs for each Webinar.

Visit the ASCE Continuing Education Website for more details and to register at www.asce.org/conted.

71

March 2013

The Newsletter of the Structural Engineering Institute of ASCE

Manage your professional development and license renewal through ASCE’s new learning management system – myLearning. Track all your PDHs/CEUs, including those from other providers; obtain certificates of completion; take program-related exams; print or save transcripts of your professional development – all in one place! Make myLearning your personalized hub for continuing education and explore the comprehensive program catalog and track your PDHs. Visit the myLearning website at www.asce.org/mylearning/ and get started today.

Wilhoite Award Presented at ETS Conference

Structural Columns

ASCE Bridges Photo Contest

Top Industry and Government Leaders, Political Programs, Teaming Fair to Highlight

CASE in Point

The Newsletter of the Council of American Structural Engineers

ACEC 2013 Convention April 21–24 Business and politics are the focus of the upcoming ACEC 2013 Annual Convention and Legislative Summit in Washington, D.C., April 21-24.

MWH Global Chairman/CEO Alan Krause, URS President Gary Jandegian, and AECOM North America Chief Executive

Michael Della Rocca will discuss Major Projects and Alternative Delivery Systems in a general session.

The future of QBS will be addressed by Bill Mielke, president & CEO, Ruekert/Mielke, Inc.; Jim Horrocks, president, Horrocks Engineers, Inc.; and Robert Boyer, vice president, CH2M HILL. NBC News Chief White House Correspondent Chuck Todd will head up a blue-chip slate of political speakers.

The Convention will also feature Capitol Hill visits; legislative updates and projections; federal market opportunities; CEO, CFO and CIO roundtables; bottom-line focused educational sessions; the Engineering Excellence Awards Gala; and a “teaming fair” for large and small firms to pursue partnering opportunities.

Go to www.acec.org/conferences/annual-13/index.cfm for more information and to register!

Join CASE! The Council of American Structural Engineers (CASE) is a national association of structural engineering firms that provides a forum for action to improve the business of structural engineering. This is achieved through implementation of best practices, reduced professional liability exposure and increased profitability.

Your membership gets you free access to contracts covering various situations, as well as access guidance on AIA documents, national guidelines for the structural engineer

Donate To The CASE Scholarship Fund!

We have all witnessed the stiff competition from other disciplines and professions eager to obtain the best and brightest young talent from a dwindling pool of engineering graduates.

One way to enhance the ability of students in pursuing their dreams to become professional engineers is to offer incentives in educational support.

The ACEC Council of American Structural Engineers (CASE) is currently seeking contributions to continue making the structural engineering scholarship program a success. The CASE scholarship, administered by the ACEC College of Fellows, is awarded to a student seeking a Bachelor’s degree, at minimum, in an ABET-accredited engineering program.

Your monetary support is vital in helping CASE and ACEC increase scholarships to those students who are the future of our industry. You don’t have to be an ACEC member to donate!

Contact Heather Talbert at htalbert@acec.org to donate.

STRUCTURE magazine

72

of record, free access to tools designed on how to reduce risk within your firm, two CASE convocations dedicated to Best Practice structural engineering, AND free downloads of all CASE documents 24/7.

For more information, go to www.acec.org/case or contact Heather Talbert at htalbert@acec.org. You must be an ACEC member to join CASE. You can follow ACEC Coalitions on Twitter–@ACECCoalitions.

New Commentary on the 2010 Code of Standard Practice Now Available!

CASE 976-C, A Review and Commentary of the American Institute of Steel Construction 2010 Code of Standard Practice for Steel Buildings and Bridges discusses the list of changes published in the preface of the 2010 Edition and provides some commentary to these changes. This document also addresses areas of the COSP that may not be well understood by some SERs, but will likely have an impact on the structural engineer’s practice of designing and specifying structural steel.

The 2010 COSP addresses many recent changes in the practice of designing, purchasing, fabricating and erecting structural steel, and is therefore a continuation of the trend of past improvements and developments of this standard.

Developed by the CASE Guidelines Committee, the commentary is available at www.booksforengineers.com.

March 2013

Updated CASE Contract Now Available!

Looking for publications focused on structural engineering?

