STRUCTURE magazine - August 2020

STRUCTURE AUGUST 2020

NCSEA | CASE | SEI

STEEL/CFS

INSIDE: The Conrad Washington, DC

22

Steel Connections Building with Shipping Containers Round HSS Essentials

14 26 28

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EDITORIAL STAFF Executive Editor Alfred Spada aspada@ncsea.com

Publisher Christine M. Sloat, P.E.

In Part 1 of the series of articles on Antiquated Structural Systems (September 2007, Engineers Notebook, pg. 46) the formula for Unit A was written as 2As fs = 2(M1/jd ), when in fact it should have been 2As fs = (M1/jd ) per the referenced 1918 ACI document. The Unit C Column Head equation should read: 2As fs = 0.64(M/jd ). Both equations have been corrected in the online PDF of the article. If you are using this series as a reference, please update your copy. The author would like to thank Michael F. Hughes, P.E., S.E., for discovering these errors.

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Contents AU GUST 2020

22 FROM THE TOP DOWN

Cover Feature

By Chris Crilly, P.E., et. al

For the Conrad Washington, DC, a tight complicated site, large column-free ballrooms, and a below-grade loading dock compelled the team to selectively use structural steel in a predominantly concrete structure to solve design challenges. An advanced analysis was necessary to provide an optimal building structure.

26 SAFE BUILDING WITH SHIPPING CONTAINERS

By Stephen Shang

The future of a well-defined shipping container building code is becoming a reality. Container-based structures can help in solving affordable housing in major urban areas or extra space in overcrowded schools. The adoption of new guidelines will ensure that each container structure is safe.

Columns and Departments 7

Editorial United in Action

28

By Emily M. Guglielmo, S.E., P.E.

8

Structural Design Structural Considerations

By Kim Olson, P.E.

32

12

14

Structural Modeling Steel Connections

By Martin Vild, Ph.D., František Wald, Ph.D., and Lubomír Šabatka, Ph.D.

18

36

Structural Connections Modern Wood Fasteners – Part 1

By Alex Salenikovich, Eng., Ph.D., David Moses, P.E., Ph.D., and Marcel Hong, EIT

August 2020 Bonus Content

Structural Forum On the PATH to S.E. Licensure

By Brian Falconer, P.E., S.E., SECB

Structural Forensics Why Did It Crack?

By Elizabeth Mattfield, P.E.

Education Issues Used the Most, Taught the Least

By John Lawson P.E., S.E., Michelle Kam-Biron, P.E., S.E., and Brent Perkins, P.E., S.E.

for Openings in Composite Floor Decks

By Natasha Zamani, Ph.D., P.E.

Structural Components Round HSS

42

Business Practices Speed Kills

By Joseph Tortorella, P.E.

In Every Issue 4 35 39 40 41

Advertiser Index Resource Guide – Software NCSEA News SEI Update CASE in Point

Additional Content Available Only in the Digital Magazine – STRUCTUREmag.org

Feature The City Creek Center's Brick Masonry Façade By John G. Tawresey, S.E. InSights ASTM A913 Quenched and Self-Tempered Structural Shapes By Shane Vernon, P.E. Legal Perspectives Best Practices By Brett Stewart Publication of any article, image, or advertisement in STRUCTURE® magazine does not constitute endorsement by NCSEA, CASE, SEI, the Publisher, or the Editorial Board. Authors, contributors, and advertisers retain sole responsibility for the content of their submissions.

AUGUST 2020

5

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EDITORIAL United in Action

By Emily M. Guglielmo, S.E., P.E., F.SEI

S

ome professional associations struggle to find social relevance, • Collaboration with the NCSEA Structural Engineering and optimally serve their membership. These difficulties are Engagement and Equity (SE3) committee to report on often the result of an inability or unwillingness to take action, the additional dimensions of diversity, equity, and inclusion and inclination to speak in silos, and the lack of aligned partners. Today’s evaluate new initiatives and programs; unprecedented pace of technological, social, and generational disruption particularly challenges these organizations.

We can cling to past successes and I strongly believe our structural engineermanage the status quo, or we can embrace ing associations are outliers to this traditional approach. CASE, NCSEA, and SEI recognize today’s disruption as an opportunity the enormous opportunities associated with a unified vision, coupled with joint action. The to create transformative change for our 2019 Joint Vision for the Future of Structural Engineering was the first tangible result of this associations and our profession. partnership. In this document, the three organizations envisioned a future in which structural engineers are widely recognized as vital contributors to the advancement • Partnering with the National Society of Black Engineers of society. The ongoing collaboration demonstrates a commitment to (NSBE) to identify and support mechanisms to increase the using a uniform voice to implement change across our profession’s diversity and quantity of engineers entering the structural spectrum, from licensure to leadership training, from mentorship to engineering profession. messaging, from public perception to policy development.

Real change takes significant commitment, persistence, and intenDespite these efforts, our communities and our profession are suffer- tion. With this in mind, NCSEA developed an action plan that sets ing from the expanding COVID pandemic, the subsequent economic the framework for a long-term commitment to diversity, equity, and crisis, and the effects of long-term racial injustice. However, we have a inclusion. We need your voice and active participation to advance choice in our response to these stressors. We can cling to past successes diversity, equity, and inclusion initiatives and fight racial injustice. and manage the status quo, or we can embrace today’s disruption as I firmly believe that our associations and the structural engineering an opportunity to create transformative change for our associations profession are well-positioned to positively impact our communities and contribute to a better future for all. and our profession.

Structural engineers are recognized leaders in supporting our commuThe expansion of our professional and societal influence does not mean nities following natural and man-made disasters, such as earthquakes, that our associations will cease traditional offerings, such as continuhurricanes, and terrorist attacks. At this moment, we have an oppor- ing education, professional networking, and licensure advancement. tunity to embrace our record of proven leadership to provide support However, the structural engineering profession has historically struggled and action in response to longstanding racial injustice and inequity. to achieve visibility, to influence public policy meaningfully, or to As we survey our own demographic, it is starkly apparent that our advocate for our profession. Embracing today’s challenges will result structural engineering profession does not reflect the diversity of the in new skills, audiences, and partners to not only advance diversity, communities we serve. equity, and inclusion in our profession but also improve our stature in Last month, CASE, NCSEA, and SEI jointly issued a Call to Action the broader community. to denounce racism and commit to furthering diversity, equity, and As we strive for these more aspirational and impactful societal and inclusion (DEI) in our organizations and the profession. While these professional goals, we realize that our voice must be loud, unified, powerful words represent a critical step to establishing a vision and and externally focused. More importantly, if we expect the public to a commitment to accountability, it is actions that lead to meaning- listen when we speak about safer structures, improved public policy, ful progress. With this fact in mind, NCSEA has publicly pledged or the value of our profession, we must also be willing to listen and to several actionable DEI goals. While our actions are currently in respond to our communities’ discussions. various stages of completion, NCSEA has made substantial progress Whether developing public policy, delivering consistent advocacy, with the following initiatives: or supporting social change, the commitment to progress must • Participation with SEI and CASE in the newly formed joint be consistent and present at all levels. I call on you, my CASE, committee to improve professional equity and opportunity; NCSEA, and SEI colleagues, to join me in bold, active, • Compilation and sharing of resources regarding racism, disand collaborative actions to transform our profession and crimination, and equity in the AEC industry; better serve our communities.■ • Preparation for unconscious bias training for all NCSEA leadership, including Board, Staff, and Committee Chairs; Emily M. Guglielmo is a Principal at Martin/Martin Consulting Engineers • Planning for a program focused on racism, equity, and social and the President of NCSEA. justice in structural engineering; STRUCTURE magazine

A U G U S T 2 02 0

7

structural DESIGN Structural Considerations for Openings in Composite Floor Decks

By Natasha Zamani, Ph.D., P.E.

C

omposite floor deck construction has become very popular. It combines structural efficiency with a speed of construction that offers an

economical solution for a wide range of building types, including commercial, industrial, or residential buildings. Composite slabs consist of profiled steel decking with an in-situ reinforced concrete topping. The decking not only acts as a permanent formwork to the concrete but also provides sufficient shear bond with the concrete so that, when the concrete has cured, the two materials act together compositely to resist the loads on the deck.

