STRUCTURE magazine | May 2014

May 2014 Masonry

A Joint Publication of NCSEA | CASE | SEI

STRUCTURE ®

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FEATURES 22

The Sky is Falling! No, It’s Marble!

Guastavino Masonry Shells

By John Ochsendorf, Ph.D.

COLUMNS 7 Editorial Mentoring: It Makes Good Sense

By Thomas A. Grogan, Jr., P.E., S.E. and Heather Anesta, P.E.

9 InFocus Rationality and Judgment Revisited

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

In the late 19 th and early 20 th centuries, the Guastavino Company designed and built some of the most exceptional masonry structures in history by adapting a traditional Mediterranean vaulting method. Read about these vaulting methods and structural achievements, calculation approaches for masonry vaults, and the potential for Guastavino-style vaults to be built in the future.

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May 2014

By Stephen H. Getz

Failing anchors in marble ceiling panels at the Fairmont Memorial Mausoleum in Newark, New Jersey, limit access for ceremonies and visiting patrons. Constructed in the 1920s, the mausoleum was not conditioned for climate, and nine decades of changing weather has challenged both the stone durability and anchorage connections.

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CONTENTS

11 Guest Column MasonrySystems.org (MSO)

By Tim O’Toole

14 Construction Issues Bracing Masonry Walls under Construction Using Their Own Strength

By Diane Throop, P.E. and Scott Walkowicz, P.E.

Tensioning Masonry to New Heights

18 Structural Design

By Kelly Robertson, P.E. and Paul Scott, P.E., S.E.

Armory Park in Tucson, Arizona, is the tallest post-tensioned masonry building in the United States. Completed in 2013, the new building is six stories high and encompasses 139,000 square feet. After an evaluation of the relative cost, schedule impacts, and LEED requirements, a posttensioned system was chosen to be used as the exterior wall.

Brick Curtainwall for Essential Buildings

By John G. Tawresey S.E.

35 Engineer’s Notebook Flexural Masonry

By Jerod G. Johnson, Ph.D., S.E.

DEPARTMENTS

A Joint Publication of NCSEA | CASE | SEI

Advertiser Index InBox Noteworthy Bookcase Resource Guide (Steel/CFS) 44 NCSEA News 46 SEI Structural Columns 48 CASE in Point

STRUCTURE

8 38 39 39 40

37 InSights

®

IN EVERY ISSUE

ON

THE

COVER

The main staircase of Baker Hall at Carnegie Mellon University is a masterpiece of Guastavino construction, with a 4-inch thick shell of masonry spiraling in three dimensions. This is just one of the projects constructed by the Guastavino Company in the late 19 th and early 20 th centuries.

See feature article on page 26.

May 2014 Masonry

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.

STRUCTURE magazine

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May 2014

Structural Health Monitoring of America’s Infrastructure

By Duncan Paterson, P.E., Ph.D.

43 Spotlight For the Birds: Reimagining a Legacy

By Chris Olson, S.E.

50 Structural Forum Training the Structural Engineer – Part 2

By Stan R. Caldwell, P.E., SECB

Design concrete anchoring connections in minutes!

Truspec is a new and free anchor calculation software allowing Architects and Engineers to design concrete anchoring connections in minutes in accordance with ACI 318 Appendix D. This software includes a user-friendly integrated design and implements real-time 3D graphics, color coded results, and value displays in US Customary or Metric Units. Product datasheet, photos, ICC-ES evaluation reports, and specification packages are all included in the Truspec anchor calculation software.

Truspec anchor calculation software users can quickly and easily: • Create anchor connections in accordance with ACI 318 Appendix D

• Select the number of anchor points

• Model simultaneous moment forces in x-, y-, z-axis

• Predict mode of failure for anchor connections

• Model multiple edge and spacing distance configurations

• Recommend most efficient anchor size

• Calculate critical values for total strength design of anchor connections

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• Optimize designs across multiple scenarios.

• Recommend most efficient anchoring method • Specify anchoring methods to achieve a desired failure mode

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Editorial

Mentoring: It Makes Good Sense

new trends, new techniques and current industry issues

By Thomas A. Grogan, Jr., P.E., S.E. and Heather Anesta, P.E., M.S., LEED AP

As our careers have developed over time, most of us can think back to that special engineer or two that spearheaded our development as structural engineers. That special bond between mentor and mentee began in an informal fashion, and it wasn’t until later in our careers that the value of that relationship was recognized. At NCSEA, we believe relationships like these strengthen the careers of those involved and significantly increase the value of participating in our organization.

A Senior Engineer’s Perspective

A Young Engineer’s Perspective

When I went to college almost 35 years ago, I was told by my high school guidance counselor that my affinity for math and science made me a perfect candidate for engineering. It wasn’t until I took a concrete design class in my junior year of college, however, that I found my true calling.

I have had the opportunity to work for firms with as few as 10 to over 10,000 employees.

Most of the mentoring I received over the years came from my supervisors. I never truly appreciated their efforts, but they helped me develop into a very competent structural engineer.

In my current position, I am regularly involved in ensuring that all of our structural engineers are technically strong. Recently, I added leadership training, including how to hire a good engineer, handle tough employee issues, and perform effective employee evaluations, as well as negotiation skills and effective business writing. We began monthly sessions discussing these skills and, over time, our engineers’ exposure to these concepts improved their performance.

In 2004, I became involved with FSEA, and NCSEA by extension. I was impressed by the educational offerings and networking opportunities provided, and I was exposed to many young engineers, ranging from recent grads to those with up to 15 years experience. When they expressed a need to be mentored (especially from 2007 to 2010 when jobs were few and far between), FSEA responded by creating a young members group; and I had the opportunity to work with these young engineers, offering career and technical advice. They were very talented and eager to learn. I wanted to ensure that strong computer and calculation skills were developed in concert with practical rules of thumb, which are the types of skills that we “more seasoned” engineers bring to the table. I believe it is imperative that we make mentoring part of our DNA. Then, as we pass the baton to the future of this great profession, we can rest assured that these young engineers will take structural engineering to places we never thought possible.

I graduated from Florida State University in December 2007, just prior to the beginning of the economic downturn. Though grateful to be employed, I was cut to part time while our office issued mandatory pay cuts as my firm’s backlog diminished. My boss was my only structural engineering mentor, and now he had much more critical things to focus on than rearing a young engineer. As grim as this appeared, this is the best thing that’s ever happened to me. It put me in touch with both FSEA and NCSEA. I survived 2008-2013 without leaving the structural engineering discipline. I was able to continue my professional and technical growth. I obtained my master’s degree and PE license, and I hope to obtain my SE License in 2014. I could not have done this without my employer and my FSEA and NCSEA mentors.

In 2010, I started a “Young Members Group” (YMG) for FSEA’s Palm Beach (PB) Chapter. I did this because there did not seem to be a place for EIs and recent PEs to obtain continuing education. We were not aware of all the valuable FSEA and NCSEA events available to us.

After only 3 months, the 2011 FSEA PB YMG had over 30 members.

It was clear that there were many EIs and recent PEs other than myself that wanted to devote themselves to becoming competent structural engineers. We met monthly to discuss codes and design techniques.

Local, “more seasoned” PEs presented to us monthly on their specialties, and they became our mentors. They were available to us when we had questions, they checked in with us and forwarded valuable information, and they offered us jobs as the economy improved.

Since then, I have been involved in exposing the rest of the country to the YMG experience through NCSEA, and there are currently more than 38 YMGs as a result. If you are a young engineer or student, find your local NCSEA Member Organization, reach out to its board members, and find your mentor(s)! For those “more seasoned”, please become a mentor because your knowledge and experience is incredibly valuable!

Thomas A. Grogan, Jr., P.E., S.E., is Chief Structural Engineer and Director of Quality at The Haskell Company in Jacksonville, FL. He is also an NCSEA Board member, member of the NCSEA Licensure Committee and past president of FSEA, and a volunteer with ACE Mentorship. Please feel free to reach him via email at thomas.grogan@haskell.com.

Heather Anesta, P.E., M.S., LEED AP, is an Associate Structural Engineer & Project Manager at Stantec, the Chair of the NCSEA YMG Support Committee, Membership Chair for FSEA, and a volunteer with ACE Mentorship. Please feel free to reach her via email at heather.anesta@stantec.com.

The NCSEA YMG Support Committee is now hosting a Mentor Matching Program. The program links together structural engineers of all experience levels and ages based on similar interests. I encourage all of you to visit www.ncsea.com/members/younggroups/ and complete a sign-up form. You can sign up as a Mentor or a Mentee – and there is no age restriction for either option! All we ask is that you “JUST DO IT”.

STRUCTURE magazine

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May 2014

Advertiser index

PleAse suPPort these Advertisers

American Concrete Institute ................. 25 Bentley Systems, Inc. ............................. 51 CTP, Inc................................................ 23 Design Data .......................................... 42 Enercalc, Inc. .......................................... 3 Engineering International, Inc............... 15 Fyfe ....................................................... 19 Halfen, Inc. ............................................. 4

Integrated Engineering Software, Inc..... 34 ITW Red Head ....................................... 6 KPFF Consulting Engineers .................... 8 Powers Fasteners, Inc. .............................. 2 Quikrete ................................................ 10 RISA Technologies ................................ 52 Simpson Strong-Tie............................... 21 Soc. of Naval Arch. & Marine Eng. ....... 38

Editorial Board Chair

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

Brian W. Miller

CBI Consulting, Inc., Boston, MA

AdvErtising Account MAnAgEr Interactive Sales Associates

Jon A. Schmidt, P.E., SECB

Craig E. Barnes, P.E., SECB

Structural Engineers, Inc. ...................... 12 Structural Technologies ......................... 13 StructurePoint ....................................... 36 Struware, Inc. ........................................ 43 Taylor Devices, Inc. ............................... 29 USP Structural Connectors ................... 17 Wood Advisory Services, Inc. ................ 40

Chuck Minor

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Davis, CA

John A. Dal Pino, S.E.

Evans Mountzouris, P.E.

Degenkolb Engineers, San Francisco, CA

The DiSalvo Engineering Group, Ridgefield, CT

Mark W. Holmberg, P.E.

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

Heath & Lineback Engineers, Inc., Marietta, GA

KPFF Consulting Engineers, Seattle, WA

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

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

Khatri International Inc., Pasadena, CA

BergerABAM, Vancouver, WA

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

John “Buddy” Showalter, P.E.

Brian J. Leshko, P.E.

Amy Trygestad, P.E.

CCFSS, Rolla, MO

American Wood Council, Leesburg, VA

HDR Engineering, Inc., Pittsburgh, PA

Chase Engineering, LLC, New Prague, MN

WASHINGTON STATE DEPARTMENT OF INFORMATION SERVICES OLYMPIA, WA

EditoriAL stAFF Executive Editor Jeanne Vogelzang, JD, CAE

execdir@ncsea.com

Editor

Christine M. Sloat, P.E.

publisher@STRUCTUREmag.org

Associate Editor Graphic Designer Web Developer

Nikki Alger

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graphics@STRUCTUREmag.org

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STRUCTURE ® (Volume 21, Number 5). 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 $75/yr domestic; $40/ yr student; $90/yr Canada; $60/yr Canadian student; $135/yr foreign; $90/yr foreign student. For change of address or duplicate copies, contact subscriptions@STRUCTUREmag.org. 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.

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inFocus

Rationality new trends, new techniques andandJudgment current industry issues Revisited

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

I

have written previously about the shift in modern philosophy and culture away from practical judgment (phronesis) in favor of technical rationality (techne), primarily citing the work of Joseph Dunne (“Knowledge, Rationality, and Judgment,” July 2012; “The Rationality of Practice,” September 2012). Recently, I have encountered several other authors who have observed the same trend and called attention to its detrimental impacts on society.

Scott H. Moore, a philosophy professor at Baylor University, specifically references Dunne in a 2011 online paper, “The Rough Ground and the Consolations of Techne” (www.georgetowncollege.edu/cdal/ files/2011/06/scott_moore.pdf). His goal is “to highlight the differences between phronesis and techne and emphasize the necessity of pursuing the difficult prudence of phronesis while resisting the all-inclusive allure of techne.” To that end, Moore provides several delightfully concrete examples: • “It is not merely the existence of these wonderful gadgets … it is the delusory fantasy which many of us entertain that, through technology, we will finally be able to overcome the challenges which we face.”

• “Take for instance the ways in which the easy access to information can corrupt us. When I can always look it up, I have no reason to learn it.”

• “The analysis or critique of work principally becomes the analysis of whether proper procedure was followed.”

• “... one cannot repair one’s marriage in the same way that one repairs one’s computer. There is no single set of rules or skills or formulae which may be used to solve the problems which vex human community.”

David Edward Tabachnick, a political science professor at Nipissing University in North Bay, Ontario, Canada, expresses similar concerns in his 2013 book, The Great Reversal: How We Let Technology Take Control of the Planet. His primary objective is “to provide a history of the changing relationship between the judgmental and technical through an analysis of some of the great texts of political philosophy.”

Tabachnick begins with the ancient Greeks, contrasting Plato’s concept of “kingly techne” with Aristotle’s call for “phronetic rule.”

Augustine subsequently divided practical judgment into “prudence of the flesh,” dealing with earthly matters, and “prudence of the spirit,” addressing religious life. Thomas Aquinas later added a divinely informed conscience as a “top-down” guide to doing right, in contrast to the “bottom-up” nature of phronesis. Machiavelli then effectively took both “the good” and God out of the equation, recasting politics as a techne for strong rulers to employ in shaping their realms.

Hobbes completed the transformation, exalting science over fallible human “guesses” and issuing a challenge to find the set of natural laws that presumably govern people’s behavior. The (so-called) Enlightenment that followed sought to “purge any and all irrational elements from everyday life,” leading Kant to divorce judgment from experience and attempt to ground it instead in universal principles.

Meanwhile, the emerging field of statistics provided governments with a new way to measure and predict social and economic developments.

As a result, “instead of good judgment guiding technical knowledge,

STRUCTURE magazine

technical knowledge comes to guide judgment, turning the ancient virtue of phronesis into a subordinate of a larger scientific project to perfect humanity.”

Aldous Huxley’s 1932 novel, Brave New World, may be interpreted as a vision of what the future could look like if this process is taken to its logical (albeit extreme) conclusion. He posits an era when people are mass-produced like any other product and genetically engineered to be perfectly suited for a predetermined role in the new order. Rather than a totalitarian regime maintained by fear and punishment, as in George Orwell’s 1984, Huxley imagines a scenario in which those in power instead simply guarantee everyone’s permanent happiness by turning traditional morality on its head and freely distributing a safe tranquilizing drug. Needless to say, Aristotle’s notion of eudaimonia – genuine well-being or human flourishing – is nowhere to be found.

Tabachnick’s last two chapters survey various responses to the “Great Reversal,” in particular that of Heidegger, and discuss the prospects for a “phronesis revival.” For this to happen, “technical innovation must be directed by the higher virtues such as those associated with family, community, education, politics, and philosophy”; and “technical production has to be preceded by the ethical mastery or self-discipline of the passions.” The chief obstacle is the fact that “[w]e have handed over our decision-making procedures to a range of technical experts, specialists, and managers and have thus left few if any sources for relearning the practice of the virtue.”