Now is the time to purchase these valuable resources, written by structural engineers for structural engineers, at a 20% discount!

CASE products are built on the years of combined experience and know-how of its members. CASE is dedicated to improving the quality of the structural engineering industry through enhanced business practices, decreased professional liability exposure and increased profitability. Take advantage of this discount and see your business improve its bottom line.

Sale ends March 31, 2013. Go to www.booksforengineers.com to take advantage now!

CASE Contract #11: An Agreement between Structural Engineer of Record (SER) and Contractor for the Transfer of Digital Data (Computer Aided Drafting (CAD) or Building Information Model (BIM)) Files© was recently updated by the CASE Contracts Committee. The sample contract provides an agreement for the SER to use when transferring digital data (CAD or BMA) files to the contractor. Items include: Agreement Form, with a description of files; and Agreement Terms and Conditions. The updated contract is available at www.booksforengineers.com.

If you would like more information on the items below, please contact Ed Bajer, ebajer@acec.org.

Ethics in Texas

Defining the Undefinable

The Texas Engineering Practice Act contains a section on ethics, §137.63. Here is an excerpt of what the engineer can’t do – (1) aid or abet, directly or indirectly, any unlicensed person or business entity in the unlawful practice of engineering; (2) maliciously injure or attempt to injure or damage the personal or professional reputation of another by any means. This does not preclude an engineer from giving a frank but private appraisal of engineers or other persons or firms when requested by a client or prospective employer; (3) retaliate against a person who provides reference material for an application for a license or who in good faith attempts to bring forward an allegation of wrongdoing; (4) give, offer or promise to pay or deliver, directly or indirectly, any commission, gift, favor, gratuity, benefit, or reward as an inducement to secure any specific engineering work or assignment; (5) accept compensation or benefits from more than one party for services pertaining to the same project or assignment; or (6) solicit professional employment in any false or misleading advertising.

The dictionary defines “intangible” as something incapable of being defined. However, the U.S. 9th Circuit Court of Appeals has awarded $28.8 million in damages for “intangible environmental harm” against a contractor in California. Following a fire in the Angeles National Forest caused from sparks from a project nearby, the federal government sued for harm to wildlife habitats, soil, plants, loss of recreational use, scenic views and a historic mining camp. The intangible harm became tangible at about $1600 per acre of 18,000 acres of burned forest.

STRUCTURE magazine

Services Prior to Signing a Contract Many professionals do this, and not only in the engineering profession. It may be to show the client that you are serious and eager to get started on their project. Some insurance policies may make reference to the time when services are rendered but a formal agreement is not signed. You should know what your policy says. In any event, you may want to write a letter of commitment as you understand your role in that time period; it may encourage the execution of a formal agreement.

73

March 2013

CASE is a part of the American Council of Engineering Companies

CASE Business Practice Corner

CASE in Point

Save 20% in March on all CASE Products

Structural Forum

opinions on topics of current importance to structural engineers

Engineers and the Public Good

By Ashvin A. Shah, P.E., F. ASCE “The civil engineering profession recognizes the reality of limited natural resources, the desire for sustainable practices (including life-cycle analysis and sustainable design techniques), and the need for social equity in the consumption of resources.” This quote from ASCE Policy Statement 418, The Role of the Civil Engineer in Sustainable Development, links the issue of environmental sustainability with that of social equity.

These two concerns are not easily tackled separately from each other or by one nation independently of the rest of the world. Yet that is exactly what is happening today: scientists addressing the long-term issue of environmental sustainability without simultaneously recognizing its short-term impact on the economy, and economists addressing the short-term issue of unemployment without simultaneously recognizing the long-term need for an environmentally sustainable global economy.

Thomas Brooks, writing in this space (August 2012), sees the global link of economies as follows: “American businesses outsourcing and offshoring jobs to India and China” so as “to remain competitive” is one reason “hindering a full recovery” of the American economy. The less restrictive labor and environmental laws abroad constitute the primary reason for outsourcing American jobs. It is a short-sighted solution that creates social inequity across the board, causing unemployment in the United States and facilitating slave shops in Asian countries, as well as environmental degradation across the board, as rich and poor alike in Asia choke in pollution that eventually drifts to the U.S. West Coast.