Openings in composite floor decks are a common part of any building. These openings can range from small holes for pipes and conduits to larger openings for mechanical ductwork, storm drain pipes, or a group of small holes. These openings allow contractors to install relevant building systems such as heating, ventilation, and plumbing.

Openings can have a significant impact on the structural performance of decks. It is essential that all openings are examined by a professional engineer to determine their influence on the deck and whether reinforcement around the opening is needed.

This article provides an overview of the various methods of creating small and medium-sized penetrations and their impact on the structural performance of composite decks.

Creating Openings There are two main methods to create small and medium openings in composite floor decks: core-drilling holes and sleeving or boxing-out openings.

Concrete core drilling involves drilling rounded holes in concrete walls or floors (Figure 1). Diamond concrete-core drills are the most commonly used tools for this process. The core drill bit tends to consist of a steel tube with a matrix impregnated with diamond segments welded to the drilling end. The concrete coring bit is mounted on a rotating shaft of a concrete core-drilling machine and

Figure 2. Schematic configuration of sleeving and boxing-out openings.

8 STRUCTURE magazine

Figure 1. An example of core- drilling of a concrete floor.

is secured to the wall or floor. A solid cylindrical concrete core or “slug� and metal deck under the cured concrete are removed from the hole once the drilling is complete. Due to the possible close spacing of existing floor slab reinforcement, reinforcement could likely be unintentionally cut during this process. Therefore, the location of the holes and the reinforcement should be coordinated with the structural engineer before coring. A scanner can be used to help locate the existing reinforcement steel to assist in avoiding it during the coring operation.

Sleeving or boxing-out is another approach to creating an opening.

In this method, the opening is formed by setting sheet metal sleeves in the deck (Figure 2). Alternatively, there are some cast-in firestop systems, including firestop cast-in sleeves, that can improve and simplify the entire installation process and increase the productivity and efficiency of contractors. Check with your local regulations and project requirements on whether it is permissible to cut the deck. The Steel Deck Institute (SDI), Manual of Construction with Steel Deck (SDI-MOC3), provides some examples of decked over floor opening closures, as illustrated in Figure 3.

It is highly recommended to leave the steel deck intact until the concrete has cured. However, contractors may cut the opening through the steel deck before the concrete is poured; they see this as a more straightforward installation with less labor, allowing immediate access to the openings before the concrete is poured. However, cutting out the slab before the concrete is cured can prevent the deck from properly

acting as a form. The steel deck must be examined by a professional engineer to determine if additional steel elements or temporary shoring are needed.

INTRODUCING

ADVANT

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deck-slab systems reflects the engineering concepts used to design reinforced concrete beams. The concrete acts as the compression material and the steel deck bonded to the bottom of the concrete acts as the tension reinforcing steel. The bending capacity of General Design the composite steel deck must be sufficient Information to resist out of plane gravity loads on the Composite floors consist of a condeck, which are typically superimposed crete topping cast onto a metal deck. dead and live loads in addition to the conThe topping can be light-weight or crete and deck self-weight (Figure 4 ). normal-weight concrete. The steel Composite decking is also used as a horideck is a cold-formed corrugated steel zontal shear diaphragm to stabilize the sheet that spans between steel joists or building and to transfer in-plane shear beams and serves a dual purpose. It loads (such as wind and seismic forces) serves as a form during the constructo the building’s main frame lateral resistion phase while the concrete is poured tance system (Figure 5, page 10 ). For this and cured and serves as reinforcement purpose, the composite deck shear diato act compositely with the concrete phragm is modeled as a horizontal beam to support the floor loads. Therefore, Figure 3. Decked over floor opening closure example. with interconnected floor deck units that Courtesy of SDI-MOC3. there are two main structural funcact as the beam web. Intermediate joists or tions to be considered for the design beams function as web stiffeners, and the of composite decks; (a) design the steel perimeter beams act as the beam flanges. deck as a form to support construction A detailed design guide can be found in loads, and (b) design the composite the Steel Deck Institute’s (SDI) Diaphragm slab for superimposed floor loads after Design Manual, Edition 4 (SDI-DDM04). the concrete hardens. However, the Due to the complexity of the design prodesign of the steel deck to serve as a cedures of composite floor decks, deck form is usually more critical than the manufacturers usually provide tables summadesign of the composite floor to suprizing permissible loads, section properties, port superimposed floor loads. The maximum unshored spans, superimposed steel deck profile and thickness need Figure 4. Out of plane gravity loads on the deck. loads, and diaphragm shear loads. However, to be chosen such that the unshored these tables consider the deck as a solid unispan of the steel deck can support the construction loads. form platform with no openings or penetrations. Since openings As a formwork during concreting, the steel deck should be designed can impact the deck performance, the engineer must independently to resist anticipated construction loads. This design must meet examine the penetrations and their effects on deflection, bending, the minimum design loads specified in the American National and shear strength of the deck to determine if reinforcement for the Standards Institute’s and the Steel Deck Institute’s Standard for deck is needed. continued on next page Composite Steel Floor Deck-Slabs, ANSI/ SDI C-2017. It also must evaluate three separate load combinations: (a) the dead weight of concrete and steel deck U.S Patent No. 10,570,618 plus a 20 pound per square foot (psf ) uniform construction live load, (b) the dead weight of concrete and steel deck plus a 150 pounds (lb.) concentrated Eventually There is load per foot width of the deck, and (c) the dead weight of steel deck plus a BETTER idea... not less than 50 pounds per square foot (psf ) uniform construction live load.

The engineer should also check the deflection of the deck at the construction stage to limit excessive deflections, which can lead to ponding of the con LIGHTER than traditional crete. Ponding can cause unintended floor systems dead load on the structure.  FASTER installation After the concrete is poured and cured,  LESS COST versus the deck acts compositely with the traditional bar joist/ concrete to resist superimposed loads. concrete and existing Cold Composite action is obtained by the www.advantsteel.com Formed Truss Systems shear bond between the concrete and the deck. The design of composite steel

AUGUST 2020

9

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shear capacity locally around the opening and may result in deck web crippling under concentrated loads such as the weight of people or equipment on the deck during construction.

SDI-FDDM provides a method for the design of the small or medium openings in composite steel decks. In this method, the concrete above the top of the deck along the opening’s edges, perpendicular to the ribs, is assumed to act as a shallow beam, as illustrated in Figure 6. This beam can be designed as a reinforced beam or as a structural plain concrete Figure 5. In-plane shear loads on the deck.

Figure 6. Unsupported opening model for small or beam to carry the sum of the dead medium openings. Courtesy of SDI-FDDM. weight of the deck-slab plus the superimposed design loads. The end reaction from this shallow beam must be supported as a point Structural Considerations load on the composite deck-slab adjacent to the opening.

The size of openings in the deck may be categorized as small Note that closely-spaced openings may need to be treated as a openings (up to 12 inches), medium openings (1 foot to 4 feet), medium or large opening. When the group of small or medium and large openings (over 4 feet). Per the SDI Floor Deck Design openings runs perpendicular to the span of the deck, the width of Manual (FDDM), large openings should be designed to have all the hole should be considered to be the overall length along the deck bearing edges supported by structural framing. Openings string unless there is adequate deck remaining between the holes. that are of medium or small size may be accommodated with- However, when the groups of openings run parallel to the bearing out structural frames. It is highly recommended that the deck direction of the deck, the width of the opening can be considered not be removed from the opening before the concrete is cured. as the width of a single hole (Figure 7 ).

Additionally, non-compliance could lead to potential safety issues.