Barry Schwartz and Kenneth Sharpe make much the same point in their 2010 book, Practical Wisdom: The Right Way to Do the Right Thing.

They apply recent insights from psychology and cognitive science to validate the core concepts of Aristotelian virtue ethics, drawing reallife examples primarily from doctors, lawyers, and teachers. Constant pressure to focus on health care costs (rather than quality), client advocacy (rather than justice), and standardized test scores (rather than education) have had an adverse effect on these professions. Rules and incentives have become ubiquitous, reducing or even eliminating opportunities for the exercise of discretion, which is essential to the development of good judgment as well as personal satisfaction.

What about engineers? Our codes and standards have become too lengthy and prescriptive. Computerization and globalization threaten to turn our services into a commodity. Managers in many firms urge us to maximize our billable time and attempt to develop policies and procedures that will streamline our “production” efforts. While the work that we do is obviously very technical in nature, it still needs to be governed ultimately by practical judgment if we are to be Virtuous Engineers who strive to enhance the material well-being of all (www.VirtuousEngineers.org).▪ Jon A. Schmidt, P.E., SECB (chair@STRUCTUREmag.org), 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, and shares occasional thoughts at twitter.com/JonAlanSchmidt.

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May 2014

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M

asonrySystems.org is the brainchild of the Masonry Executives Council (MEC), a coalition of professionals from more than two dozen masonry associations. The goal of the website is to provide a unified source of inspiration and information about masonry design and construction. By working together, these associations are striving to make it easier for architects, engineers, developers, school boards, and city officials to choose to use masonry for their buildings.

The site is broken down into seven sections: • Wall Systems • Details • Benefits • Gallery • Knowledge • Communication • Resources Designed to provide a user-friendly experience to visitors, all content can easily be accessed from the site’s unique navigation menu (Figure 1).

“Our overall goal for the MSO website was to create a user-friendly, aesthetically pleasant, and informational website that is used as an industry standard not only for masonry contractors, but also for architects, owners, masonry suppliers, and other interested parties,” said Imani Brodie, Geotechnical & Environmental Products Engineer at Carolina Stalite Company. “With this new design, I do believe we have achieved all of these goals.”

of various masonry wall systems that comply with current codes.

Each wall system page provides detailed diagrams of the system, along with a 3D model that can be downloaded into Trimble’s SketchUp (see Figure 2, page 12, for an example of brick veneer and reinforced CMU). Extensive design tips and considerations have been provided that reference specific codes and standards that apply to the wall system, as well as free downloadable resources.

The site makes it easy for you to determine what building type each wall system is best suited for, along with the benefits of using that specific wall system. But that’s not all; you can find the fire rating, sound transmission class, energy rating, and LEED rating for each system.

What if you don’t know what type of wall system is best for your project? Not to worry!

MasonrySystems.org has you covered there too.

Simply go to the “Help Me Choose” feature, answer a handful of short questions, and the site will provide you with a recommended wall system and alternative wall systems that work for your project.

For example, let’s say you’re the structural engineer working on a museum with a stone exterior. Simply select your building type, life expectancy, and exterior, and you’ll be taken to a page that recommends using a cavity wall with a stone slab veneer and reinforced concrete masonry.

Masonry Wall Systems

Masonry Construction Details

MasonrySystems.org allows visitors to determine which masonry wall system is right for their next building, and learn why masonry structures outlast and outperform every other building system. The site features an extensive selection

The latest and greatest addition to MasonrySystems. org is the Masonry Construction Details section.

Select your state and you’ll be able to view a library of quality masonry construction details. It’s a quick and simple way to access hundreds of free masonry

Guest Column dedicated to the dissemination of information from other organizations

MasonrySystems.org (MSO)

Figure 1. MasonrySystems.org.

STRUCTURE magazine

11

A Resource for Structural Engineers

By Tim O’Toole

Tim O’Toole is the Director of Marketing, Education, and Information Technology for the Mason Contractors Association of America in Algonquin, Illinois and the developer of the MasonrySystems. org website. Tim can be reached at totoole@masoncontractors.org.

Figure 3. United States Federal Building, Tuscaloosa, AL. Courtesy of Stanley Capps.

Figure 2. Brick veneer and reinforced CMU.

details that can be download into your CAD program. From wall sections and control joints to window jambs and flashing, the site has everything and anything you’re looking for.

Benefits of Masonry

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Using a masonry system for your next project will help you deliver a completed, structurally sound building in the shortest period of time. Masonry buildings go up fast and last.

There are a number of significant benefits of masonry, including its performance under fire conditions as well as life safety, costbenefits analysis, and mold. And, the energy saving characteristic of a masonry system wall is second to none.

MasonrySystems.org highlights all of these benefits, and provides dozens of resources including videos, articles and publications that can be downloaded or purchased and used to help get the most out of your next project.

And you won’t want to miss out on the masonry facts. Each time you visit the site, a

new fact about masonry will appear to educate visitors on the many benefits and aspects of masonry. For example, did you know one 8-inch CMU can support 205 sumo wrestlers weighing 500 pounds each? You never know what you might learn when you visit MasonrySystems.org!

Get Inspired Discover the beauty and versatility of brick, block and stone by browsing hundreds of masonry buildings across the country in the Project Gallery (Figure 3).

Projects can be viewed by category: College and University, Commercial Education: 9-12, Education: K-8, Government, Industrial, Institutional, Landscape/Hardscape,

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Figure 4. Masonry Directory.

STRUCTURE magazine

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May 2014

Rehabilitation/Restoration, Residential: MultiFamily and Single Family.

Along with photos showcasing the masonry aspects of the structure, each project features a vast amount of information, including details about the architect, structural engineer, mason contractor and suppliers who worked on the project; an in-depth description of the project highlighting why masonry was selected and the benefits gained from using masonry; and, a direct link to information and details about the wall system used on the project.

There is even a section that allows visitors to submit their own masonry project to be added to the gallery and featured on the site.

Nearly three hundred projects can be viewed in the constantly expanding gallery.

Knowledge Base Do you need engineering information about masonry and need it fast? The Knowledge Base is where you’ll want to navigate.

The knowledge base is the heart and soul of MasonrySystems.org, acting as a clearinghouse of everything masonry. There are apps to use in your browser, free presentations to download, and videos to watch. You’ll be able to view hundreds of resources and barely scratch the surface of all the content that is available.

If you’re unfamiliar with masonry, there’s even a glossary featuring common masonry terms with definitions, photos, and detailed information to help get you up to speed.

Communication Center

Masonry Resource Directory The robust Masonry Directory (Figure 4) allows visitors to search nearly five thousand profiles of mason contractors, general contractors, architects, structural engineers, masonry suppliers, masonry associations and masonry instructors.

Each project includes company contact information, areas of work each company specializes in, and photos of projects the company has worked on.

The Only Masonry Resource You Need Whether you have just a few minutes to find specific information or several hours to browse the hundreds of projects and details housed on the site, MasonrySystems.org will be an excellent resource for every practicing structural engineer.

“I encourage and all but demand that you go check out the site for yourself,” said Brodie. “My hope is that you are both pleasantly surprised and inspired to return to the site in the future.”

We hope that you will visit and read the entire MasonrySystems.org website and hopefully make the decision to “go masonry” on your next project.▪

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Have a question about masonry? Post it in the Communication Center. These interactive, online forums allow visitors to share problems and solutions, and bounce ideas off one another.

Visitors can discuss structural design and performance of masonry wall systems, masonry construction issues, tools and equipment, and logistics. There is a forum for everyone, and a great community of masonry experts ready and willing to share their knowledge.

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ConstruCtion issues discussion of construction issues and techniques

B

racing of masonry walls under construction using the wall’s inherent strength rather than external bracing elements is a newer approach to bracing, and is known as Internal Bracing. It has been successfully applied in numerous projects with short to very tall walls. Bracing, in general, provides life safety for workers and other occupants on the job site, essentially keeping the wall up during construction and long enough to provide time for evacuation during a wind event. Protection of property, including the wall or walls under construction, is not the purpose of the bracing … although additional design considerations (such as utilizing higher or even occupancy design level wind speeds) may lead to bracing effective at accomplishing property protection as well. Internal bracing provides an excellent option to accomplish these goals. The Masonry Contractors Association’s Standard Practice for Bracing Masonry Walls Under Construction (Standard ) provides the basis for design of external or internal masonry wall bracing. An additional guide specific to internal bracing design is the International Masonry Institute’s Internal Bracing Design Guide for Masonry Walls Under Construction (Internal Bracing Guide).

Bracing Masonry Walls under Construction Using Their Own Strength

By Diane Throop, P.E. and Scott Walkowicz, P.E.

The Concept of Internal Bracing Diane Throop, P.E., is Director of Engineering, International Masonry Institute, Annapolis, MD and was Chair of The Masonry Standards Joint Committee for the development of the 2011 and 2013 editions of the Building Code Requirements for Masonry Structures (TMS 402/ACI530/ ASCE5) and Specification for Masonry Structures (TMS602/ ACI530.1/ASCE6). She can be reached at dthroop@imiweb.org.

Scott W. Walkowicz, P.E., heads his own consulting firm, Walkowicz Consulting Engineers located in Lansing, Michigan. He is the President of The Masonry Society (TMS) and is former Chair of the General Requirements Subcommittee for the Masonry Standards Joint Committee (MSJC) – the structural masonry code. He may be reached at scott@walkowiczce.com.

Internal bracing of masonry walls under construction is based on the cantilevered performance of the wall and utilizes predicted capacity to resist defined wind loads that may occur during construction and before the wall’s final lateral support is in place. Internal Bracing provides verifiable engineering capacity and performance similar to, and in many cases better than, systems that incorporate external bracing components. For most masonry capacity calculations, it utilizes reduced design criteria such as lower values for the masonry’s compressive strength, applies lateral loads for specified wind speeds, and provides tangible benefits to the project as described later in this article. Figure 1 shows a cantilevered wall with two base doweling conditions that influence the ability of a wall to perform as internally braced. The center diagram shows a common pinned base condition where the foundation dowel extends only 6 inches into the base of the masonry wall. This condition will provide only minimal capacity before the dowel embedment in the masonry fails and the wall becomes pinned at the base leaving only self-weight to resist over-turning.

The right side diagram shows a wall with a 2.5foot dowel (full development for a #5 bar with

14 May 2014

Figure 1. Cantilevered wall diagrams.

grout cured 24 hours). This wall will develop cantilevered capacity as the grout cures and then the wall performs with base fixity and moment continuity. Make sure the structural reinforcement is sized and spaced properly, and that wall is internally braced!

The Basics Restricted Zone Beyond wall and brace capacity, the other key aspect of masonry bracing is the creation of a Restricted Zone. Because the bracing is typically engineered to resist wind speeds as specified in the Standard, which are lower than those required in the International Building Code, the Restricted Zone protects persons from serious injury or death by defining an area to be evacuated in the event of mandated wind speeds and prior to a partial or complete wall failure.

Initial and Intermediate Periods The under-construction definition can be paraphrased as the entire time between when the masonry is first laid and when the wall’s final lateral support is in place. That time period is broken into two distinct phases: The Initial Period and the Intermediate Period. There are different design requirements and restrictions for each.

Walls are generally considered unbraced in the Initial Period in that only the wall’s self-weight is considered effective in resisting overturning and flexural stresses, since the mortar and grout have not gained sufficient strength to resist load.

The Intermediate Period is defined as being the period of time following the Initial Period until the wall is connected to the elements that provide its final lateral support. That can be interpreted as being the period starting when

the masonry is more than a day old until the wall is connected to a diaphragm or other elements that are sufficiently capable of transferring lateral force from the wall through other elements to the foundation.

Bar joists or beams bearing on, or connected to, the wall may not qualify as ‘final lateral support’. Each project condition should be evaluated independently to determine when the Intermediate Period ends.

Materials Masonry Assemblies

The article mentions two documents specific to masonry bracing – the Standard Practice for Bracing Masonry Walls Under Construction (Standard ) and the Internal Bracing Design Guide for Masonry Walls Under Construction (Internal Bracing Guide).

The Standard is an industry standard prepared by masonry professionals under the voluntary umbrella group called the Council for Masonry Wall Bracing. While not a building code, it is referenced in the current edition of the MSJC and has been used to meet OSHA mandated bracing requirements. As masonry is often site-built, at the time of construction the strength of masonry most likely will be below that assumed while it is in service. So, from a practical point of view, it is impossible to prevent walls under construction from blowing down under some circumstances. (Note that in most cases, the loads imposed during construction are also likely to be less than service loads.) As a result, the Standard is intended to permit masonry construction to continue during low wind speed conditions, but requiring workers to evacuate designated areas of the job under high wind conditions. feet, and design engineers are often open to modifying bar sizes, spacing and even foundation dowel lengths.

Foundation and Soils Foundation analysis and, more specifically, soil capacity analysis can significantly impact the ability to use Internal Bracing. Recognizing that the demand placed on foundations is short term, only during the braced period, allows a more generous foundation evaluation: higher bearing pressures and minor potential rotation are acceptable because property protection is not the primary goal of a bracing scheme. Higher allowable bearing pressures should be utilized, and consideration be given to passive and active pressure for providing resistance to sliding and rotation. Safety factors on bearing pressure are often in the range of 3.0 to 4.0 or higher, so the ultimate bearing capacity of the soil provides much higher capacity for short term loads. A common approach for bracing foundation evaluation is to take the reported allowable bearing capacity, multiply it by 3.0 and then factor it down by some smaller reduction factor, such as 25%, to obtain the design pressure.

Internal Bracing Analysis Initial Period Analysis During the Initial Period, the mortar, and grout where applicable, has not gained sufficient strength to resist load. Walls have only their self-weight available to resist overturning and flexure. As noted above, masonry walls are not considered to be braced during the Initial Period. Therefore, there isn’t bracing engineering to be done – but there are limits that must be met. The Standard contains two provisions: Evacuate the Restricted Zone whenever the wind speed exceeds 20 miles per hour, and the height of masonry

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above the base or highest line of support shall not exceed that shown in tables in the Standard. A bracing plan should incorporate height limits for all new masonry based on the Initial Period requirements.

Intermediate Period Analysis Advantages of internally braced masonry walls become apparent during the intermediate period. Masonry walls can spend a significant amount of time in the Intermediate Period, depending on when diaphragms and the final lateral system are fully implemented.

It’s a good thing that masonry begins gaining strength early, often providing its own support for resisting short term loads even as the construction is on-going. During the Intermediate Period, the Restricted Zone must be evacuated when the wind speed exceeds 35 miles per hour. That evacuation wind speed, coupled with a design wind speed of 40 miles per hour, provides a time and load buffer to facilitate evacuation.

The primary focus of Internal Bracing is bracing to resist wind load during the Intermediate Period. Reinforced masonry analysis for Internal Bracing design can be

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Masonry Assemblies – Reinforced masonry walls are the best candidates for internal bracing. This article focuses on low pour and low lift heights to generate capacity at the base of the cantilevered wall, although there are ways to use internal bracing with high lift and high pour heights or with unreinforced masonry (both the Standard and the Internal Bracing Guide offer guidance). Pour height refers to the masonry wall height that is constructed prior to grout placement. Limiting the ungrouted wall height as the construction progresses by using low-pour heights takes advantage of strength that develops very quickly in constructed masonry and uses that strength, along with connection to the foundation, to internally brace the wall without an external brace system.