“So what’s the solution?” asks the editor of Modern Steel Construction (October 2011). He adds, “I believe that we need to start taking responsibility for the products we purchase.

However, the solution can’t rest on the actions of individuals as that would unfairly penalize those who try to do the right thing. Instead, we need a national policy that imposes tariffs on imported products that do not meet our environmental and labor regulations.” The global macro-economists who support free movement of capital across national boundaries would regard this as too nationalistic and

protectionist; it would likely result in trade wars and hurt both economies.

Fortunately, after the near-collapse of Wall Street in 2008, economists have undergone soul-searching about the fundamental assumptions of their discipline. They now recognize that in addition to capital resources, two other key inputs also deserve their attention: labor, including skilled labor and technologies, and natural resources. Labor injects the social equity issue into the economy, and natural resources inject the environmental sustainability issue. Recently, there has emerged a new international group of economists focusing on these two issues. They held their first annual conference in 2008 in Paris, and the most recent one in 2012 in Montreal.

Climate scientists and environmentalists approach sustainability with a global perspective, but generally do not get involved in the social equity issue, choosing to remain close to their field. Engineers, on the other hand, need to be concerned about social equity as they work directly with manual and skilled labor. Much has been written on the topic of the differences between scientists and engineers in their approaches to problem-solving. Henry Petroski, in his book, The Essential Engineer: Why Science Alone Will Not Solve Our Global Problems, invokes C. P. Snow’s reference long ago to the cultural divide between the humanities and sciences, then explains as follows a similar cultural divide between scientists and engineers: If the two cultures of a half century ago were the sciences and the humanities, are the two cultures of today the sciences and engineering? Do scientists understand engineering, and vice versa? ... But the overall cultures of the sciences and engineering can be as disparate as those that Snow observed between the sciences and humanities.

While there are scientists who look down on engineering and engineers who dismiss science as of no practical value, in an age of apparent climate change and other global issues, it is incumbent upon both cultures to see the importance of the other in

defining and solving the problems of the planet ... We all should strive to be of one culture ... There can be little doubt that these are not times for the global scientific, engineering, economic, political, and public policy communities to separate themselves into competing cultures. They can best unite when they understand each other’s disciplines and their essential roles in contributing to the whole.

After a century of technological progress and rationalization of markets, we now have three cultures – scientists, economists, and engineers – that interact in making decisions about global economic issues involving science and technology. In his bimonthly InFocus columns in this publication, Jon Schmidt has written extensively on social captivities of the engineering profession and is now developing virtue ethics concepts that could help engineers deal with the moral issue of the public good. For example, his column on “Knowledge, Rationality, and Judgment” (July 2012) explains the three traits that are all too often pursued singly by scientists, economists, and engineers, respectively, when what is needed is a fusion of these dispositions.

In the meantime, social equity and environmental sustainability are addressed in ASCE Policy 418, which states that “ASCE will work on a global scale” for engineers to “have a role in planning, designing, building and ensuring a sustainable future. Engineers provide the bridge between science and society. In this role, engineers must actively promote and participate in multidisciplinary teams with other professionals, such as ecologists, economists, and sociologists to effectively address the issues and challenges of sustainable development.”▪ Ashvin A. Shah, P.E., F. ASCE (ashvinshah@aol.com), is a professional engineer in Scarsdale, New York. He is involved in the topics of clean energy technologies, social equity, and environmental sustainability in the global economy.

Structural Forum is intended to stimulate thoughtful dialogue and debate among structural engineers and other participants in the design and construction process. Any opinions expressed in Structural Forum are those of the author(s) and do not necessarily reflect the views of NCSEA, CASE, SEI, C 3 Ink, or the STRUCTURE® magazine Editorial Board.

STRUCTURE magazine

74

March 2013

NASCC BOOTH 725

An Essential Link in Your Structural Model RISAConnection represents the cutting edge of next-generation connection design software. Its complete integration with RISA-3D and RISAFloor allow one-click connection design for your entire structure. Featuring full 3D visualization, shop–drawing–style views and expandable engineering calculations for all limit states, RISAConnection is an essential tool for engineers who design steel.

www.risa.com

800.332.RISA

© 2013 RISA Technologies, LLC