Check with your local regulations and Summary project requirements on whether it is permissible to cut the deck. Cutting Openings and penetrations in composthe deck before the concrete is poured ite slab decks are an unavoidable part and cured reduces the flexural capacity of any structure to accommodate the of the deck and can induce excessive installation of various mechanical, elecdeflection. This can lead to concrete trical, and plumbing systems. Typically, ponding during construction. An assoopenings are created by core-drilling the ciated increase of the dead load on the concrete floor or setting sleeves to create deck may result from additional conan opening before concreting. Due to crete poured to provide a level floor the potential safety issues in cutting the elevation. Also, cutting the web of the deck, check with your local regulations steel deck before the concrete is poured and project requirements before proceedcan reduce the steel deck’s vertical Figure 7. Opening group arrangement. ing. Openings can reduce the structural capacity of the composite deck. To maintain the deck’s structural stability and strength during its service life, a qualified structural engineer should evaluate the openings and their impact on the structural performance of the slab/deck system and provide a reinforcement plan as required.

Per SDI-FDDM, large openings should be designed to have all deck bearing edges supported by structural framing. Small or medium penetrations may be accommodated without structural frames. Note that, for the design of small or medium openings, location and spacing of the openings should also be considered.

A close grouping of penetrations transverse to the span direction of the decking should be treated as a single large opening.■

10 STRUCTURE magazine

Natasha Zamani is the Code and Standards Senior Manager at Hilti North America. (natasha.zamani@hilti.com)

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structural FORENSICS Why Did It Crack?

The Challenge of Determining the Root Cause of Cracking in Thick and Restrained Joints

By Elizabeth Mattfield, P.E.

W

hile many clients seek to pinpoint a singular cause for cracking of welds, it can rarely be attributed

to one single mistake. Most often, a crack is produced in a "perfect storm" of errors made during the design, procurement, and execution phases of fabrication. Individually, these oversights would be unlikely to cause weld failures but, combined, they can cause disastrous results to any welding operation, even in reputable shops.

Longitudinal crack at the weld toe.

A large steel fabrication shop was assembling and welding built-up columns for a new high-rise building in Manhattan. During fabrication of one column, the shop’s quality control staff encountered visible cracking on the base metal of a welded joint. At the time of the discovery, welders were joining elements of 5½-foot-wide columns to be encased in concrete, which contained 3¼-inch-thick plates offset from the column’s web that would serve as connecting elements for the steel framing once encased. These embedded plates were joined to the column via 3-footwide, 3¼-inch-thick stiffeners extending from the web of the column to create a plate surface in the outside face of the future encasement of the column. The 3¼-inch plates were joined at perpendicular angles to each other by welded double bevel tee joints with back-gouging.

To confirm the extent and origin of the crack, magnetic particle testing (MT) of the welded joint and surrounding base metal was conducted by the shop’s quality control inspector. It revealed the crack shown in the photos, with yellow powder accumulating in the cracked metal to distinguish the extent of cracking. It is clear from the powder's location that this fracture had originated in the heat affected zone (HAZ) at the weld's termination and propagated as a transverse crack into the base metal. Ultrasonic testing revealed that the crack extended 1-inch-deep in the 3¼-inch-thick material.

This fabricator had diligently monitored welding parameters in accordance with a prequalified welding procedure specification (WPS).

This WPS for Group II base metal required the use of a gas-shielded, semi-automatic flux cored arc welding (FCAW) process with 70 ksi wire. This is a process often favored by shops for both its productivity from a wire feeder as well as its penetration, attributed to its reverse polarity. The fabricator’s quality manager was able to provide valuable information such as wire diameter, shielding gas, preheat and interpass temperature, and post weld treatment (PWHT) details.

In this case, a preheat temperature of 225°F had been achieved. This is acceptable by AWS standards for Category B base and filler metal combinations in AWS D1.1:2015 Table 3.3. The FCAW wire was classified as H8, with less than 8 mL/100g of diffusible hydrogen. The double-sided tee joint had even been welded by alternating sides, a practice recommended by AWS to control thermal stresses during welding.

This prompted an investigation of the base metal by the fabricator, who assumed that since everything was prequalified and executed with good practice, there must have been some flaw in the base material.

The fabricator had gone so far as to hire laboratories to perform limited chemical analysis of the steel, yielding no reliable results to indicate why the cracking had occurred.

Upon first inspection of mill test certificates of the steel received, it was evident that, while the WPS was perfectly acceptable for the designed ASTM A572 Grade 50 steel, it did not account for the properties of the steel that was actually received and being welded. In fact, the steel far surpassed the minimum yield and tensile strength specified for ASTM A572 Grade 50 steel, with yield values in the 62-63 ksi range and tensile values in the 91-93 ksi range. From a welding perspective, this steel would fall into Group III base metal, becoming undermatched by the 70 ksi filler metal being used to weld it. Undermatching of filler metal is favored where acceptable, such as in this case, where the design only demanded 50 ksi base metal.

However, the extremely high tensile strength also pushed the basefiller metal combination into Category C, a category which requires a minimum preheat of 300 degrees F. After determination of preheat via a hydrogen control method (Annex H of AWS D1.1:2015), it was verified that, indeed, this base metal should have been preheated to a minimum temperature somewhere between 300° and 320°F. One can argue that the fabricator was entirely within its right to use AWS D1.1:2015 Table 3.3 and that the material was indeed certified as a Group II metal. However, whether or not this material can be classified as a different grade by ASTM or AWS is not the point. Instead, the mill test certificate's information should have raised a flag that this material and and its required preheat needed special consideration beyond AWS's general Table 3.3. This is confirmed in the AWS code's commentary, which advocates against the use of Table 3.3 without careful consideration of factors as covered by Annex H used in the analysis. Simply stated, Table 3.3 is an available tool but it is up to the fabricator to determine if it satisfies the conditions required to make sound welds. In this case, elevated preheat beyond Table 3.3 would undoubtedly have been warranted. Annex H of AWS D1.1:2015 is an excellent tool for structural engineers tasked with reviewing mill certification reports since it aids in the determination of preheat using a combination of factors: chemistry, restraint level, and hydrogen control.

Despite its importance, insufficient preheat is rarely the sole cause of cracking. In this particular case, the weld was joining two very thick

12 STRUCTURE magazine

pieces of material, each 3¼-inch-thick. The volume of weld metal alone produces a joint of extremely high restraint, with stresses far exceeding the tensile strength of the steel during welding and cooling that occurred with each pass. The addition of stress relief holes at each end of the joint would provide a path for relief of heating and cooling stresses. Instead, the weld starts and stops abruptly at the ends of the tee joint, a perfect location for crack formation and subsequent propagation into the base metal.

Another noteworthy aspect of this operation was that the WPS did not have any provisions for post weld heat treatment (PWHT). AWS D1.1:2015 does not mandate the use of PWHT, but it does repeatedly emphasize Transverse base metal crack at the end of the weld. Transverse crack at the end of the weld, that joints must be considered on an individual basis propagated from weld into the base metal. and, where needed, PWHT must be prescribed. In the case of steel over 2 inches in thickness, PWHT in the form of a control of at least some of the most common contributing factors can controlled cooling rate would have been quite beneficial in relieving the often be enough to preclude weld cracking. In this case, the contracstresses induced during welding. tor’s determination of appropriate preheat and interpass temperatures Besides the measures previously discussed, other steps can be for thicknesses over 2 inches and providing stress relief holes taken by production crews to improve the execution of this joint in the joint would likely have been sufficient to prevent the and prevent cracking. For example, utilization of H8 consumables welds from cracking.■ places this gas-shielded FCAW process in a low-hydrogen category, which is a good start. However, current, voltage, and gas moisture Photos courtesy of Atlantic Engineering Laboratories (AEL). contamination are variables of low-hydrogen demand projects that Elizabeth Mattfield currently serves on SEAoNY’s Board of Directors. She can be monitored and controlled to avoid increasing the amount of is also the vice chair of the AWS D1 Subcommittee on Reinforcing Steel, diffusible hydrogen in the joint. a member of AWS D1Q Fabrication and Inspection Task Groups, and a In conclusion, finding a singular cause for weld cracking can be a member of the AISC Code of Standard Practice Committee. challenging task, particularly in a shop with proficient welders and (elizabeth.mattfield@gmail.com) established welding procedures that are rarely questioned. Fortunately, ADVERTISEMENT–For Advertiser Information, visit STRUCTUREmag.org

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structural MODELING Steel Connections

Design-Oriented Finite Element Modeling

By Martin Vild, Ph.D., FrantiĹĄek Wald, Ph.D., and LubomĂ­r Ĺ abatka, Ph.D.