Reinforced walls are the best candidates for application of Internal Bracing principles due to the significant strength that the reinforcement can add as the grout cures. If the wall reinforcement is properly doweled to the foundation, base fixity can create the desired cantilevered performance typically within 12 to 24 hours after grout placement. The short term design provisions in the Standard are modeled after those in the Masonry Standards Joint Committee’s Building Code Requirements for Masonry Structures except that compressive stresses or strengths are reduced based on the reduction in masonry compressive strength. Analysis must consider axial and flexural tension and compression, as well as global over-turning. The bracing engineer must know the unit size and properties, unit weight, net area unit compressive strength, and mortar type and placement, and especially the reinforcement bar size and spacing to be used in construction. If the reinforcement shown in the design documents proves insufficient for a cantilevered wall condition, consider increasing reinforcement size and/or decreasing reinforcement spacing.

Reinforced masonry walls have been internally braced for heights in excess of sixty

Standard and Guide

achieved through hand calculations, and spreadsheets or software solutions. Most software packages allow the masonry net area compressive strength to be set by the user so the appropriate value can be entered for the Intermediate Period. Because the steel can be fully developed once the grout has cured for 12 to 24 hours, no change is needed for the tension portion of the analysis. The Internal Bracing Guide provides detailed examples.

Internal bracing design philosophy is based on the masonry code and basic principles of mechanics, so bracing design should start with the reinforcement denoted in the construction drawings. Basic masonry analysis equations found in masonry design texts, such as The Masonry Designer’s Guide, can be used with the modified design values from the Standard.

For example, allowable stress analysis can be conducted using Equation 9.4-11, fb = (2*M)/ (jkbd2), for when masonry compression controls, and Equation 9.4-12, fs = M / (A s jd), for when tension in the reinforcement controls.

Those equations can be re-arranged to solve for moment capacity within the wall, while substituting the proper f'i for fb and the proper elastic modulus for the intermediate period

Figure 2. Bracing plan content. Courtesy of IMI – Internal Bracing Guide.

masonry. Those limiting equations become, respectively: M ≤ f'i * (jkbd2)/2 and M ≤ fsAsjd.

With a little work to find k and j, the analysis can be easily completed. Iteration would be required if different masonry strengths or bar size/spacing values are found to be necessary.

Option to Eliminate Restricted Zones Eliminating the Restricted Zones can be done but requires the use of design level wind speeds and higher lateral pressures. More significant masonry reinforcement and foundations typically result and their cost must be considered when evaluating bracing concepts.

Deliverables: Internal Bracing Plan Once an Internal Bracing scheme has been evaluated and designed, it is important to properly and fully represent that design through verbal and graphic documentation. Such documentation provides the field staff with explicit information regarding sequencing of construction and Restricted Zones, as well as foundation, masonry and reinforcement requirements. Those same documents also provide opportunities for review by the prime contractor and designer of record. The bracing documentation also

Figure 4. Masonry walls under construction utilizing internal bracing. Courtesy of Koch Masonry, Dexter, Michigan and IMI – Internal Bracing Guide.

provides supplemental information for Special Inspectors to use as the basis for their inspections.

Written Content One key element of an Internal Bracing plan is the written portion, which provides the base assumptions and requirements represented graphically in drawings or, for simple projects, may provide the entire bracing plan. The content should include material properties, foundation and soils criteria, masonry construction sequencing and any assumptions relative to surrounding construction or site sequencing that were utilized in the bracing design.

Figure 3. Sample bracing plan graphics, notes and legend. Courtesy of Dailey Engineering, Onsted, MI and IMI – Internal Bracing Guide.

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Graphic Content The other portion of a bracing plan is the graphic content. For Internal Bracing this may simply be the foundation, and possibly framing plans, showing the walls and identifying the Restricted Zone. The plan(s) should include basic dimensions, notes regarding sequencing of the masonry construction and Restricted Zone implementation. Additional content could include ground and wall sign locations, control joints and walls used to buttress horizontal spans. Elevations, sections, and details can also be used to show important information, especially with regard to areas around openings and other points of discontinuity in the masonry. Proposed and accepted changes to the construction drawings also must be clearly represented in the bracing plan. Suggested bracing plan content is shown in Figure 2 and sample graphics, notes and a legend are shown in Figure 3, to illustrate some of the requisite items as utilized for this particular project.

Conclusion

the application of engineering principles for bracing using the wall’s inherent strength rather than external elements, i.e. internal bracing. The Internal Bracing Guide applies the content of the Standard and other documents, along with knowledge gained through experience, to provide users with one approach to designing internally braced masonry walls.▪ The online version of this article contains detailed references. Please visit www.STRUCTUREmag.org.

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Masonry walls must be braced while they are under construction to provide safety to construction workers and other persons that may occupy the space adjacent to those walls. The Standard provides the engineering basis for analyzing bracing methods for masonry walls under construction, and the Internal Bracing Guide offers more detailed instruction on designing internal bracing. Internal bracing utilizes the strength provided by the wall as it is being constructed, without relying on external components. Cooperation with, and collaboration between, bracing design engineers, mason contractors

and controlling contractors or construction managers are critical, and can yield highly efficient Internal Bracing schemes with significant benefit to projects in terms of safety, schedule and cost.

Figures 4 and 5 show two projects that utilize internal bracing. What is striking is the absence of external bracing on both projects.

Figure 5 shows a well-organized construction site that can lead to greatly improve site safety.

The Internal Bracing Guide is a document developed by IMI for engineers and other qualified persons designing masonry internal bracing systems. It outlines the process and illustrates

Structural DeSign design issues for structural engineers

T

his is a story about designing brick masonry curtainwalls. It is a story because the events did not all occur on the same project. They all happened, just on different projects.

For context and introduction, the author’s education is in solid mechanics followed by an early career in aerospace designing airplanes.

Leaving the aerospace industry to design buildings wasn’t easy. Knowledge about the design of aluminum structures provided no respect from fellow building design engineers. When a small research project involving brick masonry came into the office, everyone else was suddenly too busy. The job turned out to be a blessing. It was easy to become an expert in masonry; there was no competition. There were also projects to design aluminum curtainwalls that no one wanted. Thus, by chance, the author evolved into a perceived expert in brick masonry curtainwalls.

Moving forward 10 years, an email arrived from one of our project managers. “Are you available for a meeting with the Contractor, Owner, and Design Team to talk about the brick exterior wall this afternoon?”

“Sure, where?” The answer back is, “Don’t know yet – will let you know”. Two o’clock rolls around and we were off to the meeting.

The project is a large hospital, with over 500,000 square feet, in a seismically-active area that includes critical care, patient rooms, operating rooms and office space. The building is six stories with some five- and four-story sections and many corners. Our structural engineering firm had been working on the design with a noted architect for over six months. The gravity structural system is steel and the lateral system is concrete shear walls. The hospital is in a moderate-sized city that will service a large geographical area. The general contractor was on board, a large nationally known construction company, and the maximum project budget had been set. The architectural program was complete. A lot of effort had been expended on the design of the patient rooms. They were optimized for layout, including considerations of available cabinetry and other equipment, and were approved by the hospital management and staff. The dimensions were set and the owner had chosen a brick facade.

Twelve or more people were at the meeting, plus a video conferencing set-up to connect with the design architect in another city. A quick look at the drawings revealed the wall was a 4-inch brick veneer, with a 2½-inch insulated cavity, ½-inch exterior board and a 4-inch metal stud. Total thickness was 11 inches plus ½-inch interior wallboard for a total of 11½ inches. The brick dimension was 4-inch nominal, which

Brick Curtainwall for Essential Buildings

By John G. Tawresey S.E., F.TMS, F. SEI

John G. Tawresey S.E., F.TMS, F. SEI, is the retired CFO of KPFF Consulting Engineers in Seattle, WA. He received The Masonry Society’s 2012 Paul Haller Structural Design Award, serves on TMS 402/602 and ASCE 7 main committees, as well as on the ASCE/SEI National Technical Program Committee, and chairs the Professional Practices Committee of SEAW. John can be reached at JohnTaw@aol.com.

18 May 2014

meant the specified dimension is 4 inches minus the thickness of the mortar joint used to lay the brick, or 35/8 inches. The specified thickness of the wall was actually 113/8-inch. The floor-tofloor height varied between 13 feet 43/8 inches and 17 feet 43/8 inches, or 60 courses and 78 courses with an extra 3/8-inch for differential vertical movement between the floors. The architect obviously did this before [standard modular coursing, 3 courses per 8 inches].

A quick calculation using 20 psf [85+ miles per hour stagnation pressure] and 400S162-54 studs at 16 inches on center resulted in a deflection of 0.6 inches for the 13½ -foot story height and 1.7 inches for the 17½-foot story height.

This is a deflection of approximately L/270 and L/120 respectively.

The contractor and architects seemed somewhat disconnected from the meeting. Only later did we learn the reason; this was the same wall system used on the previous job. One problem with being knowledgeable about masonry, you often are required to deliver bad news and often get shot as the messenger.

Everyone was looking at the expert when I declared: “The 4-inch stud thickness is not adequate to support the veneer. And, a brick veneer on steel studs cannot meet the seismic drift requirements at the corners for an essential building.”

The TV blinked and then went blank [it really did happen]. The lesson learned is to be less disruptive. It would have been much better to compliment the designers on their attention to modulation, ask what kind of brick [color] they intended to use and offer to look into the design. The bad news could then be delivered with a solution, and possible extra service fee at a later meeting.

Instead, the contractor took control with one of those harsh and elevated voices. “The dimensions of the wall will not change.” The meeting ended with our project manager promising to look into it.

There are standard criteria for the deflection of the veneer-backing wall. Unfortunately, the criterion don’t agree with one another. Numbers can vary between L/2000 to L/175. The International Building Code (IBC) does not provide a number.

The L/2000 number will prevent any cracking of the brick veneer and the L/175 value is typical for the glass aluminum curtainwall industry. The Western States Clay Products Association recommends a value of L/360. The Brick Institute of America recommends a value of L/600.

Service wind loading was used for calculating the deflection limit. There is some room for interpretation of the service wind load definition. Most will use unfactored wind loading from ASCE 7 (Components and Cladding). But, the 85+ miles per hour wind has a return period of 50 years.

Could a lower value be used?

changing to another curtainwall material.

But, the owner was set on brick. Could we use thin brick set in 7½-inch precast panels and forget about the cavity? This was rejected because of the weight impact on the seismic design and the appearance, which usually does not look natural, not to mention the loss of the 2 inches of insulation. We could also add a horizontal girt system below the floor at the ceiling level to reduce the span. This last option, while adding significant cost, was the selected solution and solves the deflection issue (Figure 1).

But what about the performance of the brick veneer at the building corners? For the walls that are linear, the horizontal joint between floors, filled with caulk, could accommodate the seismic movement. But the joint doesn’t work at a corner and there were a lot of corners. The IBC “accommodation” of the seismic displacement Dp of 1.5 inches. What does accommodation mean for a brick veneer? Other sections of the IBC imply that the performance for a glass curtainwall is that the glass does not fall out of the frame. Could we imply from this that

Figure 1. Girt system.

STRUCTURE magazine

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Even at 50 miles per hour [stagnation pressure of 6.4 psf ], the analysis predicts the brick veneer will crack [typically at the mortar joint]. But after cracking, the span is divided in half, which reduces the stress by a factor of 4. The consequence of a larger deflection is a larger crack opening [0.04-inch at L/360] and possibly more water infiltration as a result. The brick would remain attached to the backing studs because of the ties. But the wall will leak more.

With a high quality air and water barrier behind the brick veneer [the project was to have one], the criteria of L/270 and ASCE 7 unfactored loads worked for the 13½-foot story heights. This could be the solution.

The principal-in-charge jumped in. To stay within the standard of care usually exercised by structural engineers in the area at the time, the L/360 limit and ASCE 7 unfactored wind loading is common practice. Attorneys assessing the structural engineer’s performance relative to the standard of care often correlate more water to more deflection and if there is a water problem, then there is a structural problem and we would be sunk.

What were we going to do? The meeting was scheduled in two days and everyone was extremely unhappy with us for creating this problem. Not our fault, but perceptions are reality. Internal meetings considered many suggestions, including

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Figure 2. Soft joint corner.

Figure 3. Isolated veneer backing.

the criterion for a brick veneer is that no brick falls out of the wall and cracking will be OK? All agreed that this criterion would be acceptable, including the principal-incharge who then left the room.

How to meet the criteria was the hard question!

With the 1.5-inch displacement and ties close to the corner, all agreed that the ties would pull out of the masonry or disengage from the stud by stripping the screw or by a tension failure. Sections of the wall would likely disengage from the backing.

Was the requirement for #9 wire joint reinforcement to engage the veneer tie a solution? No! Recent research demonstrated that adding the #9 wire joint reinforcement in the veneer to engage the tie did not help, and may reduce the capacity of the tie. (The requirement is no longer in the 2013 edition of the IBC.) It was clear that the conventional detailing of brick veneer at the corner does not satisfy the criteria.

A suggestion was made to provide a control joint at the corner. This is a common solution.

Architects hate the wide joints required, but sometimes accept them. The width of the joint would need to be 1½ inches or wider to allow for construction tolerances. Additionally, the joint would need to be close to the corner to minimize the stiffness of the return brick. The “eliminate the corner” option worked and sketches were prepared (Figure 2).

Another engineer suggested isolating the backup stud wall system. This would require a detailed design of the stud wall. Bracing would be required and the stud-head-track would be designed not to attach to the floor above at the corner. This would also reduce damages to the interior finishes and the brick could be detailed as the conventional veneer (Figure 3).

The project manager piped in: “There is no fee for this in our scope of work.” A fee proposal would be required with this option, or it could be a bidder-designed item and we could let the architect put it into the specifications.

Oops, the principal-in-charge returned. “The bidder-designed option is not an option. I have been there before. The metal stud low bid sub-contractor will miss the requirement and have no money to do it right. This is the stuff claims are made of.”

The author suggested reinforcing the veneer as a possible solution. This concept would replace the ties with floor and girt connectors. The reinforced structural masonry would span to the connectors. Connectors could be placed a distance from the corners, allowing the deflection to occur by warping of the wall [like a curtainwall]. The savings from the elimination of the ties [stainless steel was contemplated] equaled or exceeded the added cost of grout and reinforcement. But, past experience with owners, contractors and architects was mixed. The concept of warping brick corners was difficult to explain. Moreover, some of our own SE’s doubted it would work.

Brick is a brittle material.

“Is reinforced concrete a brittle material?

Reinforced brick appears to demonstrate more flexibility in the curtainwall test conducted under AAMA 501.4 than reinforced concrete.”

Who would do the design? It was not in our scope.

Despite the doubt, a reinforced veneer is added as a solution along with a fee proposal (Figure 4 ).