S

tructural engineers typically design standard connections that can be solved in several minutes using

Design Guides, spreadsheets, or simple software. The nonstandard connections are the real challenge. The 80/20

Figure 1. ROFEM with a fine mesh of the specimens tested by Huns et al. (Sekal, 2019)

rule applies: 80% of the time is spent on 20% of connections. Non-standard connections are not only more challenging to design but also more costly and prone to errors. Finite element modeling comes to the rescue, allowing the calculation of complicated problems automatically. It has been used mostly for research purposes at universities or very large and costly projects. However, it is now becoming available for even small design firms to use on a daily basis. The desire for architecturally appealing and structurally complex solutions can lead to the use of novel, nonredundant systems with no prior record of proven performance. This makes safe, reliable engineering tools especially critical.

An alternative is the use of finite element modeling, which is useful, especially for non-standard connections. The model is divided into In connection design, the Component Method, where the connection is simple small elements with defined properties by the process of divided into simple discrete components and a basic model is constructed, meshing. The stress and strain in each element are determined by a has become a standard method for those designing with the Eurocode. numerical method. Two model types are recognized: Design rules are provided to determine the strength and stiffness of 1) Research-oriented finite element model (ROFEM) each component. AISC Design Guides for steel connections describe 2) Design-oriented finite element model (DOFEM) methods for particular joints, but the A standard approach for ROFEM is Component Method is more general to perform an experiment and then and is implemented in most software create an advanced numerical model for structural engineers. The components with fine meshing utilizing measured are designed by standardized analytical material properties and initial imperfecmodels, and internal forces are derived tions, often including residual stresses. based on engineering practice. In current The results of ROFEM should fit as European research into steel connections, closely as possible to the experimenthe design properties of components are tal results. By this process, a validated refined or newly developed. The aim is ROFEM is created, which may be used to make the Component Method also for further numerical experiments, in available for conditions such as joints which the design material properties are of composite steel-concrete structures often used. The influence of the main or for, until now, non-standard connecparameters is examined in a sensitivity tors (e.g., hollo-bolts). Research into the study, where these parameters are varied deformation capacity of components is and their effect on the load resistance also being carried out, which is useful, is investigated. The creation of a valiespecially for cyclic loading during an dated ROFEM is very time consuming earthquake. and costly, yet still cheaper and more The design methods are still available feasible than experiments. ROFEM only for the most common connecalso provides further information that tion types. The Component Method is difficult to obtain by experimental model employs significant simplificameasurements. tions, containing only several springs The design-oriented finite element with linear stiffness. The neutral axis is model uses design material properties approximated for some loading cases, (e.g., bilinear material curve with von and the weakness of the method is Mises yield criterion instead of a true revealed for a combination of loading, Figure 2. Geometry of specimen T2 (dimensions in mm); load versus stress-strain material diagram) and standeformation plot, ROFEA, and experimental curves. e.g., by biaxial bending moment. dard safety factors. The DOFEM should

Connection Design and Modeling

14 STRUCTURE magazine

ideally contain a significantly reduced number of finite elements and nodes compared to a ROFEM. The reduction in the number of elements and nodes significantly reduces computational effort. However, it must be proven by a mesh sensitivity study that the results are not affected significantly by this reduction. The DOFEM must be compared to either a validated ROFEM or traditional design methods – this process is called verification.

A special type of DOFEM is a model using the Component-based Finite Element Method (CBFEM). The method is a synthesis of the Component Method and the finite element method.

The plates are modeled by shell elements and the components, e.g., bolts or welds, by nonlinear springs with their properties based on design codes and state-of-the-art research. CBFEM provides code checks of failure modes that are very difficult to capture by finite element analysis alone, such as crushFigure 3. Load versus deformation curves – verification results; mesh around bolt hole – DOFEM (upper) and ing of concrete in compression or weld ROFEM (lower) (Sekal, 2019). fracture. CBFEM removes the restrictions and most simplifications used in the Component Method. The Validation and verification ensure that the finite element analysis of neutral axis and forces in components for any type of load combination the model is correct. The whole process is described in an example of are determined by the finite element method. a block shear of a bolt group. continued on next page

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Figure 4. Bolted stiffened end plate connection: plastic strains on a deformed CBFEM model (deformation scale 3) and reliability graph.

Validation of ROFEM The experiments by Huns et al. performed at the University of Alberta in 2002 are used for validation of a ROFEM created by Sekal in 2019 in ANSYS software (Figure 1, page 14 ). The tested gusset plates are 0.26 inches thick, the bolts have a diameter of ¾ inch, and the bolt holes are match drilled. Therefore, the bolts are directly in bearing.

A true stress-strain material diagram is used. Only the thinnest plate predicted to fail is modeled. The model contains 190,264 hexahedron elements and needs around 26 hours of computational time on a dedicated server. The ROFEM model shows excellent agreement with the test results (Figure 2, page 14). (The model is considered validated, and it can be used for further parametric studies such as the effect of bolt pitch or edge distance on the block shear resistance.

Verification of CBFEM Model A DOFEM using CBFEM is created based on the numerical experiments performed using the ROFEM validated on experiments. The models are compared to each other to prove the validity of CBFEM. This way, the effect of random imperfections of the specimens in experiments is removed. The DOFEM is further compared to several analytical models for block shear resistance of bolted connections.

The models from AISC 360-10, CSA S16-09 (Canada), EN 19931-8:2005 (Eurocode), and prEN 1993-1-8: 2020 (Eurocode-draft) codes are investigated. Furthermore, the results of analytical models

by Driver et al. (2005) and Topkaya et al. (2004) are presented.

The design-oriented CBFEM model uses shell elements with a rather coarse mesh. The finite element model is created in the background of the software and does not require a high level of expertise about the numerical method from the user. The mesh is predefined near bolt holes. Bolts are modeled as nonlinear springs which are connected to the nodes at the edge of the bolt holes by links with nonlinear loaddisplacement behavior. The bilinear material diagram with insignificant strain-hardening is used for plates. The slight slope of the plastic branch improves the convergence of the solver, and the impact on the precision of results is negligible. The limit resistance of a group of bolts in bearing is determined when the plastic strain at the plate reaches 5% 16 STRUCTURE magazine

(EN 1993-1-5: 2005). The bearing and hole tear-out resistances of each bolt are checked by formulas from the appropriate code. The computational time on a personal computer is in seconds.

The comparison is shown in Figure 3, page 15. All design models are conservative compared to this experiment and corresponding ROFEM. The results of the CBFEM model and ROFEM do not match each other perfectly because match drilled bolts were used in the experiments. The shear stiffness of a bolt in the CBFEM model is set to conform to the average behavior of a bolt in standard holes. The resistance of the CBFEM model is smaller due to the neglected strain-hardening of plates and small limit of plastic strain; the guaranteed strain at fracture of structural steel in tension must be at least 15% (Figure 4 ).

On the other hand, the coarse mesh leads to higher load resistances. The resistance of the CBFEM model nearly matches the resistance determined

by AISC 360-10 and prEN 1993-1-8: 2020. It is conservative compared to the model by CSA S16-09 and, at the same time, unsafe compared to EN 1993-1-8: 2005. The current Eurocode analytical model is known to be too conservative and will be modified in the next generation published in the final draft of prEN 1993-1-8: 2020.

Conclusion The design-oriented finite element model using CBFEM is extensively verified, and the studies are published. It is implemented in several commercial software, such as IDEA StatiCa or Hilti Profis.

The results of finite element analysis are first compared to the traditional analytical design procedures in current codes. The aim is to differ from the analytical procedure by 10% at most. If CBFEM provides unconservative results, the model is also verified against ROFEM validated by experiments. Analytical models often contain several simplifications, e.g., rigid base plate assumption or linear interaction of bending moments around two axes perpendicular to each other. Finite element models are, from their underlying principle, much more precise.