Sketches and presentation materials were prepared in a flat-out effort. With three proposals in hand, “elimination of the corner”, “isolated stud wall corner”, and “reinforced veneer”, we headed for the meeting, now at the owner’s headquarters.

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Figure 4. Reinforced veneer.

The air was thick. The perception was that this entire mess belonged to us. The General Contractor invited the CEO for the owner, and the design architect flew in from the faraway city. A mason contractor was invited to participate. The meeting began …….

The story doesn’t end here, just this article.

Structural engineering is a great profession.

Each situation is different and we get to solve many problems, most of them created by our clients. But, each day is different and in the end we get to participate in the creation of great projects.▪ Post Script: Don’t put a deflection limit in the IBC. One criterion does not work for all projects and clients. Moreover, adding a prescription to the code eliminates the opportunity to be creative. I prefer to be a consultant that uses judgment and experience to customize designs and recommendations for my clients. And, it offers the opportunity for a design fee that adds value to the project.

For more information on Reinforced Brick Veneer, see the Design Guide for Structural Brick Veneer from Western States Clay products Association at www.brickwscpa.org/publications.php.

As a structural engineer, my primary concerns are always structural reliability, ease of install for the contractor, and final quality provided to the owner. Simpson Strong-Tie is the only manufacturer that inspires 100% confidence in all three areas and represents the best of the best in the industry: quality products and top of the line service to back it up.” Jake Morin – Structural Engineer, Tempe, AZ To learn how our commitment to quality, innovation and support adds value to you and your business, call (800) 999-5099 or visit strongtie.com/genuine.

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The Sky is Falling!

No, It’s Marble!

Stone Repair at the Fairmount Cemetery Mausoleum

By Stephen H. Getz, BSCE

F

ailing anchors in marble ceiling panels limit access for ceremonies and visiting patrons for interred loved ones in the mausoleum (Figure 1). Constructed in the 1920s, the Fairmont Memorial Mausoleum is located on the 150 acre grounds of the Fairmount Cemetery in Newark, New Jersey. The 250 foot long by 92 foot wide “H” configured building has an exterior built of granite upon a cast-in-place concrete frame and concrete floor infrastructure. There are four functional levels to the building, including the basement. The interior walls and ceiling are veneered with 1- and 2-inch thick marble stone panels. The interior mausoleum environment was not conditioned for climate, and over nine decades of changing weather has challenged both the stone durability and anchorage connections.

Interior Stone Veneer Construction

Figure 1. Exterior of the Fairmount Mausoleum.

one inch thick marble. The marble pieces span the hallway and are simply supported at the end. A center wire tie was observed in an inspection of an exposed beam. The length of the beams varies from 7 feet to approximately 10 feet in some areas. At most locations, the marble box is a nominal 18 inches wide by 18 inches deep.

The stone ceiling panels (Figure 2) are configured such that four (4) panels are butted to form a square. Each of the four panels has two edges common to another panel. They are suspended near center by copper wire ties attached to the stone edges by field-bending the wire to achieve about a 1-inch deep embedment in the stone. The wire’s opposing end is tied to the reinforcement bar of the floor above within a pocket created by chiseling the concrete cover to expose the ceiling rebar. The integrity and effectiveness of the existing ties are questionable, although such a system was not unusual at the time (Figure 3).

Figure 4 illustrates the typical anchorage of the 8-gauge copper wire ties on a removed panel segment. Typically, the ties occurred at 12 to 16 inches from the unsupported free end, or mid-hallway location, of the panel. The outer perimeter of the 250 – 300 pound stone panels is supported by the vertical wall panels lining the hallway. The chase between ceiling panels and concrete differed by floor and the distance between the stone panel and concrete varied from 14 to 41 inches.

The hallways throughout the building have marble encased concrete beams (Figure 4 ) occurring at approximately 8- to 10-foot intervals.

Where concrete beams did not exist, a faux marble beam was provided for aesthetic continuity. The beams are covered on three sides with

The untimely collapse of a ceiling panel alerted the owners to the potential dangers of future collapse, and that repair was essential and urgent. The task to remove and reset the hundreds of heavy ceiling panels and three piece marble clad beams was not financially feasible.

The marble veneer providing a wall covering was intact and functionally sound. Accordingly, the project team investigated a cost effective supplemental anchoring solution.

The challenges in developing the anchoring repair included: • Developing a post-installation anchor to bridge chase distances of 14½ to 43 inches; • The anchor must be capable of supporting a working load of 350 pounds tension and not induce tension loads on the existing marble panels; • The anchor assembly must interact with the stone panels so that a face mount anchor will support the stone panel without stone fracture; • Providing anchorage spacing and location dimensions that optimize anchor performance and does not over-stress marble;

Figure 2. Interior of marble clad ceiling, beams, and walls.

Figure 3. Corroded tie connection to steel.

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Figure 4. Typical 18- x 18-inch concrete beam enclosure in hallway.

Figure 5. Details for ceiling anchors.

• Developing an anchoring scenario for stairwell ceiling panels installed at an angle to match the pitch created by the stairs; • Anchor finish must be aesthetically matched to the existing wall artifacts, sconces, gates and miscellaneous metal hardware; • Developing a beam enclosure anchorage system to capture and support the marble box beam enclosures; • Providing necessary installation means and methods criterion to assure marble and anchor combination effectively perform efficiently.

Anchors Developed Marble Ceiling Panels For the basic ceiling panel anchor, CTP developed a ½-inch diameter brass expander element, torque activated for the concrete connection.

Torque provides an important means of inspection and performance

assurance. The anchor’s embedment depth in the concrete was tested at a minimum of 1½ inches that averaged over 1200 pounds capacity and induced a preload of 1060 pounds. These results provided safety factors greater than the industry standard of 4:1. The 4-inch floor in which the anchor would be fastened allowed the air space to vary 2 inches shorter, providing a standard shaft length for the variable condition. The head of the anchor is a 1½-inch diameter stainless steel round bearing plate capable of supporting the stone. The two elements are connected by a suitably long stainless steel shaft assembly (Figure 5).

The marble ceiling panels were installed with corners butted at the center of the hallway. The 1½-inch diameter panel head would challenge the installation at this location due to the improbable ability to support each panel equivalently. As a result, a larger support area was required and a bearing plate was incorporated to support the panels in concert with the 1½-inch round panel head (Figure 6 , page 24).

Each bearing plate is manufactured of Type 304 stainless steel with

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7974 W. Orchard Drive Michigan City, Indiana 46360-9390 • USA Phone: (219) 878-1427 Contact: Steve Getz, BSCE www.ctpanchors.com Engineered Anchoring Solutions Provider

Figure 6. Typical ceiling support assembly.

Figure 8. Box beam enclosure assembly for an 18- x 18-inch beam.

Figure 7. Beam enclosure anchor.

a brushed finish. The bearing plate design was predicated upon the panels being supported at the outboard edge. As a result of this support configuration, the bearing plate will carry one half the weight of the panel. The ceiling panels are installed as pairs, meeting at center line of the aisle way ceiling. The bearing pad used was to cushion the contact area of the steel member against the stone.

Anchor assemblage components are manufactured of corrosion resistant materials. This style of anchorage was used throughout the project. The length of the anchors varied according to the cavity between the stone and the concrete slab, by floor. Three different anchor lengths were finalized after a field survey. Except for an extended drilling depth, all the assemblies followed the same installation instructions. This was an important feature in order to avoid customizing individual anchoring assemblies.

and right bearing brackets require bearing pads to insulate the stone from contact unit stresses.

To prevent the box beam side-wall stone panels from collapsing inward, they are anchored to the left and right strap assemblies as a final connection of the hardware to the stone. A masonry fastener incorporating Type 360 brass expander elements with 18-8 stainless steel hardware was applied. These fasteners are torque activated to maintain intimate contact of the marble side wall panels with the support hardware. The anchor length allows a portion of the expander to project from the rear side of the marble. As the anchor is torque activated, it creates a “rivet” connection effect between the stone and steel strap.

The bracket assemblies are manufactured of Type 304 stainless steel.

Summary

Stairwell Marble Ceiling Anchors The assembly used in the stairwells for supporting the ceiling panels incorporates the same hardware as the ceiling panel support anchors.

The panels in this area were installed to complement the stair rise and run angle. The panels are confined, and thrust loads due to the angularity were not an issue because of the panel confinement. A ceiling shim, manufactured of Type 303 stainless steel, was used to “normalize” the loading application from the plate to the Stone-Grip head.

Beam Enclosure Support Assembly The beam enclosure support assembly incorporated the same style of anchorage to concrete used for other conditions. There are three (3) anchors per enclosure assembly and two encasements per beam (Figure 7 ). The anchor lengths vary with the depth of the beam.

The box-style beams’ varying height and width required an adjustable support hardware configuration. Basically, in order to transfer gravity loads, intimate contact with the marble is essential for the support characteristics of the load carrying system to be effective. Each box beam assembly consists of two upper-side mounted brackets. They carry the weight of the box beam and can be adjusted both horizontally and vertically. Additionally, they provide support to the ceiling panel adjacent to the beam. Each bracket can carry 240 pounds.

The top-side brackets are connected to a left- and right-side bearing bracket. This strap system envelops the beam and overlaps at the center of the beam bottom. Here too, the strap is capable of both vertical and horizontal adjustment to assure stone contact is made.

Once the side brackets are positioned, they are bolted to the top-side brackets via a 3/8-inch stainless steel stud, nut and washer. The stud is factory welded to the side strap bracket. The intent is to support the beam in the event of a primary failure of the original tie/support system. Similar to the bearing plate detail, a “bearing pad” is used in the gravity bearing support areas. The top-side brackets and the left STRUCTURE magazine

The finalized ceiling support assembly was used at 1,050 locations throughout the building for 1- and 2-inch thick marble. The marble beam enclosure and support assemblies were used at 370 locations throughout the building.

The entrance level (first floor) and second floor required the center anchor to span a maximum of 31½ inches, and the two top supports 14 inches; the third level was 43½ inches at the center support and 25 inches at the top side supports.

A critical element to the anchor installation was the method used to drill through the stone. Dry-drill carbide tip non-impact stone drilling bits were used for the task, as well as concrete drill bits 52 inches long having SDS drives to install the concrete anchors.

The quality and resourcefulness of the project team contributed to a successful execution of the restoration project, and provided a result that fulfilled functional and aesthetic concerns while completing the project weeks ahead of schedule.▪

24

Stephen H. Getz, BSCE, is the owner and President of Construction Tie Products (CTP) in Michigan City, Indiana. CTP specializes in the development of masonry and stone cladding restoration systems.

Steven continues participation in various trade related organizations that strive to develop relevant Standards and Codes aimed at the construction and preservation of quality masonry structures. He can be contacted at steve@ctpanchors.com.

A similar article was previously published in the The Applicator, 1st Qtr, 2014, produced by the Sealant, Waterproofing & Restoration Institute. Content reprinted with permission.

May 2014

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Guastavino Masonry shells

By John Ochsendorf, Ph.D.

I

n the late 19th and early 20th centuries, the Guastavino Company designed and built some of the most exceptional masonry structures in history. By adapting a traditional Mediterranean vaulting method to the demands of American construction, Rafael Guastavino Sr. (1842-1908) and Jr. (1872-1950) had a major impact across the United States. Between 1889 and 1962, the firm installed structural masonry vaults in more than 1,000 major buildings across the country, including long-span domes for numerous government facilities, museums, and religious buildings. By 1910, they were able to construct vaulting on an industrial scale, with more than 100 projects under construction simultaneously. A company advertisement from 1915 illustrates some of these domes (Figure 1).

This article provides an overview of Guastavino vaulting and identifies noteworthy structural achievements by Rafael Guastavino, Jr. as well as calculation approaches for masonry vaults. Finally, the article describes the potential for Guastavino-style vaults to be built in the future.

History and Construction The Guastavino method of masonry construction uses thin ceramic tiles, roughly 6 x 12 x 1 inches, which are laid flat in multiple layers.

This method was considered to be revolutionary in the 14th century, when it was first described as being a lightweight and inexpensive method of construction compared to traditional stone vaulting (Figure 2). The tile vault appears to have been developed by Moorish builders near Valencia, Spain, though it quickly spread to become common throughout the Mediterranean region. The method is known as the bóveda tabicada in Spanish and is sometimes called the timbrel vault (so-named by Guastavino Sr.) or the Catalan vault (so-named by 20th century Catalan architects).

When compared to traditional stone vaulting, tile vaulting uses much less material and can be built much more quickly. Because the thin bricks are laid flat, with their narrow edges in contact, the total thickness of the vault is less than conventional masonry, and therefore the self-weight and corresponding horizontal thrust values are reduced. In the traditional tile vault, the tiles are joined with plaster STRUCTURE magazine

Figure 1. Advertisement for the R. Guastavino Company (ca. 1915) (Source: Avery Library, Columbia University).

of Paris, which sets quickly enough that the interior of the vault does not require any support from below during construction. By contrast, a traditional stone arch must be supported on wooden centering, or formwork, and will only support its own weight once the keystone is in place. By building out from a wall in successive arcs, tile vaulting can be constructed with minimal to no formwork.

In addition, the inherent fire resistance of the tile vault was a major selling point for the Guastavino Company in the late 19th century.

Though other builders had brought the tile vaulting method from Spain to the Americas as early as the 16th Century, Rafael Guastavino

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Figure 2. Comparison of the traditional stone vault (a) and the Guastavino tile vault (b) (Source: Moya, 1947).

Sr. and Jr. introduced numerous innovations to the traditional tile vault, which allowed them to secure dozens of U.S. patents to protect their product.

Guastavino Sr. was educated as both an architect and an engineer at the school of “masters of works” in Barcelona in the 1860s, by the same professors who would later teach the Catalan master Antoni Gaudi (1852-1926). In Barcelona, Guastavino Sr. constructed a series of major industrial factories as well as numerous houses, all using the traditional tile vault as the load-bearing structure for floors and staircases. His last major work before immigrating to the United States in 1881 was the La Massa Theater in Vilassar de Dalt, with a 56-foot span built of unreinforced masonry only 4 inches thick.

This astonishing thinness is possible because of the double-curvature of the masonry shell, which allows for compressive load paths to be transferred to the supports in multiple directions.

Figure 4. Crossing dome of the Cathedral of St. John the Divine by Rafael Guastavino, Jr., New York City, 1909 (Source: Avery Library).

With minimal English and few professional contacts in the United States, Guastavino Sr. initially struggled to earn a living as a newlyarrived immigrant. Eventually he got his break when he was contracted by the leading firm of McKim Mead and White to build structural tile vaulting throughout the Boston Public Library in 1889. This launched his American career and led to dozens of other contracts for structural tile installations in the 1890s. His son, Rafael Jr., had no formal education in architecture or engineering, but after apprenticing under his father, went on to build some of the most daring masonry structures in history.

Structural Achievements

by Rafael Guastavino Jr.

Figure 3. Grace Universalist Church by Rafael Guastavino Jr., Lowell, Massachusetts, 1895 (Source: Avery Library).