Often, the structural engineer is required to make conservative assumptions and educated guesses when designing non-standard joints, which are not described in Design Guides. CBFEM is a tool able to calculate such estimates in minutes, and provide not only design load resistances but also a visual presentation of behavior and a risk of possible failure modes.■ The online version of this article contains references.

Please visit www.STRUCTUREmag.org.

Martin Vild, Brno University of Technology, Faculty of Civil Engineering, Institute of Metal and Timber Structures. (vild.m@fce.vutbr.cz) František Wald, Czech Technical University in Prague, Faculty of Civil Engineering, Department of Steel and Timber Structures. (wald@fsv.cvut.cz) Lubomír Šabatka, IDEAStatiCa, LLC. (lubomir.sabatka@ideastatica.com)

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structural CONNECTIONS Modern Wood Fasteners The Key to Mass Timber Construction Part 1: Self-tapping Screws

By Alex Salenikovich, Eng., Ph.D., David Moses, P.E., Ph.D., and Marcel Hong, EIT

M

any of the advances we have seen in mass timber construction in recent years are due, in large part, to the availability of modern wood fasteners. The two most common types, self-tapping screws (STS) and glued-in rods (GiRods),

will be discussed in this two-part series. Neither of these fastenings is directly addressed by the current U.S. National Design Specification for Wood Construction (NDS®) or the Canadian Standard for Engineering Design in Wood (CSA O86). These articles provide background and relevant design considerations to assist structural engineers in designing with these novel products.

Many large-format structural timber products have become popular Wood screws and lag screws have proven track records. However, in recent years. Further information on mass timber products can be there are some drawbacks. For example, lag screws must be installed found in STRUCTURE’s January 2017 article, Mass Timber: Knowing in pre-drilled holes, typically drilled in two steps for some sizes of screws with different diameter bits for Your Options. The success of these new the threaded and unthreaded parts of mass timber products is partly due to the availability of new, modern wood the shank. Lag screws can be challengfasteners. Traditional bolts, lag screws, ing and slow to install using a wrench, nails, wood screws, timber rivets, split because larger diameter lag screws may rings, and shear plates have been the require high torque. Power drivers for recognized tools by timber engineers lag screws are prone to overdriving, for their reliable record of performance. which can compromise withdrawal For example, Teco (split ring) timber capacity and fixity. Traditional wood connectors were common in largescrews, in comparison, generally do not span heavy timber trusses and bridges require pre-drilling, but are limited in during World War II, offering high size and capacity and can fail in torsion load capacity. Unfortunately, these same during installation. connectors often require high skill and This is where self-tapping screws enter manual labor with specialized tools the scene. High-performance structural for installation. Modern mass timber screws were developed by researchers construction fastenings, on the other and manufacturers in Europe starting hand, are quick and easy to install and in the late 1990s. Now available from uninstall and can be concealed for aesboth European and North American thetics and fire protection. Modern manufacturers, these screws range in fasteners can also provide ductility and diameter from 5⁄32 inch (4 mm) to 9 energy dissipation under earthquake or ⁄16 inch (14 mm) with lengths up to blast loads. Some examples of modern and exceeding 3 feet (1 m). Although fastenings were covered previously in sometimes referred to as “self-drilling,” STRUCTURE’s August 2014 article, Self-tapping Screws is a more commonly Modern Timber Connections – since then, used term. long self-tapping screws have begun to A key feature of self-tapping screws is Figure 1. Fully threaded screws used as reinforcement. Courtesy dominate the mass timber world. the material: special carbon steel with of MTC Solutions. tensile strength up to 145 ksi (1000 MPa), significantly higher than the steel used for lag screws and Traditional vs. Modern Threaded Fasteners wood screws. Another key feature is the screw geometry. Through Wood screws and lag screws have been around for a long time and are extensive design and test programs, manufacturers have developed often what comes to mind for threaded fasteners. The design criteria features such as thread shapes (for strength and ease of installation), for wood screws and lag screws are clearly defined in the NDS and the extent of threading (partially or fully threaded), head shape (for CSA O86, and fastener sizes and shapes are detailed in ANSI/ASME different applications), and drilling/tapping tips. standards. Material properties for traditional wood screws are not Many of the features, developed for ease and speed of installation, specified; however, most lag screws, as specified in ASME B18.2.1, also have the added benefits of reducing wood splitting and eliminatmust conform to ASTM A307, Grade A for low carbon steel. ing the need for drilling pilot holes in many cases. The high strength 18 STRUCTURE magazine

Figure 2. Force-deflection relationships of axially and laterally loaded screws. Courtesy of Schmid Schrauben Hainfeld GmbH.

steel also makes it possible to drive long screws under high torque without breaking the screw in torsion during installation. Many different head shapes are available for different connection configurations, such as wood-to-wood and steel-to-wood applications. Some heads have built-in washers to dramatically increase head-pull-through resistance, which is an essential property for partially threaded screws, as described below.

Performance

(i.e., tension). The withdrawal capacity of traditional fasteners is limited by the withdrawal resistance of wood and the tensile resistance of the fastener shank. Since the quality and the strength of traditional screws are usually unknown to the designer, the penetration length of the threaded portion greater than 10 times the diameter of the screw is not considered in the design to minimize the risk of tensile failure of the screw. This uncertainty is accounted for in Allowable Stress Design (ASD) using conservative reference values (1⁄5 and 1⁄6 of the mean values for lag screws and wood screws, respectively) and low resistance factors in Load and Resistance Factor Design (LRFD) and Limit State Design (LSD) (0.65 and 0.6 in the NDS and CSA O86, respectively). This significantly limits the effectiveness of traditional fasteners in modern mass timber structures.

Self-tapping screws, on the other hand, provide the unique benefit of withdrawal resistance approximately three times higher than their shear resistance, as shown in Figure 2. It is better to take advantage of the screw’s withdrawal capacity rather than its shear

Although wood screws, lag screws, and self-tapping screws are all used to resist shear loads and/or withdrawal loads, self-tapping screws also possess the ability to transfer load in tension or compression from one end of the screw to the other when fully threaded. Fully threaded screws made from higher-strength steel change the type of failure mechanism generally associated with screws. As a result, fully threaded self-tapping screws can be used for new applications like reinforcement, as shown in Figure 1.

Fully threaded screws transfer load from one part of a wood member into another by the threads of the screw, making it possible to prevent wood splitting, perpendicular-to-grain crushing, and shear along the grain.

Splitting and shear are brittle failure modes that often control the capacity of connections in wood. When splitting or shear failure is prevented, the overall connection capacity is increased until another failure mode is reached, but at a much higher load level. Figure 1 Figure 3. The capacity of inclined screws vs. perpendicular-to-the-face screws. Courtesy of illustrates a variety of cases, including notches and bolt MTC Solutions. groups, both of which have high stress concentrations in shear and perpendicular-to-grain tension, respectively.

Openings in large glued-laminated beams for ductwork or pipes can be reinforced using self-tapping screws.

Another benefit of the fully threaded screws, in addition to high withdrawal capacity, is the elimination of head-pull-through failures because the thread transfers the load, not the bearing around the head. Other examples shown in Figure 1 are shear reinforcement of deep beams, radial tension reinforcement of arches and tapered glulam beams, and compression (bearing) reinforcement at supports.

Resistance Wood screws and lag screws are typically installed perpendicular to the face of wood members to transfer shear forces. Screws can also be loaded in withdrawal

Figure 4. Example of rigging for lifting timber elements. Courtesy of Rothoblaas.

AUGUST 2020

19

(lateral) capacity. The connection can 2) Fastener selection. Self-tapping still transfer the shear force, but an screws have many features such inclined screw, as shown in Figure 3, as thread and shank diameter, full page 25, develops a much higher capacor partial threads, type of head ity. The angle of inclination, 30° to 60° and tip, material and coating, and to the grain in the loaded wood member, more. The designer must choose results in a combination of axial and the right screw for the application shear forces in the screw. As shown in and consider the overall cost to Figure 3, under shear loading, a single the project as well as availability.