STRUCTURE magazine

Guastavino Jr. supervised the construction of an impressive church dome in 1895 when he was only 23 years old (Figure 3). The 70-foot span tapers in thickness from 6 inches at the support to only 4 inches at the crown of the dome, and the span-to-thickness ratio of roughly 200 is twice as thin as an eggshell by proportion. This dome was built in less than two months and was self-supporting throughout construction, with minimal formwork to guide the geometry. Because tensile hoop forces would appear in the lower region of the spherical shell – below about 52 degrees as predicted by membrane theory – Guastavino provided a tensile band of steel to resist the outward thrust at the intersection of the buttressing barrel vaults and the dome. As

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the ultimate load capacity of such a structure is extremely difficult even today, the Guastavino Company conducted many successful load tests, and the survival of the stair for the last century is proof of its adequate load capacity.

Mechanics of Masonry

Figure 5. Tile vaulted staircase of Baker Hall, Carnegie Mellon University, Pittsburgh, 1914. Courtesy of Michael Freeman.

with his father’s dome at La Massa, structural shells of this scale and proportion would not be constructed in thin shell concrete until decades later. In some ways, the Guastavino shells are superior to the later reinforced concrete shells because of the absence of formwork as well as the minimal reinforcing steel. Hundreds of Guastavino domes have functioned as safe structures for more than a century, and none have ever failed in service.

The largest dome ever built by the company is the 135-foot span for the Cathedral of St. John the Divine in New York City (Figure 4, page 27 ). Shortly after his father’s death, Guastavino Jr. proposed the dome as a temporary solution over the crossing of the cathedral.

By following a spherical geometry, the dome could be built using only cables to guide the placement of tiles, while the masons were supported on the concentric rings of tile as the project cantilevered out into space. This great feat of construction was completed in only 15 weeks during the summer of 1909, and was heralded as an achievement to rival the great masonry domes of antiquity. As in other Guastavino domes, the total thickness at the crown is just over 4 inches, and steel tensile reinforcement at the base helps to restrain the outward thrust of the dome. More than a century old, the dome still stands today as a testament to Guastavino Jr’s skill in both structural design and construction.

Though smaller in scale than the large domes, Guastavino spiral vaulted staircases represent an additional category of structural achievement. The main staircase of Baker Hall at Carnegie Mellon University is a masterpiece of Guastavino construction, with a 4-inch thick shell of masonry spiraling in three dimensions (Figure 5). The load-bearing masonry structure is made only of brittle ceramic tiles and does not contain reinforcing steel. The stair is constrained by a cylindrical brick structure, which resists the outward thrust of the vaulted staircase. Though calculating STRUCTURE magazine

Rafael Guastavino Jr. calculated the forces in his vaulted structures using compressive equilibrium solutions defined by graphic statics, and he often shaped the structures to respond to the flow of forces, placing masonry where the resulting thrust lines acted (Figure 6 ).

The goal of the calculation is to demonstrate safe equilibrium solutions under all possible load cases, and to ensure that the resulting thrust lines do not exit the masonry. This follows in the tradition of limit analysis of masonry as developed by Jacques Heyman since the 1960s. The stresses in traditional masonry structures are quite low, and the safety of such structures is typically governed by stability and not by strength.

By contrast, it is very difficult to demonstrate the safety of thin masonry shells using finite element methods, which seek to minimize the strain energy by invoking assumptions about the material behavior. Such elastic solutions predict substantial tensile stresses in traditional masonry and are highly sensitive to small movements of the supports. The calculation methods used by the Guastavino Company are similar to those used by the leading concrete engineer Robert Maillart and the great shell builder Felix Candela: they are based primarily on static equilibrium and not on the vain search for exact stress distributions in a hyperstatic structure. While assessing the safety of Guastavino structures remains a challenge today, new methods of equilibrium calculations can help today’s engineers to discover load paths that these masonry shells have effortlessly found for more than a century.

Several recent projects have demonstrated the potential for structural masonry shells to be built today. For the Pines Calyx project in England, two masonry domes span approximately 40 feet as the primary structural system (Figure 7 ). Similar to the unreinforced Guastavino masonry shells, the domes are constructed of three layers of thin tile, and the outward thrust is resisted by a tension tie at the

Figure 6. Graphic statics used by Guastavino Jr. to calculate the compressive forces in the dome of St. Francis de Sales Church in Philadelphia, 1909 (Source: Avery Library).

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base. The domes were self-supporting during construction, and a central oculus admits natural light and ventilation.

Equilibrium calculations based on the membrane theory and graphic statics were used to demonstrate the safety of the structure during construction and under asymmetrical live loading. Due to the use of local materials and the minimization of structural steel, the embodied energy in the structure is dramatically lower than conventional steel or reinforced concrete structures.

Conclusions 9/3/09 10:09 AM Page 1 The thin structural shells of the Guastavino TAY24253 Company BraceYrslfStrctrMag.qxd Figure 7. Structural tile dome, Pines Calyx, St. Margaret’s Bay, England (2005). are some of the most impressive masonry structures in the world. In particular, the large domes and remarkable staircases

by Rafael Guastavino Jr. are worthy of Y O U B U I L D I T. additional study by both engineers and hisW E ’ L L P R O T E C T I T. torians. More than 600 existing projects in more than 40 U.S. states contain examples of Guastavino masonry vaulting, though new projects are being rediscovered each year. The engineering calculation of thin Stand firm. Don’t settle for less than the seismic protection masonry shells presents an open challenge, of Taylor Fluid Viscous Dampers. As a world leader in and the engineer must find three-dimenthe science of shock isolation, we are the team you sional compressive solutions that lie within want between your structure and the undeniable forces the thickness of the masonry. Attempts to of nature. Others agree. Taylor Fluid Viscous Dampers prove the safety of existing structures can are currently providing earthquake, wind, and motion also lead to the discovery of new structural protection on more than 240 buildings and bridges. forms that have not yet been invented. The minimization of reinforcing steel and From the historic Los Angeles City Hall to Mexico’s the use of local materials can inspire engiTorre Mayor and the new Shin-Yokohama High-speed neers to design and build new masonry Train Station in Japan, owners, architects, engineers, vaults in the future, with the and contractors trust the proven hope of matching the success technology of Taylor Devices’ and longevity of Guastavino Fluid Viscous Dampers. tile vaulting.▪

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For More Information A public exhibition on Guastavino vaulting, including original design drawings and a full-scale replica vault, is on view at the Museum of the City of New York until September 7, 2014. For further reading on the subject, the online version contains an extensive list of suggested texts. Visit www.STRUCTUREmag.org.

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John Ochsendorf, Ph.D. (jao@mit.edu), is a structural engineer specializing in the mechanics and construction of historic masonry. He is the Class of 1942 Professor of Engineering and Architecture at the Massachusetts Institute of Technology and is author of the book, Guastavino Vaulting: The Art of Structural Tile.

Tensioning Masonry to New Heights

Armory Park Elderly Housing Project

By Kelly Robertson, P.E. and Paul Scott, P.E., S.E.

T

Figure 1. Elevation.

he tallest post-tensioned masonry building in the United States was completed in 2013 in Sentinel Plaza, an Independent Senior Housing Development, in Tucson, Arizona. The new building is six stories high with 139,000 square feet and 143 units (Figures 1 and 2).

Within the Sentinel Plaza Development was an existing building called Armory Park. Armory Park, a HUD 202 building, had been determined to be outdated and needed to be replaced. SHG (Senior Housing Group), using Arizona Low Income Tax credits, took on the task of building the replacement building, which is also called the Armory Park building.

The Sentinel Plaza Development requires sustainable architecture design for the buildings in the development. Armory Park was designed to meet LEED (Leadership in Energy and Environmental Design) Gold standards. Roof mounted solar modules offset 75% of the common area’s electrical loads. Landscaping uses drip irrigation, low water use native plants and passive water harvesting. High efficiency mechanical units, low water use plumbing features and high performance windows were used.

As a part of achieving the LEED Gold, the exterior walls were required to contribute to the energy savings by having an average R value of 16. Four exterior wall systems were evaluated/considered: Masonry Walls Pros • Masonry is a common exterior wall system in Tucson, AZ. • The exterior masonry walls can be the Post-Tensioned Masonry Wall System and achieve an R = 19 for 8-inch thick CMU (concrete masonry unit) walls.

• Grout and rebar can be used in masonry for detailing as required by structural calculations.

• Masonry is a very durable exterior wall surface.

Cons • Masonry is not viable as the exterior wall unless a significant R value can be achieved with the masonry wall or with furred out walls with insulation.

Concrete Walls Pros • Concrete is a common exterior wall system in Tucson, AZ. • Concrete is a very durable exterior wall surface.

Cons • Concrete walls cannot achieve an R of 19 unless the walls are sandwich panels with Styrofoam/ high density polystyrene in the middle of the concrete wall, or if walls are furred out and insulation is used in the furred out walls.

Steel Studs Pros • Steel studs are a common method to build exterior walls in Tucson, AZ. • Insulation can be placed between the steel studs to achieve the required wall R value.

Cons • The steel studs allow for thermal transfer of heat/cold from the exterior to the interior through the steel webs of the steel studs.

• The exterior material (stucco over gypsum board) on the steel stud walls is not as durable as masonry or concrete exterior walls.

Figure 2. Plan view.

STRUCTURE magazine

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Figure 3.Under construction.

Figure 6. Detail of standard CMU units.

Figure 4. Plank floor with CMU bearing walls.

Figure 5. Building under construction.

Insulated Concrete Forms (ICF) Walls Pros • ICF walls can provide the wall R value required.

Cons • ICF walls are not as common as masonry, concrete, or steel stud exterior walls in Tucson, AZ. • The exterior material (stucco over the insulating foam form) is not as durable as masonry or concrete walls.

The original LIHTC (Low Income Housing Tax Credit) application included ICF as the load bearing & insulated exterior wall system. The general contractor (W.E. O’Neil) suggested post-tensioned masonry as an alternate system for several reasons: durability, ease of construction, and similar insulating characteristics. Additionally, the CMU STRUCTURE magazine

met LEED requirements for local sourcing. After an evaluation of the relative cost, schedule impacts, and LEED requirements, a posttensioned masonry wall system was chosen to be used as the exterior wall (Figures 3, 4 and 5).

Superlite Block (an Oldcastle Division in Phoenix, AZ) developed the “Post-Tensioned Masonry Wall System” (Integra) in 1984. The post-tensioned system was developed in order to provide a structural masonry wall with significant R value. Superlite was issued an ICBO report in 1991, which is now ICC Legacy Report ER-4845. (This ICC approval preceded the development of the Prestressed Masonry chapter in the Building Code Requirements for Masonry Structures (ACI 530/TMS 402/ASCE5) and is still being used. The ACI 530 is available for prestressed masonry design and is used by most designers.)

The post-tensioned system can be designed using either Allowable Stress Design (ASD) or Ultimate Strength Design (USD) as outlined in the ICC Legacy Report. ASD was chosen for this project, as ASD has been used in the majority of Integra projects done to date. The design procedure used follows the simple design principles: P/A and M/S. The allowable stresses in the Legacy Report are based on full scale load tests done in 1991 at the NCMA (National Concrete Masonry Association) Lab in Herndon, VA. The allowable stresses are as follows: Axial Compression – 360 psi Axial Tension – Not Allowed Bending Compression – 540 psi Bending Tension – 22 psiI Shear – 59 psi The system uses 7/16-inch diameter smooth steel rods as the posttensioned rods (PT rods) with Fy min = 60 ksi. The post-tensioned rods are tensioned to 7,400 pounds and the usable tension in each rod is 5,000 pounds taking into account the losses. See Figure 6 for the CMU units used.

The post-tensioned system was designed initially to be used as an exterior residential wall. However, it has also been used in many commercial projects like the Armory Park project. The main differences, in residential versus commercial design, are the magnitude of the loads, the height of the walls and the size of wall openings. There have been some residential projects where all of the masonry walls have been post-tensioned, meaning no grouted cells were required.

Those structures can use the total R = 19 for an 8-inch thick wall.

Most residential and commercial post-tensioned projects require some locations in the wall with solid grouting or solid grouting with rebar, therefore an average R value can be computed. For example, wherever there is a need for a bolted connection of a ledger to a wall, the bolts are placed in a solid grouted bond beam with two

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N Figure 7. Key plan of wall elevations.

Figure 9. West elevation “T”.

Figure 8. Partial north elevation “I”.

pieces of rebar. Wherever there is an opening large enough that the post-tensioned system won’t work, a reinforced solid grouted jamb is designed.

Structural Factors • The seismic response modification coefficient R for ordinary reinforced masonry walls is 3.5 versus 1.5 for the R of ordinary prestressed masonry walls (Reference Table 12.2-1 ASCE 7-05).

Discussion – The seismic lateral loads were larger than the wind lateral loads, so using an R of 1.5 versus an R of 3.5 increased the lateral loads on the building. The increase in lateral loads turned out not to be a significant design concern because the amount of masonry walls available was adequate for the R = 1.5 and the interior party walls were reinforced masonry, not post-tensioned.

• There were concerns that the masonry contractor would have difficulty determining where the post-tensioned CMU occurred versus the conventionally reinforced CMU. Discussion – The post-tensioning structural engineer decided to provide elevations of all the exterior walls. The elevations showed STRUCTURE magazine

every concrete masonry unit and, through the use of different shading and hatching, the post-tensioned CMU could be distinguished from the conventionally reinforced CMU. Every post-tension rod was shown, every piece of re-bar was shown and grout locations were shown (Figures 7, 8 and 9).

• Post-tensioning didn’t work at all of the exterior walls.

Discussion – The post-tensioning system was used for the entire six stories at the non-bearing walls. At the bearing walls, the compression due to the vertical loads and the post-tension rods compressing the walls was significant. Therefore, only the top two floors are post-tensioned at these locations.

• Detail coordination between building engineer (SEOR) & the Post-tensioning Designer.

Discussion – Because post-tensioning is often treated as a deferred submittal in the design process, the Structural Engineer of Record has typically already completed the structural detailing prior to the post-tensioning being designed.

The structural details may show conventional masonry or they may dash in the post-tensioning masonry walls to be designed by others. In the case of Armory Park, the completed details by the SEOR showed the post-tensioning masonry dashed in, so the design team was able to base the connection details off of the structural details and include the information required for the post-tensioning construction. This coordination allowed the details to appear consistent between the structural drawings and post-tensioning drawings, and each consultant was able to review the details and verify acceptability prior to being finalized (Figures 10, 11, 12, and 13).

Quest Energy Group provided the energy modeling services for the building. TestMarcx Commissioning Solutions provided commissioning for LEED for Homes Midrise credits EA Pre-requisite 1.2 (Energy & Atmosphere Optimize Energy Performance: Testing and Verification) and EQ 12.1 and 12.2 (Indoor Environmental Quality:

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Figure 11. Detail of precast concrete at post-tensioned wall with parapet: bearing.

Figure 10. Detail of precast concrete at post-tensioned wall: bearing.

Figure 12. Detail of concrete over steel deck at post-tensioned wall.

Figure 13. Detail of post-tensioned wall above conventional CMU wall.

Prerequisite And Enhanced Compartmentalization of Units). Pima County Development Services Green Building Program served as the LEED for Homes Provider and Green rater, and also provided Durability Management Verification (credit ID 2.3). The post-tensioned masonry system contributed to the following LEED midrise points: • ID 2.1, 2.2 and 2.3 (Quality Management for Durability) • ID 3.1 (Innovation and Design for exemplary performance in SS 5 Pest Control) • SS 5 (Nontoxic Pest Control) • EA 1.1 and 1.3 (Minimum and Optimize Energy performance) • MR 2.2 (local production, exterior wall) Throughout construction, all lines of communication ran through the architect, so that all consultants would remain coordinated. Because of the thorough coordination effort during the design process, field coordination issues were kept to a minimum. With this practice in place, the award-winning Armory Park project was successfully completed ahead of schedule.▪ STRUCTURE magazine

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Project Team Owner: Senior Housing Group, Tucson, AZ Structural Engineer of Record: Schneider & Associates Architect: Lizard Rock Designs, Tucson, AZ General Contractor: W.E. O’Neil, Phoenix, AZ Masonry Contractor: Hobbs Masonry, Phoenix, AZ Masonry Supplier: Superlite Block , Phoenix, AZ Post-tensioning Design Structural Engineer: Caruso Turley Scott Inc. Kelly Robertson, P.E., is a structural engineer at Caruso Turley Scott, Inc. in Tempe, AZ. She can be reached at krobertson@ctsaz.com.

Paul Scott, P.E., S.E., is a Partner at Caruso Turley Scott, Inc. He can be reached at pscott@ctsaz.com.

May 2014

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R

ecent decades have seen major changes in methods of structural design and analysis. The allowable stress approach was applied to all materials for decades until, many years ago, the principles of strength design for reinforced concrete were introduced; they are now the norm for the design of such elements in the modern world. In more recent history, strength design methodologies have been developed and adopted for other common materials such as steel, masonry, and even wood. Though many engineers have initially resisted the idea, the ‘new’ provisions and methods of strength design have become generally accepted.

Those familiar with both allowable stress design and strength design tend to agree that the latter provides a more reliable prediction of element behavior at its ultimate state, usually with a less conservative outcome. It stands to reason that members designed using the strength methodology should generally have a higher predicted capacity than those designed using the traditional stress methodology. However, there are subtle nuances in strength design that cannot be overlooked, which may come as a surprise.

Perhaps the largest benefit of the strength design methodology is the concept of ductility, which might also be termed controlled failure. The idea is that we do not design the members to fail; rather, we design them so that if they fail, they do so in a ‘safe’, ductile, predictable manner, hopefully allowing egress of occupants prior to collapse. Consider the following scenario: A slender masonry wall may be demonstrated to have the capacity to support the required loads when designed using the more traditional allowable stress methods. However, the wall might actually be over-reinforced such that crushing failure could occur prior to yielding of tensile steel, violating a basic tenet of the strength design method.

Section 3.3.3.5 of TMS 402-11/ACI 530-11/ ASCE 5-11, Building Code Requirements for Masonry Structures, outlines the maximum area of flexural tensile reinforcement for masonry elements proportioned using strength design. In short, the provision prescribes an ultimate strain scenario, which will ensure that tensile reinforcement yields prior to masonry crushing. Hence, a ductile, controlled flexural failure mechanism

Masonry flexural strain diagram at ultimate capacity.

is ensured. Though the code provision for this concept is presented in a different manner than its concrete counterpart, the idea is the same. In general terms, the amount of flexural reinforcement in a masonry member should be such that a minimum tensile strain of at least 1.5 times the yield strain is achieved prior to the masonry crushing in the compressive zone. This concept is presented in accompanying graphic.

Masonry is assumed to fail in compression at a prescribed stress of 0.80f 'm . Using this value, the Whitney stress block that is familiar from reinforced concrete design (a = 0.80c), and the linear relationship of the strain diagram results in the following equation for maximum area of steel: A s,max =

0.80

(

aids for the structural engineer’s toolbox

)

emu d b(0.80f 'm ) – P 1.5ey + emu fy

where emu is the maximum allowable usable strain (0.0025 for concrete masonry and 0.0035 for clay masonry), ey is the bar yield strength, and b, d, f 'm , and P represent the dimensions, specified masonry strength, and axial load, respectively.

For practical application, this provision comes into play commonly in slender elements such as the wall scenario mentioned previously, where the effective depth is relatively low, the axial load is somewhat high, and the specified masonry strength (e.g., f 'm = 1,500 psi) is relatively low. Reduced effective depth translates into lower tensile strains.

Likewise, axial loads reduce reinforcement tensile strains while increasing compressive stresses on the masonry. This leads to shallow (slender/thin) elements carrying axial load being the most likely masonry elements that might be classified as ‘overreinforced’ using strength design methodologies.

For this case, it would not be unusual for the #5 vertical bars commonly centered in 8-inch masonry walls to violate the TMS 402-11/ACI 530-11/ ASCE 5-11 strength design provisions, whereas the same configuration may be acceptable using the allowable stress design provisions.

Such a result does not necessarily mean that an acceptable ASD design should be characterized as ‘unsafe’. It is simply a reflection that ASD methods do not target a specific kind of failure as the ultimate state. The ASD method examines the working stresses on both the masonry and the reinforcement, and ensures that they are well below the corresponding limits. It does not necessarily address which component would fail first, but simply aims to preclude any failure of the constituent materials under service loads. By contrast, the strength design procedure targets a reliable, ductile mechanism as the primary mode of behavior, should actual loads surpass practical expectations. As such, it is deemed more reliable and less conservative than the ASD approach.▪

STRUCTURE magazine

EnginEEr’s notEbook

Flexural Masonry

35

Stress Design Works, Strength Design Fails?

By Jerod G. Johnson, Ph.D., S.E.

Jerod G. Johnson, Ph.D., S.E. (jjohnson@reaveley.com), is a principal with Reaveley Engineers + Associates in Salt Lake City, Utah.

A similar article was published in the Structural Engineers Associations-Utah (SEAU) Monthly Newsletter (March, 2007). Content reprinted with permission.

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STR_7-13

new trends, new techniques and current industry issues

InSIghtS

Structural Health Monitoring of America’s Infrastructure

By Duncan Paterson, P.E., Ph.D.

W

hen we think of bridge health evaluation, the traditional means and methods have been inspection by engineers in the field and ratings based on loading assumptions. Bridge inspectors are the original non-destructive evaluators, using observation and diligent records to establish how a bridge is performing during its life cycle. The term NonDestructive Evaluation (NDE) has a greater implication, though; we are doing more than a visual evaluation. NDE is becoming the term to differentiate between what we think of as customary inspection techniques, and using advanced electronics and data evaluation.

A subset of NDE is Structural Health monitoring (SHM), a term that indicates response monitoring, damage detection system(s), or other observation systems for structural response over time. SHM has steadily increased in the bridge community’s vernacular over the past few decades. Once, the thought of placing system response instruments on or near bridges was solely the domain of academia and research. SHM, however, has the capability to provide a direct link between loads and bridge behavior; it can surpass traditional assumptions for ratings and provide actual structural response to loads.

SHM has been evolving since its inception as a means to establish the effects of load on bridges and structures. The main workhorses of SHM remain strain gages, tilt-meters, accelerometers, and displacement gages. For those not familiar with these devices: strain gages evaluate a nominal displacement of a surface over a known gage length; tilt-meters measure the change in rotation; accelerometers measure the rate of change in position; and displacement gages measure movement with respect to a fixed reference. Each of these instruments is limited to the specific location where it is placed. With these instruments, we are able to monitor how bridges strain and move under load in real time. Taking it one step further, engineers can do things such as evaluate local stresses at fatigue details, monitor earthquake accelerations, calibrate finite element models, or monitor real-time response as a super-load crosses a bridge.

A realization arose in the bridge evaluation community that there is a great opportunity

Structural monitoring can show real-time response to live loads.

to combine traditional inspection techniques and structural response monitoring to obtain a more complete picture of the health of a bridge. In one respect, inspection is still vital to grasp an overall evaluation of a bridge. A visual inspection by a trained engineer provides a wealth of information. However, a visual inspection can’t see the stress in a structural member under live load. It can’t see the out-of-plane transverse deflection. Moreover, an inspector can’t be on site for 24 hours a day, every day. On the other hand, SHM monitoring can indicate the stress in a member, and it can determine structural movement. But, as of today, it can’t provide an overall view of a bridge that a visual inspection can. So, in pairing the two, SHM becomes a rather powerful option for assessing the health of a bridge. It has become another tool in the engineer’s tool box. One of the best uses has been to verify structural live load response where the behavior is questionable or unknown (e.g. live load distribution).

There are other advantages to SHM beyond evaluating an instantaneous response to load. Long term monitoring can aid in event response. For example, what happens to a structure at the precise moment it incurs an extreme load? Engineers and owners might also be interested in long term monitoring to capturing a maximum response over a period of time, or to monitor the effects of weighin-motion traffic, or to capture a complete load history for a fatigue evaluation. If we have instruments in place to monitor long term response, we have the ability to capture an abnormal event such as a vehicle strike or an extreme overload. In a practical real-world example, a simple accelerometer was placed on a bridge because the owner thought it was getting struck by trucks bi-monthly, or so. They set an alert to be triggered every time there was a horizontal acceleration that exceeded a certain threshold, and snapped a picture of the event.

As it turns out, once the device was installed,

STRUCTURE magazine

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May 2014

the first e-mail alert went off the same night they activated the system. The alert message started firing once or twice a day, and provided evidence of each hit. Information like this can be vital in prioritizing decisions in a bridge management program.

But SHM isn’t always that simple. For example, SHM has the ability to create massive volumes of data without the ability to process what is being recorded. With a new flood of data, one of the most important advances for SHM will be the development of data management systems. Other industries have adapted self-learning computer programs, and the same should be done for long term monitoring for SHM. The type and level of instrumentation continue to evolve as well.

Fantastic techniques, like image correlation and adaptation of ground-penetrating radar, are opening up the possibilities of taking the aspects of a visual inspection and incorporating them digitally.

There are also possibilities to integrate SHM into our daily management of bridges.

According to Zee Duron, Engineering Department Chair of Harvey Mudd College “Engineers have got to get smarter about what the sensors are telling us, and we’ve got to get more politically astute in terms of how we take that information and turn that into economic and public policy that actually improves the infrastructure of the United States.” Conversely, John Fisher, Professor Emeritus at Lehigh University stresses instrumentation should be judiciously applied, “It has to be rationalized because, one, there’s a cost associated with it, and two, why make measurements if they’re not needed?”▪ Duncan Paterson, P.E., Ph.D., is a Professional Associate and Sr. Bridge Engineer with HDR Inc. in Cincinnati, OH.

InBox

letters to the editor

A

RINE ENG MA I

ETY OF NAV A CI O

RCHITECTS LA

&

• THE ERS S NE

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s a life-long San Francisco Bay Area resident, I was motivated to write this letter when I read the two articles published in the February 2014 issue regarding the San FranciscoOakland Bay Bridge. I found the articles topical and provocative. However, if we are to improve rush hour traffic through the San Francisco-Oakland-Berkeley corridor by considering the addition of a second identically configured parallel bridge adjacent to the existing one, I would have liked to have seen some of the more obvious questions/issues addressed: 1) Can the existing freeways at either end of the proposed second and existing bridges handle the greater number of vehicles on the two bridges so that the overall traffic situation would be improved?

2) What would be the cost of the new surface roadways, connector ramps and access points, and perhaps new freeways required to join to the new bridge? Where would these roadways be located and what would be the environmental impact (traffic, business, noise, views, etc.) on the cities of San Francisco, Oakland and Berkeley?

3) Assuming that the original 1930s bridge design was ideal, what would be the engineering and cost rationale for building a new bridge with re-used, archaic 1930s members, rather than just using new materials with an improved double deck configuration? Is it necessary to replicate the clear span of the Eastern span cantilever section?

4) Would it be practical and cost-effective to dismantle the existing bridge in such a manner as not to damage the individual elements, so that they could be stored and reconstructed later? e rat bo nce a l l e co peri p ex velo de end att rn lea are sh eet m n joi

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5) Since the original Eastern span is widely considered unattractive and a long-standing insult to the residents of the East Bay, would it be possible to get public support for its reconstruction?

I agree that the new Eastern span has not made the vehicular traffic situation any better; it actually seems worse now, if that is possible, and it is likely to get even worse in the future. But since the new Eastern span has just opened after 25 years of design and construction and at a huge cost to the taxpayers, not to mention the question of whether it was an appropriate or efficient engineering design, I must admit that adding another bridge in essentially the same place did not cross my mind. I have not really recovered from the last project. Besides, the concept of adding another cross-bay bridge south of San Francisco to the East Bay, also known as the “Southern Crossing,” has been studied in various alignments and locations since the 1940s, but consistently rejected.

As an alternative to more bridges and roadways, increasing the capacity and service area of the BART rail system deserves serious consideration as a means of reducing the demand on the existing Bay Bridge.

Maybe a Southern Crossing with shared vehicular and BART rail traffic could be part of a comprehensive traffic improvement plan. Some people like to ride ferries, but I think that the time for that technology, as a serious contributor to traffic capacity, is in the past, although it might play a small part in the future.

Before we consider a second Bay Bridge, we really need an in-depth study to flush out the best alternatives and the true costs.

John Dal Pino, S.E. jdalpino@degenkolb.com P.S. Saving the old Eastern span is really a moot point, since demolition is already underway.

Response to John Dal Pino’s “Letter to the Editor” These are all good points. We share the concerns raised by Mr. Dal Pino, and assume that various transportation agencies share them, too.

The combined factors of high costs and lengthy construction time devoted to replacing the east span have likely exhausted any public enthusiasm for an additional bridge. Even so, substantial increases in public transportation budgets will not provide adequate relief where it is most needed. A second underwater tube for BART, for instance, is unlikely to address the true nature of the congestion. The only viable solution is a second bridge.

We believe the challenges associated with a second crossing can be surmounted. While space does not allow us to expand on our ideas for why a parallel bridge has practical and economic advantages, we also readily acknowledge the potential for other viable bridge options. Ultimately, we believe that a multi-stage design competition would get the best ideas on the table.

Regardless of aesthetic preferences related to structural systems (steel truss vs. concrete viaduct), the fundamental question remains: “How long do we delay plans for an additional crossing, and at what ultimate cost?” We feel engineering professionals are better suited to tackling this question pro-actively, rather than waiting for it to make the agenda of elected officials.

Ronald F. Middlebrook, S.E. and Roumen V. Mladjov, S.E.

STRUCTURE magazine

38

May 2014

news and information

Noteworthy

John A. Mercer Jr. Retires from STRUCTURE ® Editorial Board

J

ohn A. Mercer Jr., P.E., is stepping down as a member of the STRUCTURE magazine Editorial Board. John joined the Editorial Board in December 2003 as a CASE representative. He is President of Mercer Engineering, PC, a structural engineering consulting firm located in Minot, North Dakota.

Jon Schmidt, P.E., SECB, Chair of the STRUCTURE magazine Editorial Board, had this to say on John’s departure: “John Mercer is one of the longest-serving members of the Editorial Board. It has been an honor and a pleasure to work with him throughout my time as chair, and we will all miss his valuable perspective.

I wish him the best as he continues to serve the profession in other ways.”