Contractor requests for substituself-tapping screw installed at 45° to tions also require careful review. the grain can be equivalent to multiple 3) Design values. Conversion of screws installed conventionally, perpenEuropean design values is required dicular to the face. to determine ASD or LRFD design Another interesting behavior of axially values (and LSD in Canada) to be loaded self-tapping screws is that the concompatible with building codes nection stiffness is nearly ten times higher accounting for load-duration and than the stiffness under lateral loading, as Figure 5. Timber-concrete composite floors made using other adjustment factors. Group shown in Figure 2. This stiffness advanRothoblaas CTC timber fasteners. Courtesy of Rothoblaas. effects must also be considered. tage does come at a cost: brittle failure Ask the supplier for guidance. can occur if screws are overloaded in pure 4) Spacing. Determine spacing requirements parallel- and withdrawal, without visible warning, unlike ductile behavior. However, perpendicular-to-grain, including end and edge distances, by inclining self-tapping screws, as shown in Figure 3, the designer screw lengths for thickness of the members, angle of inclinacan take advantage of the overstrength in axial resistance of the screw tion, and wood density. Tight spacing may induce brittle and may also benefit from plastic deformation through bending. failure modes, such as splitting, row shear, block shear, or Applications group tear out.

5) Pre-drilling. Although self-tapping screws can be installed Fully threaded self-tapping screws are mostly used to connect mass without pre-drilling, screws of larger diameters (3⁄8 inch or timber panels in floor-to-floor, wall-to-wall, and floor-to-wall joints with and without steel hardware. A variety of connection configura10 mm and greater) may require pilot holes, especially in tions are shown in the recent edition of the CLT Handbook (free denser wood species and those prone to splitting (Douglasdownload at clt.fpinnovations.ca). Likewise, these screws can be used fir, Hem-fir, and Western Red cedar). The manufacturer in glulam header-to-beam connections and for local reinforcement of should provide the diameter and length of pilot holes. members, as noted above. They can also be used for attaching lifting Pilot holes are recommended for installing long screws in anchors for CLT panels, as shown in Figure 4, page 25, for loads in compact joints and for reinforcement applications to ensure the range of 2.9 kips (13 kN). accurate installation.

Partially threaded self-tapping screws also can be used in a wide 6) Insertion torsion. Suppliers limit installation torque to stay variety of applications with and without steel hardware to resist below the torsional capacity of the screws. Long, fully shear between two adjacent members. These screws can also be used threaded screws should be inserted without interruptions. to develop composite action between mass timber beams or panels 7) Corrosion. Self-tapping screws used in exterior applications and concrete, as shown in Figure 5. Other applications for partially should be stainless steel or have appropriate treatment such as threaded self-tapping screws include attaching insulation to mass electro- or hot-dip galvanization. timber members.

Design Guides and Current Standards The NDS and CSA O86 do not currently address the design of connections with self-tapping screws. While codes and standards tend to lag behind product development and market demand, specific product approvals can be used in lieu of explicit code recognition. In Europe, designers rely on suppliers for their National Technical Assessment (NTA) and European Technical Assessment (ETA) reports for each screw and connector model – dozens have been tested and approved.

Several of these screws are available in the North American market and some with production, service centers, and design guides for the U.S. and Canada. A few have ICC-ES or CCMC (Canadian equivalent to ICC-ES) approvals. It is best to ask screw manufacturers or suppliers for technical support and copies of their design guides. Pay attention to the following technical considerations: 1) Quality control. The supplier must ensure proper manufacturing quality control (material quality) since connection capacity is highly reliant on the tensile strength of the screw.

20 STRUCTURE magazine

The Future of Self-Tapping Screws Trends to follow include self-tapping screws used for punching shear reinforcement in mass timber panels and new specialty connectors that combine prefabricated steel components with the screws. In life-cycle assessment analysis, screws can be backed off and allow for disassembly of structures for future re-use.

Self-tapping screws have a significant foothold in mass timber construction and will likely find their way into U.S. and Canadian building codes and standards soon.■ Alex Salenikovich is a Professor of Timber Engineering at Laval University in Quebec. (alexander.salenikovich@sbf.ulaval.ca) David Moses (dmoses@mosesstructures.com) and Marcel Hong (mhong@mosesstructures.com) are Structural Engineers at Moses Structural Engineers Inc.

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From the Top Down

Creative Use of Structural Steel in a Concrete Structure

By Chris Crilly, P.E., Douglas Schweizer, P.E., S.E., Wayne Stocks, P.E., and Mark Tamaro, P.E.

Courtesy of Sammy Todd Dyess.

T

he Conrad Washington, DC, the capstone building for the CityCenterDC development, presented several unusual challenges to the design and construction team. The combination of a tight complicated site, the need for large column-free ballrooms, and a below-grade loading dock under the hotel tower compelled the team to selectively use structural steel in a predominantly concrete structure to solve design challenges.

Atrium Skylight The hotel massing forms a trapezoidal shape for a podium structure up to Level 3. There the floor plate transitions to a pentagon shape around a central atrium with two adjacent 8-story wings featuring post-tensioned flat slab construction at the hotel rooms. The pentagon and wings form a layout reminiscent of an awareness ribbon (Figure 1). The full-height atrium is topped by a skylight and concrete slab, supported by a two-way steel beam system spanning 75 feet by 85 feet (Figure 2). W36 beams spaced at approximately 10 feet in each direction were moment-connected to each other to complete the multi-directional beam system. A portion of the concrete floor slab below was hung from the skylight steel to create an extended slab edge over the atrium at the highest occupied floor. The steel dual-beam system provided minimal structural depth over the long-span atrium.

Figure 1. CCDC Hotel structure.

Transfer Girders To fit the full building program on the available footprint and within the design architect’s intent, the design team was required to transfer all but five of the 77 hotel tower columns and many of the concrete shear walls at the third level. To maximize ceiling height within the junior and grand ballrooms, and amenity levels below, the transfer girders were limited in depth to 6 feet. To meet these ceiling height requirements, a steel-framed transfer floor was required with steel plate girders consisting of 4-inch-thick by 4-foot-wide flanges, spanning 55 feet over the grand ballroom and supporting up to four columns. With some plate girder sections weighing over 1,300 pounds/foot, many of the transfer girders required splices with complete joint penetration (CJP) welded and heavy-bolted beam moment connections due to transportation and tower crane limitations (Figure 3).

At steel framing near the tower elevators, the depth of the plate girders was sufficient to accommodate the hotel elevator pits. The pit floors were suspended from the bottom flanges of the plate girders. Vertical reinforcement for concrete columns and walls above were welded to the transfer beam top flange to transfer loads to the podium slab efficiently.

Due to the dramatic differences in column arrangements above and below the podium, many framing conditions required cantilevered transfer beams or other unique framing configurations. The unique and deep framing required careful coordination between the 22 STRUCTURE magazine

Figure 2. Construction progress and completed atrium and skylight.

Figure 3. Transfer girder splice.

Figure 4. Column jacking details.

architects’ finished ceiling and MEP systems, resulting in many web irregularities required portions of the lateral system to be designed penetrations through steel members. Perimeter podium columns were considering seismic overstrength, controlling detailing and certain tightly spaced and located as close to the perimeter as possible to avoid aspects of the lateral design such as collector and chord reinforcement special framing and detailing of the store-front façade. within the diaphragms.