Regarding his tenure on the Board, John commented: “Serving the structural engineering community by participating and representing the Council of American Structural Engineers (CASE) on the Editorial Board of STRUCTURE magazine has been one of the highlights of my career. I’ve been privileged to meet and work with

some of the giants in our profession. People like Walter Hanson who authored one of my university texts on soils engineering is just one example. The team approach of CASE, NCSEA, and SEI in supporting STRUCTURE magazine undergirds my mantra, TEAMS WIN! individuals wither…

I want to thank you the reader, the article authors, and all of the members of the Editorial Board that I have been blessed to have worked with in making STRUCTURE magazine the best and most exciting periodical for structural engineers on the planet!”

John A. Dal Pino, S.E., will replace Mr. Mercer as one of three CASE representatives to the Editorial Board. Mr. Dal Pino is a Senior Principal at Degenkolb Engineers in San Francisco, CA. He is a licensed Structural Engineer in California with over 30 years of experience. John’s broad range of project work includes the design of new buildings, structural evaluation and strengthening of existing buildings in areas of high seismic hazard, renovation of historic buildings, deep excavation bracing and other construction-related activities,

John A. Mercer Jr., P.E.

John A. Dal Pino, S.E.

structural plan review and seismic peer review. John is a San Francisco native and has lived in the Bay Area his entire life.

Jon Schmidt said this about Mr. Dal Pino’s appointment: “I am happy to welcome John Dal Pino as the newest CASE representative on the Editorial Board. He has already hit the ground running, by submitting a letter to the editor that appears in this issue.”

Please join the STRUCTURE magazine Editorial Board in welcoming John Dal Pino.

book reviews and news

Bookcase

Reinforced Masonry Engineering Handbook Clay and Concrete Masonry, 7 th Edition (2012)

T

By David T. Biggs, P.E., S.E.

he handbook is jointly published by the Masonry Institute of America (MIA) and the International Code Council (ICC). Now in its seventh edition, the handbook continues to be a must-have reference for both structural engineers designing masonry and inspectors. The original author was James E. Amrhein, P.E., S.E. who continued developing the handbook until his passing in 2011. For the last two editions, co-authors have assisted Jim. This edition was capably co-authored by John M. Hockwalt, P.E., S.E. of KPFF Consulting Engineers, Seattle.

The MIA states that “The Reinforced Masonry Engineering Handbook (RMEH), 7th Edition, is based on the requirements of the 2012 IBC, 2011 Building Code Requirements and Specification for Masonry Structures (TMS402) and ASCE 7-10. The RMEH contains detailed explanations and applications of Allowable Stress Design and Strength Design procedures, more than 70 step-by-step examples, distribution and analysis for lateral forces, details of reinforcing steel and much more”.

Although the RMEH is not a textbook, many engineers (including this reviewer) learned

masonry design from Jim Amrhein and his handbook. The original editions were based upon the Uniform Building Code but are now based upon the TMS 402 and the IBC; so, the handbook is applicable to all structural engineers in the United States. It is clearly written with numerous tables and worked out examples.

All the chapters contain useful information, especially Chapter 3, Loads which includes lateral loads, wind and seismic. It also explains components and cladding loads for wind. Chapter 4 includes lateral distribution and diaphragms.

Another particularly useful feature is the highlighted sections within the text that address specific criteria of the TMS 402 and the IBC. Finally, there are also two case studies for a one-story industrial building (Chapter 11) and a seven-story masonry loadbearing wall apartment building (Chapter 12) that are rarely published in such detail.

The handbook has a companion CD that includes: 1) RMEH 7 th edition 2) Code Master, Allowable Stress Design for Masonry using the 2011 TMS 402 and 2012 IBC

STRUCTURE magazine

39

May 2014

3) Code Master, Strength Design for Masonry using the 2011 TMS 402 and 2012 IBC Structural engineers will find the Code Master documents provide a practical step by step design methodology. Masonry inspectors will also appreciate the handbook because the CD includes some handy references: 1) Reinforced Concrete Masonry Construction Inspector’s Handbook, 7 th Edition 2) Inspector’s Handbook for Reinforced Grouted Brick Masonry, 15th Edition 3) Reinforcing Steel in Masonry, Fifth Edition 4) Code Master, Masonry Materials using IBC 2006 5) Code Master, Special Inspection of Masonry using IBC 2009 Practitioners and someone taking the PE or SE exams will benefit from using the RMEH. It is available from the MIA, the ICC and The Masonry Society.▪ David T. Biggs, P.E., S.E., is with Biggs Consulting Engineering in Troy, NY. He is a Fellow of SEI, Distinguished Member ASCE, Fellow ACI, and Honorary Member of TMS. David may be reached at biggsconsulting@att.net.

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All Resource Guides and Updates for the 2014 Editorial Calendar are now available on the website, www.STRUCTUREmag.org. Listings are provided as a courtesy. STRUCTURE® magazine is not responsible for errors.

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May 2014

StructurePoint Phone: 847-966-4357 Email: info@structurepoint.org Web: www.StructurePoint.org Product: pcaMats-spMats Description: Analysis, design and investigation of concrete foundations, mats, combined footings, pile caps and slabs on grade.

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award winners and outstanding projects

Spotlight

For the Birds: Reimagining a Legacy

By Chris Olson, S.E. Dunn Associates, Inc. was an Outstanding Award Winner for the Tracy Aviary Visitors Center project in the 2013 NCSEA Annual Excellence in Structural Engineering awards program (Category – New Buildings under $10M).

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Early in the design process, the building exterior was completely concrete masonry units, for both gravity bearing and lateral load resistance. As the owner’s vision for the aesthetics of the building evolved, so did the exterior walls. In order to increase visitor’s and staff’s views, and increase the inviting nature of the building, more and more windows were added. Eventually enough windows were added that steel moment frames needed to be introduced. The varying lateral stiffness of each of these systems presented challenges in detailing. Correct expansion joints and slip conditions were required to make sure each of these lateral systems, as well as other architectural and mechanical systems, could accommodate the lateral drift.

One of the buildings most notable features is the custom metal façade that forms the skin. This was accomplished by using sheets of thin steel plates. The connections of plates to the building had to respect the variable nature of the building’s dual lateral system in addition to supporting their own gravity loads.

A light, airy exterior was architecturally desired and incorporated an abstract pattern that suggests a tree canopy and branches, while evoking a sense of motion. The metal panel system was held out, away from the exterior.

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May 2014

Green Building strategies include reduced energy consumption provided by a photovoltaic solar array on the roof, energy-efficient building systems which are 36% more efficient than a “baseline” building, extensive use of locally sourced and recycled materials, use of low-emitting products such as paint, adhesives, and flooring. In addition, 75% of construction waste was recycled.▪ Chris Olson, S.E., is a Principal Engineer at Dunn Associates, Inc. located in Salt Lake City, Utah. He may be reached at colson@dunn-se.com.

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he Tracy Aviary, located at Liberty Park, initiated a massive renovation that will completely transform its physical landscape and exhibits to renew its position as one of Salt Lake City’s prized assets. To begin this renovation, the Aviary needed a new multifunction facility. The building needed to house a visitor center, gift shop, ticketing and entrance facilities, staff offices and open classroom/ learning spaces. This building would truly be a focal point for families and patrons as they entered the grounds.

On the site, the Visitor’s Center and associated boardwalk frame a nearby pelican pond.

The soils are a combination of saturated loose sands and clays. These challenging soil conditions lead to a dual solution for the building and boardwalk. The building, at its closest only 5 feet away from the pond, was founded on a mat footing. Due to tight budget constraints, the thickness was varied around the perimeter. This allowed the higher loads at the masonry bearing walls and steel moment frames to be adequately resolved. As traditional spot footings would be too invasive to install in and near the pond, the surrounding boardwalk was supported by helical piers.

The Visitors Center’s plan is a gentle ‘Z’ form, weaving the building and visitor circulation through art, trees, and the Pelican Pond.

Connecting the two ‘L’ shaped wings that are arranged to form this ‘Z’ shape is a bridge, which covers the ticketing and visitor entrance to the Aviary. The bridge is rigidly connected to one wing and incorporates an expansion joint. This joint allows for both seismic induced lateral displacement and thermal expansion.

Interior spaces needed to be as open as possible to allow easy patron flow and possible future reconfiguration. To keep the floor plan open, the roof and floor framing spans from exterior to exterior. Composite wide flange beams form the floor framing. The roof is steel open web joists.

GINEERS

2014 NCSEA Excellence in Structural Engineering Awards Highlighting the best examples of structural engineering ingenuity throughout the world

May 22, 2014 Fire Resistance of Concrete, Masonry & Timber Nestor R. Iwankiw, Ph.D., P.E., S.E., Senior Engineer, Hughes Associates, Inc.

Eight categories: • New Buildings under $10M • New Buildings $10M to $30M

June 5, 2014 The Analysis of Offset Diaphragm and Shear Walls Terry Malone, S.E., WoodWorks

• New Buildings $30M to $100M • New Buildings over $100M • International Structures • Renovation/Retrofit Structures

June 17, 2014 Practical Design of Complex Stability Bracing Configurations Donald White, Ph.D., Professor, Georgia Institute of Technology, School of Civil and Environmental Engineering

• Other Structures • New Bridges/Transportation Structures

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Entries are due Friday, July 11, 2014, and awards will be presented at the NCSEA Annual Conference September 19 in New Orleans.

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Eligible projects must be substantially complete between January 1, 2011 and December 31, 2013.

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NCSEA News

May 16, 2014 CalOES Safety Assessment Program (full day webinar, not included in subscription plan) Jim Barnes, C.E., California Governor’s Office of Emergency Services

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News form the National Council of Structural Engineers Associations

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NCSEA Webinars

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Diamond Reviewed

Non-CalOES courses 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.

NCSEA offers three options for registrations to NCSEA webinars: Ala Carte, Flex-Plan, and Yearly Subscription. Visit www.ncsea.com for more information or call 312-649-4600.

NCSEA Annual Conference Astor Crowne Plaza Hotel, in the heart of the French Quarter New Orleans, LA

September 17-20 2014 Featuring: • Structural Engineering Education • Trade Show • Awards Banquet, including the NCSEA Excellence in Structural Engineering Awards and the NCSEA Special Awards

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May 2014

The second NCSEA Winter Leadership Forum drew principals and leaders from a diverse group of engineering firms to Napa, California for thought-provoking sessions, meaningful interaction, and networking. Sessions focused on ownership transitions, the effect of delayed retirements, maintaining client relationships, and conflict resolution, and finished with an interactive case study on risk and claim management. Attendees enjoyed the wonderful weather and a wine-tasting reception at the Meritage Resort’s Estate Wine Cave. For more photos and comments, visit www.ncsea.com.

NCSEA News

Napa Valley Draws Leaders and Principals for Education and Networking at NCSEA Winter Leadership Forum

News from the National Council of Structural Engineers Associations

“This was the first major NCSEA event that I have attended, and I found it very interesting and enjoyable. The topics discussed were all of interest to me, and the speakers were knowledgeable and kept us engaged. I look forward to the next conference.”

Jay Shapiro, P.E. Howard I. Shapiro & Associates

Engineers from the following firms were represented at the 2014 NCSEA Winter Leadership Forum: ADR Systems of America ARW Engineers Barter & Associates BFMJ, INC BHB Consulting Engineers DCI Engineers Degenkolb Engineers Dibble Engineers, Inc. DiBlasi Associates FMI Corporation GEI Consultants, Inc. Gilsanz Murray Steficek Haskell Howard I. Shapiro & Assoc.

IBI Group Michigan Jose I. Guerra, Inc.

Joshua B. Kardon + Co. KL&A, Inc. Martin/Martin, Inc. Nayyar & Nayyar PCS Structural Solutions Peak Engineering Inc. SESOL, Inc. Severud Assoc. Cons. Engrs Simpson Gumpertz & Heger Sound Structures, Inc Stantec Summit Engineering Thornton Tomasetti Wallace Engineering Wright Engineering

Thanks to our platinum level sponsors:

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Ed DePaola, P.E., SECB, F.SEI, M.ASCE Severud Associates Consulting Engineers

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“I enjoyed the interactive format and the lively discussions from diverse perspectives. Well worth my time.”

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Get Involved In Your Local SEI Chapter

Structural Columns

The Newsletter of the Structural Engineering Institute of ASCE

SEI Hawaii Chapter

West Virginia SEI Graduate Student Chapter

The SEI Hawaii Chapter’s first event was held on March 6 at the Ka’Ikena Tamarind Room at Kapiolani Community College in Honolulu. This meeting was organized jointly with the Structural Engineers Association of Hawaii (SEAOH), ASCE Hawaii Chapter, and our newly formed Structural Engineering Institute Hawaii Chapter. It was very well attended by more than 60 structural, civil and geotechnical engineers. Our featured speaker was Steven Baldridge, P.E., S.E., LEED AP, President of Baldridge & Associates Structural Engineering, Inc. Steve shared his insights on the latest high rise projects in Honolulu and how they tie to transit oriented development (TOD). He also highlighted some of the impressive high rise projects his firm has been working on in India, including Wave One and Wave Virtue. Wave One is a 44-story structure with two towers jointed at the top eight floors. Combined, Wave One and Wave Virtue are approximately 4.8 million square feet of mixed use space. Steve highlighted differences between the U.S. and India structural requirements with respect to design codes and loading.

In India, heavier finishes are used and dramatic depressed slabs for architectural requirements have a significant impact on the structural system. His presentation brought an interesting and often amusing perspective on the opportunities and challenges of working in developing economies.

ASCE Sustainability Project Award With the growing importance of sustainability as a critical performance factor in civil engineering projects, ASCE established the Innovation in Sustainable Engineering Award, honoring a project that demonstrates innovations in sustainability. Nominated projects are evaluated on the basis of: (a) the extent to which innovative design or construction methods improve economic, social and environmental sustainability; (b) the potential to promote future developments in sustainability; (c) the degree to which the project extends public understanding of sustainability in engineering and construction. Projects developed or implemented between 2007 and 2013 that have not been a candidate for the Outstanding Civil Engineering Achievement (OCEA) Award are eligible for consideration. Entries are due to the Honors and Awards Program office by June 1, 2014. For award details and downloadable entry form visit www.asce.org/awards. To submit an entry or to request assistance, contact awards@asce.org.

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The Structural Engineering Institute Graduate Student Chapter at West Virginia University provided hands-on activities and demonstrations to several visiting High School students from all over the state (WV) on Saturday, February 22, 2014. The activities included concrete mixing, compression testing of concrete cylinders, a presentation on Fiber Reinforced Polymer (FRP) composites for civil infrastructure, and a live demonstration of infrared thermography for defect detection in composite bridge decks.

Become Involved in Local Activities Join your local SEI Chapter or Structural Technical Groups (STG) to connect with colleagues, take advantage of local opportunities for lifelong learning, and advance structural engineering in your area.

If there is not an SEI Chapter or STG in your area, talk with your ASCE Section/Branch leaders about the simple steps to form an SEI Chapter.