The settlement and tilt of the superstructure due to transfer girder deflection had to be controlled during construction. A custom “boot” Entrance made of 6½-inch-thick steel plates in a horseshoe shape was designed as the base of multiple columns just above the third-floor framing A porte-cochere at the hotel entrance is supported by a slab on metal (Figure 4). The center of the boot created room for two hydraulic deck, steel framing, and a 23.5-foot-deep, floor-to-floor truss spanning jacks while the sides allowed for steel shims to lock the column in 120 feet located at a reentrant corner of the building (Figure 5). Steel place. The settlement at each column was monitored as the above framing at the truss top chord supports up to four feet of soil and post-tensioned (PT) concrete floors were constructed. As determined landscape plantings on an outdoor terrace above. The truss diagonal by slab analysis of the PT slabs, a displacement threshold of 1⁄8 inch members (heavy W14 shapes) were wrapped with gypsum board to of vertical displacement was used to determine when jacking was provide the required fire-rating and were architecturally expressed as a necessary. Hydraulic jacks were inserted into the boot, and the entire design feature in the pre-function space of the hotel’s ballrooms. The tower concrete frame was then jacked back to a level condition. The anticipated deflections for the long span truss required careful coordina1 ⁄8-inch vertical displacement limit resulted in about every third floor tion with the contractor, particularly concerning curtain wall detailing requiring column jacking, closely aligning with the structural analysis and construction sequencing. Pre-loading and sequencing of construcpredictions. Once the concrete tower was fully constructed, steel plate tion options were investigated to determine that expected movements shims were inserted and welded inside the steel boot assembly; the of the truss would remain within the curtain wall design parameters. jacks were removed, and the void grouted solid to transfer the final design live load to the supporting transfer beam. The column jacking Foundations permitted the use of more economical shallow transfer beams as the majority of the dead load deflection could be jacked back to level. The building structure is founded on approximately 1,060 eighteenThis allowed the slab to be designed for a maximum of L/600 live inch-diameter auger cast piles. Several pile caps provide support of load column vertical settlement where “L” was the shortest distance between adjacent columns.

Special attention was necessary to coordinate detailing requirements at the interface of steel and concrete, especially at embed plates, bearing plates, and transfer beams, as the different materials had different fabrication and erection tolerances. In most cases, traditional cast-in-place embed plates and beam end connections were not adequate to transfer the high shear loads. Many of the steel beams were detailed to bear directly on a grout pad and embed bearing plate at the top of the concrete columns. For beams with significant end rotation, elastomeric pads were provided below the beam bottom flange to permit member rotation and avoid excessive moment transfer to the supporting column.

The lateral system used to resist the wind and seismic loads consisted of ordinary reinforced concrete shear walls. Due to multiple transfers and offsets in the lateral system, the transfer of large forces through the podium level diaphragm required local slab thickening and diaphragm reinforcement. Despite the low seismicity (seismic design category B), the horizon- Figure 5. Truss spanning over porte-cochere and supporting the green roof above within tal out-of-plane offset irregularities and nonparallel system the completed prefunction space. Courtesy of Sammy Todd Dyess.

AUGUST 2020

23

NOW

multiple columns in groups of as many as 66 piles. Many of the pile caps required mass concrete operations and temperature monitoring to control temperature during placement and curing, and to minimize the risk of delayed ettringite formation due to the caps being up to 7 feet thick. Foundations along the property line were designed to accommodate future construction of an adjoining building basement below the lowest level of the building. The lowest level of the garage is 40 feet below the water table. To maintain a dry garage, waterproofing was provided on the outside of the foundation walls, and an underslab drainage system with continuous pumping was installed. A new loading dock and tunnel at the second story below grade connect the hotel to the adjacent CityCenterDC complex. Columns above the loading dock and tunnel were supported on 4-foot-wide by 10-foot

10-inch-deep concrete transfer beams spanning 74 feet to allow for truck access to the loading dock. The concrete transfer beams required the use of mechanically spliced 75 ksi rebar utilizing multiple layers of top and bottom steel.

The below-grade levels are two-way conventionally reinforced concrete slabs with beams at specific locations for parking, loading docks, and mechanical spaces. Access to the parking levels is made through a corkscrew ramp at the northeast corner of the site. The ramp interrupts floor diaphragms that provide lateral support for the basement walls. Special analysis was required at the ramp and adjoining slabs to ensure lateral loads from the basement walls were resolved at the interrupted diaphragms. The section of the slab between the corkscrew ramp and the foundation wall was reinforced as a horizontal wall beam to span the entire ramp width laterally.

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The creative use of structural steel (1,368 tons) in a predominantly concrete structure was critical to meeting program requirements and the architect’s design intent and essential in delivering the project on time. Careful detailing at the steel and concrete interface was required to accommodate different construction tolerances and large force transfers. Additionally, due to the complex massing transition, many types of advanced analysis were necessary to provide an optimal building structure.■ All authors are with Thornton Tomasetti in the Washington, DC office.

Chris Crilly is a Vice President and was the project manager for the Conrad Washington, DC. (ccrilly@thorntontomasetti.com) Douglas Schweizer is a Project Engineer and was the project engineer for the Conrad Washington, DC. (dschweizer@thorntontomasetti.com)

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Conclusion

Wayne Stocks is the President of Thornton Tomasetti and provided technical and project management support for the Conrad Washington, DC. (wstocks@thorntontomasetti.com) Mark Tamaro is a Managing Principal and was the structural engineer of record for the Conrad Washington, DC. (mtamaro@thorntontomasetti.com)

Project Team Owner: Hines and Qatari Diar Structural Engineer: Thornton Tomasetti, Inc. and A+F Engineers Architect: Herzog & De Meuron and HKS General Contractor: Turner Construction Company Steel Fabricator: SteelFab, Inc.

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CONTAINERS

R

Fortress Obetz near Columbus, Ohio, is a three-story community gathering space built using 122 shipping containers. It currently stands as the largest container-based building in the United States.

These Military Operations in Urban Terrain (MOUT) training structures were made for Cannon Air Force Base in New Mexico using over 700 shipping containers stacked up to four stories tall.

26 STRUCTURE magazine

By Stephen Shang

epurposed shipping containers have taken root within the construction industry. What were once utilitarian boxes full of cargo out at sea are now seen across the United States and around the world as offices, living spaces, retail spaces, and multi-unit structures. The use of these steel cargo boxes as building materials continues to grow rapidly and, to keep up, structural engineers and the construction industry at large must learn to build these container-based structures with safety in mind.

This is the present challenge. A patchwork of regulations for shipping container structures has emerged, producing confusing and potentially conflicting information as local Authorities Having Jurisdiction (AHJs) have sought to develop specific standards. In some cases, the lack of definitive regulations has led industry participants to ignore building codes altogether, creating potentially unsafe structures. Imagine a construction worker getting trapped inside a container office due to poor structural welds. What if a cantilevered container structure were to collapse due to a lack of structural engineering approval? Tragedies like these would put lives in danger and bring permanent damage to the industry.

Fortunately, the International Code Council (ICC) is taking the necessary steps to create a safer future for container-based buildings.

The ICC is dedicated to developing model codes and standards used in the design, build, and compliance process to construct safe, sustainable, affordable, and resilient structures. Most local governments trust the ICC’s suggested codes and adopt the International Building Code (IBC) into law. Working alongside the Modular Building Institute’s Container Task Force, which is comprised of various shipping container manufacturers and structural engineers, the ICC took steps to incorporate shipping container structures into the building code.

To that end, the ICC has published a new ICC Guideline, ICC G5 – 2019, which is intended “to help state and local jurisdictions – as well as owners, architects, builders, and engineers – in their assessment as to how to design, review, and approve such shipping containers as a building element.” All quotes herein are from this Guideline unless otherwise noted.

The ICC Guidelines break the container-based structures industry into four segments: temporary single units (e.g., construction offices), permanent single units (e.g., equipment enclosures), temporary multi-units (e.g., pop-up retail structures), and permanent multi-units (e.g., multi-family buildings). Because these four segments are distinctive, shipping container building codes should not be one-size-fits-all solutions. For example, a single unit ground level office should not be regulated as a multi-story apartment. The

ICC Guidelines make it clear that permanent structures built from containers, “like any other building structure, are required to comply with the codes,” both non-structural and structural. However, for temporary structures, the ICC Guidelines state that they “may not be requiring full compliance with the provisions of the building code.”