Some of the benefits of forming an SEI Chapter include: • Connect with other SEI local groups through quarterly conference calls and annual conference • Use of SEI Chapter logo branding • SEI Chapter announcements published at www.asce.org/SEI and in SEI Update • One free ASCE webinar (to $299 value) sponsored by the SEI Endowment Fund • Funding for one representative to attend the Annual SEI Local Leadership Conference to learn about new SEI initiatives, share best practices, participate in leadership training, and earn PDHs. • SEI outreach supplies available upon request Visit the SEI website at www.asce.org/SEI for more information on how to connect with your local group or to form a new SEI Chapter.

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.

May 2014

2015 Structures Congress is scheduled for April 23-25, 2015 at the Portland, Oregon Convention Center. Schedule Changes: In response to attendee feedback all committee meetings will take place on Wednesday, April 22, 2015. This change will eliminate the schedule conflicts between committee meetings and technical sessions.

2016 Joint Congress with the GEO Institute will take place in February 2016. Dates and location are not finalized.

Special Joint Event: The 2016 congress will feature a total of 15 concurrent tracks: 5 tracks will be on traditional GI topics, 5 tracks on traditional SEI topics, and 5 tracks on joint topics.

In addition, we will be offering interactive poster presentations within these tracks.

What this means for you? Start thinking about sessions that would be of interest to both Geotechnical and Structural Engineers and prepare your session proposals.

Electrical Transmission and Substation Structures Conference 2015 Branson, Missouri September 27 – October 1, 2015

Featured Structural Webinar Live Webinars are ASCE’s high-impact training solution delivered by leading experts, with minimal disruption to your workflow. With ASCE Live Webinars you can train an entire group of engineers with a single registration fee, and all participating engineers can earn PDHs and obtain certificates at no additional cost.

May 20, 2014 Seismic Evaluation and Retrofit of Unreinforced Brick Masonry Buildings Using ASCE 41-13 Fred Turner, P.E., SECB The evaluation and retrofit of buildings with unreinforced masonry (URM) brick bearing walls is a significant part of the ongoing effort to improve existing structures in areas subject to earthquake hazard. This webinar introduces the requirements of Chapters 11 – Masonry, 13 – Architectural, 15 – System-Specific Performance Procedures, and 16 – Evaluation Checklists of ASCE 41-13 “Seismic Evaluation and Retrofit of Existing Buildings” for URM brick bearing wall buildings. The new standard provides a unified method for evaluating and retrofitting existing buildings for earthquakes, and eliminates significant inconsistencies between the two previous standards. For more information about this and other structural webinars see the ASCE website at: http://www.asce.org/Continuing-Education/Webinars/ Live-Webinars/.

STRUCTURE magazine

Portland, Oregon, April 23-25, 2015

CALL FOR PROPOSALS Submit your abstract and/or full session proposal today for Structures Congress 2015.

SEI is currently accepting proposals for complete sessions and abstracts for individual papers to be presented at Structures Congress 2015.

The Structures Congress provides a forum to advance the art, science, and practice of structural engineering. Proposals should focus on topics consistent with the list below. Topics include: Bridges and Transportation Structures Buildings Nonbuilding and Special Structures Nonstructural Systems and Components Natural Disasters Research Education Business and Professional Practice Blast and Impact Loading and Response of Structures All proposals are due June 11, 2014.

Visit the Structures Congress website for details about abstract and session proposals www.structurescongress.org.

Seismic Evaluation and Retrofit of Existing Buildings – ASCE 41 The next cycle to update ASCE 41 Seismic Evaluation and Retrofit of Existing Buildings kicked off on March 21, 2014.

Those who wish to participate in the standards update are encouraged to fill out an application on the SEI website at: www.asce.org/codes-standards/applicationform/, and to contact the committee chair Bob Pekelnicky (RPekelnicky@ degenkolb.com) about what subcommittee they would like to participate on.

The subcommittees are: General Provisions & Seismic Hazards Tier 1 Screening Tier 2 Requirements Analysis Geologic, Foundations, and Soil-Structure Interaction Steel Concrete Masonry Timber Cold Formed Steel Seismic Isolation and Supplemental Energy Dissipation Material Testing & Condition Assessment Nonstructural Provisions

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May 2014

The Newsletter of the Structural Engineering Institute of ASCE

Save the Date

Structures Congress 2015

Structural Columns

Important Information about the 2015 and 2016 Structures Congresses

The Newsletter of the Council of American Structural Engineers

CASE in Point

Books for Engineers CASE 962D–A Guideline Addressing Coordination and Completeness of Structural Construction Documents (Updated in 2013!)

CASE 962E–Guidelines for the Performance of Site Visits

The guidelines presented in this document will assist the structural engineer of record (SER), and also everyone involved with building design and construction, in improving the process by which the owner is provided with a successfully completed project. Their intent is to help the practicing structural engineer understand the importance of preparing coordinated and complete construction documents, and to provide guidance and direction toward achieving that goal.

These guidelines focus on the degree of completeness required in the structural construction documents (“Documents”) to achieve a “successfully completed project”, and on the communication and coordination required to reach that goal. They do not attempt to encompass the details of engineering design; rather, they provide a framework for the SER to develop a quality management process.

Co-authored by ten professional engineers on the CASE National Guidelines Committee, Guidelines for the Performance of Site Visits is a guide intended for the younger engineer but will be useful for engineers of all experience levels. Structural engineers know that site visits are crucial construction phase services that help clarify and interpret the design for the contractor. Site visits are also opportunities to identify construction errors, defects and design oversights that might otherwise go undetected. Engineers should include adequate construction phase services as a part of their scope of services to insure the design intent is properly implemented.

You can purchase all CASE products at www.booksforengineers.com.

Follow ACEC Coalitions on Twitter – @ACECCoalitions.

CASE Winter Planning Meeting Update On February 20-21, the CASE Winter Planning Meeting took place in Dallas, TX. CASE does two planning meetings a year to allow their committees to meet face to face and interact across all CASE activities. Over 30 CASE committee members and guests were in attendance, making this another well attended and productive meeting. During the meeting, break-out sessions were held by the CASE Contracts, Guidelines, Membership, Toolkit, and Programs & Communications Committees.

The committees finalized the schedule of new products for released in 2014, plus reviewed current documents for revisions; finalized speakers/sessions for the 2014 ACEC Fall Conference October 22-25 in Hawaii, and the 2015 ASCE/SEI Structures Congress scheduled for April, 2015 in Portland, OR. Again at this meeting, a roundtable session was held the night before with several topics including specialty licensure, social media, BIM and special inspections up for discussion.

Prior to this roundtable discussion, the CASE Executive Committee met and finalized plans for the next year.

The CASE Summer Planning Meeting is scheduled for August 5-6th in Chicago. The night of August 5th will feature a speaker from Willis talking about ways to manage your STRUCTURE magazine

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firm’s risk. If you are interested in attending the meeting, or have any suggested topics for the committees to pursue, please contact CASE Executive Director Heather Talbert at htalbert@acec.org.

CASE Member Firms Win Honor Awards Congratulations go out to the following CASE Member, firms recently awarded Honor Awards at the ACEC Engineering Excellence Gala: Degenkolb Engineers of San Francisco, CA for its project, Bing Performance Arts Center, Stanford University in Palo Alto, CA Thornton Tomasetti of New York, NY for its project, Barclays Center in Brooklyn, NY Weidlinger Associates, Inc. for its project Brooklyn Botanical Garden Visitor Center in Brooklyn, NY

May 2014

20 th Senior Executives Institute Class Now Open For Registration

ACEC has developed the new quarterly Engineering Business Index (EBI) survey to serve as a leading economic indicator for the engineering industry.

Produced in conjunction with FMI – a provider of research for the engineering industry – the quarterly EBI will generate unique data on industry performance and market trends.

Member Firm CEOs received their first EBI survey inquiry this week. The survey takes no more than three minutes to complete and all responses are confidential.

For further information, contact ACEC Director of Communications Alan D. Crockett (acrockett@acec.org).

Upcoming ACEC Online Seminars – June Simple Revenue Boosters to Start Now

June 3, 2014; 1:30pm to 3:00pm How do you communicate your value in ways that directly impact your bottom line? www.acec.org/education/ eventDetails.cfm?eventID=1523

How to Give and Receive Effective Feedback – Improving Your Mental Flexibility or Change Your Thinking About the Way You Think – Spring 2014

June 10, 2014; 1:30pm to 3:00pm Improve your communication skills by learning how to give and receive feedback. www.acec.org/education/eventDetails. cfm?eventID=1559

Positioning to Win: Taking QBS to the Next Level

June 17, 2014; 1:30pm to 3:00pm Learn how to get your firm from the short list to the contract. www.acec.org/education/eventDetails.cfm?eventID=1544

Writing Proposal Sections

Industry Economic Update: What Can We Expect for the Second Half of 2014?

June 19, 2014; 1:30pm to 3:00pm Learn how to adjust your 2015 firm goals and strategies based on economic and trend forecasts. www.acec.org/education/ eventDetails.cfm?eventID=1554

Dare To Be Different! Developing a Differentiation Strategy, The Key to Your Competitive Advantage

June 24, 2014; 1:30pm to 3:00pm With short lists getting longer and competition more intense, learn how to make your firm stand out and win the project. www.acec.org/education/eventDetails.cfm?eventID=1570

Strategies for Managing Interruptions: Getting Work Done in an Interrupted World

June 25, 2014; 1:30pm to 3:00pm How can you better manage interruptions, limit distractions from them and still be responsive to key stakeholders, customers and co-workers?

June 18, 2014; 1:30pm to 3:00pm Roll up your sleeves and get into the nitty gritty of how to write effective cover letters, statements of understanding, project approaches, scopes of service, resumes, and project histories. www.acec.org/education/eventDetails.cfm?eventID=1589 STRUCTURE magazine

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May 2014

CASE is a part of the American Council of Engineering Companies

For 20 years, ACEC has offered the premier executive leadership course designed specifically for the A/E/C community – the ACEC Senior Executives Institute (SEI). SEI is an intensive 18-month program taught by recognized experts and instructors from The Brookings Institution, national universities and business consulting organizations. The classes meet for five separate four or five-day sessions.

The next class, SEI Class 20, is now open for registration and will begin in September, 2014.

For more information, contact Dee McKenna, Deputy Director, ACEC Business Resources & Education Department, at dmckenna@acec.org or 202-347-7474.

ACEC Launches New Engineering Business Index

CASE in Point

ACEC Business Insights

Structural Forum

opinions on topics of current importance to structural engineers

Training the Structural Engineer Part 2

By Stan R. Caldwell, P.E., SECB

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nlike the students aspiring to enter many other professions, structural engineering students in most states are not permitted to take their licensing examinations immediately upon graduation. Rather, they must first serve an apprenticeship of three or four years. During this period, they typically have titles such as Engineer-In-Training (EIT), Engineering Intern, or Graduate Engineer.

By state law, EITs are required to perform engineering work only under the direct supervision of licensed professional engineers.

Ideally, EITs are exposed to a wide range of projects, from simple to complex, from modest to massive, from new construction to long-overdue renovation, and from their local communities to overseas. They are given the opportunity to work with many different construction materials and frequently visit jobsites to observe ongoing construction. In the office, they become immersed in their firm’s structural analysis and design process, from concept through completion. They learn the role of structural engineers, both within their firms and within their project teams.

Mentoring is arguably the most important aspect of workplace training. This is the process by which young engineers are actively coached by the experienced engineers around them. It is a critical process, because it is the only way that knowledge and wisdom are effectively passed from one generation to the next. Good mentors are able to develop close relationships with their EITs. They act as friends, advisors, teachers, coaches, cheerleaders, and in some respects, even as parents.

EITs generally want more guidance, but senior engineers are often reluctant to provide it under the pressure of tight project budgets and schedules. “My door is always open,” is a popular approach to mentoring, but is not always viable.

Many EITs hesitate to “waste” the time of senior engineers or risk the perceived embarrassment of asking dumb questions. Formal mentoring programs attempt to ensure authenticity by pairing EITs with senior engineers, and holding both parties accountable for frequent and meaningful communication.

Prior to licensure, EITs are expected to tackle ever-increasing engineering challenges and responsibilities, to gain confidence in their abilities, and to earn the confidence of others.

Was this your experience as an EIT? What about the EITs who now report to you? Are these outcomes usually achieved in your firm and elsewhere? Very few structural engineering employers have training programs that consistently succeed, and the ones that do tend to be relatively large organizations. Smaller firms, which represent the vast majority of structural engineering employers, present quite a different picture.

Many structural engineering firms attempt to provide EIT training, but lack the project diversity or organizational resources necessary for it to be effective. Other firms put little thought or effort into EIT training and often assign their EITs to menial and repetitive tasks. Unfortunately, some firms simply view EITs as a source of relatively inexpensive and easily disposable labor. They keep the best and cut the rest. In summary, there is no standard workplace training experience today for EITs. As Forrest Gump might say, the situation is like a box of chocolates: “You never know what you’re gonna get.”

Last year, SEI and NCSEA jointly asked 10,065 structural engineering leaders to participate in an online survey of the profession.

The survey was lengthy, but 352 engineers, a respectable 3.5%, agreed to participate. Of these, 48% represented firms with less than 25 employees and 84% represented firms with 25 or fewer structural engineers. About 50% described their employers as structural engineering design firms, and 88% classified themselves as being in the private sector.

Additional information on the survey can be found in Appendix A of A Vision for the Future of Structural Engineering and Structural Engineers: A Case for Change. This must-read SEI report is available as a free download at www.asce.org/SEI. With respect to workplace training, the survey results are not encouraging. Only 15% reported that they have formal mentoring programs, and 34% reported no mentoring

of any kind. Slightly more than 80% reported that they support workplace training, mostly in-house, but also online and out-sourced.

However, 75% of such training addresses the technical skills intended to increase productivity, and only 25% targets the so-called “soft” skills that are necessary to support career growth. Only 40% reported that they maintain a specific budget for training.

Not surprisingly, 75% concluded that their approach to training needs improvement.

There must be a more productive and consistent way to train and mentor young engineers prior to licensure. One radical concept is based on “The Teaching Hospital Model.” In this adaptation, leading structural engineering firms will agree to serve as “teaching firms.” Working through a professional organization such as SEI or NCSEA, they will create a standardized program to train, mentor, and monitor the progress of the EITs in their workplaces. This organization might also serve as a clearinghouse to distribute new graduates to the teaching firms based on merit, location, and other considerations.

Teaching firms will compensate their EITs fairly, in accordance with their various policies, but may or may not become the permanent employers of the EITs whom they train. In turn, an EIT might work for more than one teaching firm prior to taking the licensing exam. In fact, in an ideal situation, an EIT might spend one year with a U.S. bridge design firm, another with a foreign structural engineering firm, and a third with a U.S. building design firm. That EIT would be uniquely trained and almost certainly would be highly valued by structural engineering employers.▪ Stan R. Caldwell, P.E., SECB (www.stancaldwellpe.com), is a consulting structural engineer in Plano, Texas. He currently serves on the SEI Board of Governors, SEI Futures Fund Board of Directors, SECB Board of Directors, and SELC Steering Committee.

The focus of this two-part article is on training the future structural engineer prior to licensure. Part 1, which appeared in the April 2014 issue, addresses training in the classroom and laboratory.

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.

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May 2014