Specific to structural code compliance, one of the critical problems is the lack of information on material properties and specifications for the steel elements of the container. The ICC Guidelines solve this problem by providing a section on Referenced Standards and demonstrate how the shipping container industry tests the structural integrity of each container. A Convention for Safe Containers (CSC) Safety Approval Plate, fastened to the exterior of the structure, distinguishes containers that are built, tested, and inspected against the ISO standards, providing the necessary data and information on the construction of the specific container. “A code official can reasonably rely on a data plate to confirm that a container was built and inspected to the appropriate ISO standard.” A container without a CSC Safety Approval Plate can and should be rejected by code officials.

The ICC Guidelines also address the interior of the containers and their wood flooring. What has caused concern for some is rooted in misunderstanding. The ICC Guidelines provide evidence supporting that it is highly unlikely that a contaminated container would make it into the marketplace, and they cite evidence proving that the chemicals used to treat the wood floors are harmful only to insects as a repellent, and not to humans.

The current Acceptance Criteria pertaining to shipping containers, ICC-ES AC462, is not meant for overall building code compliance but instead establishes the physical and chemical properties of the container. This regulation is not retroactive and, although it is the most utilized regulation, it is not the only path forward.

As the ICC Guidelines evolve into more definitive requirements, the ICC will provide a ratified amendment to Chapter 31 of the 2021 IBC. This new building code will incorporate shipping containers for the first time, and provide data for code officials and the industry to ensure these container-based buildings are structurally safe even when modified. Additionally, the code provides a roof exemption and a simplified structural design methodology for single unit containers.

Considering all the previously discussed guidelines, a future of a well-defined shipping container building code is becoming a reality.

The adoption of these guidelines will allow the shipping container construction industry to evolve safely. It will ensure that each container structure is safe and that there is a starting framework to engage in proactive dialog. Now, one can imagine a future where container-based structures help in solving problems instead of creating them, possibly by providing affordable housing in major urban areas or extra space in overcrowded schools. A different picture results from well-regulated shipping container structures, one that comes with an abundance of benefits for the businesses and communities that use them.

To learn more about shipping container building code, read the ICC G5-2019 Guideline for Safe Use of ISO Intermodal Shipping Containers Repurposed as Buildings and Building Components (https://bit.ly/31ZD7o0) and the Modular Building Institute’s Safe Use and Compliance of Modified ISO Shipping Containers For Use as Buildings and Building Components white paper (https://bit.ly/36ikrit).■ Stephen Shang is the CEO and co-founder of Falcon Structures, a leading manufacturer of shipping container-based structures. Additionally, Stephen serves as a member of the Texas Industrialized Building Code Council and the Modular Building Institute’s Board of Directors. (stephen@falconstructures.com)

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27

structural COMPONENTS Round HSS Essentials

By Kim Olson, P.E.

R

ound hollow structural sections (HSS) are used in a plethora of applications – from bridges to transmission

towers and stadium roofs, or from handrails to posts. HSS are also used beyond structures. For example, HSS are used as sprinkler pipes, oil transmission lines, and pistons, which can make sourcing a confusing headache. This article assists in navigating it all from a structural engineer’s point of view.

Figure 1. A53 pipe.

In addition to these differences in intended use between the two steel products, many additional details are critically important for engiRound hollow structural sections are not only aesthetically pleasing neers, especially as they relate directly to matters of cost and quality. and a favorite for architectural design, but they are also efficient Consider yield strength. No matter the grade, A500 material’s yield structural members. With their lack of a weak axis, they are superior strength will be greater than A53 piping. Although A53 was, at one in compression. Their closed shape makes them preferred when tor- time, the standard specification for round shapes, specifying A53 for sionally loaded. When designing connections to round HSS, there columns or braces of a building results in a thicker, larger section than are fewer limit states to consider due to the geometric nature of if using the stronger A500. Structures designed with A500 require the section. Round HSS can also be filled with concrete to increase less steel by weight; the cost-saving implications are clear. compression capacity and provide fire resistance.

An A500 round also has a tighter outside diameter (O.D.) and wall tolerances. When using an A500 round for a building column, you could specify an HSS8.625×0.322 with an outside diameter tolerance Materials of +/-0.75% and a wall tolerance of +/-10%. The A53 equivalent, Currently, Steel Tube Institute (STI) producers dual-certify all of their an 8-inch standard pipe, has an O.D. tolerance of +/-1% and a wall products to ASTM A500 Grade B/C, meaning that the material meets tolerance of -12.5%. Another word to the wise: A53 pipe (Figure 1) the specification requirements for both A500 Grade B and Grade C. is available only in lengths of 21 feet and 42 feet. A500 rounds can In 2017, the American Institute of Steel Construction’s (AISC )15th be produced in lengths from 20 feet to 75 feet.

Edition Steel Construction Manual was released. In it, the capacity When selecting section sizes for structural design, you can be assured tables are calculated for A500 Grade C to reflect this as the predomi- of not only the desired cross-sectional dimensions but also the necnant material in the marketplace. Therefore, Table 1. Commonly available round HSS essary straightness with A500, as producers the design community should design using and corresponding NPS designations. must also adhere to a straightness tolerance Grade C, as that is being purchased and what specified in A500. With A53, there is no speciHSS Designation Standard Pipe has been provided for many years – not only fication in the standard for how straight the HSS3.5X0.216 3" STD PIPE for round sections but for all HSS. pipe must be.

Round sections should be specified as Thus far, this discussion has focused on the HSS3.5x0.300 3" X STRONG PIPE either A500 or A1085. Historically, the structural characteristics of A53 and A500, but HSS4x0.226 3 1⁄2" STD PIPE belief was that A53 was the most available what happens on the outside matters just as HSS4.5x0.237 4" STD PIPE round section and, therefore, the most costmuch. When an A53 pipe is specified, part of efficient. This is not the case. A53 is the its material cost is for the sealant that producers HSS4.5x0.318 4" X STRONG PIPE standard specification for steel, black lacquer use to coat the outside of the pipe. In order to HSS5.563x0.258 5" X STD PIPE coated, welded, and seamless steel pipe. It is weld to these pipes, a fabricator must remove HSS5.563x0.375 5" X STRONG PIPE intended for use in mechanical and pressure the sealant, creating an unnecessary cost and HSS6.625x0.280 6" STD PIPE applications as well as for use in ordinary extra step in the fabrication process. The bare steam, water, and air lines. ASTM A500 is surface of the A500 tube makes it easier to paint HSS6.625x0.432 6" X STRONG PIPE the standard specification for cold-formed, after fabrication is complete. Also, because A53 HSS8.625x0.322 8" STD PIPE welded, and seamless carbon steel structural pipe is produced to carry pressurized steam, HSS8.625x0.500 8" X STRONG PIPE tubing. Available in four grades, A through water, or gas, the manufacturer must hydroHSS10.75x0.365 10" STD PIPE D, it is intended for use in construction and statically test the product, ensuring that it can structural applications. Unlike A53 piping, withstand pressure when in use. If A53 piping HSS10.75x0.500 10" X STRONG PIPE which is only round, A500 is available in is used in structural applications, the product HSS12.75x0.375 12" STD PIPE more shape options, most commonly round, includes the cost of those tests that a structural HSS12.75Xx0.500 12" X STRONG PIPE square, and rectangular. application does not require.

Design

28 STRUCTURE magazine

Lastly, if previously designing handrails with the “1⁄3 stress increase,” using A500 Grade C permits the use of the same sections as when specifying A53 with the stress increase.

ASTM A500 and ASTM A1085 have limitations for sizes with peripheries less than or equal to 88 inches. Anything larger than a 28-inch O.D. round section cannot be speciHandrails fied as A500. However, rounds even that large are not HSS1.9 x0.180 produced to the A500 specification domestically. Currently, Sizes x0.145 the largest A500 sections made in the U.S. are 20-inch Round HSS can be specified in a wide variety of shapes.

O.D. It is worth noting that, by the end of 2021, there will x0.125 Discerning what shapes are readily available is a little trickier. be a new domestic mill producing sections up to 28-inch HSS1.66 x0.140 You may have noticed that there are hundreds of round O.D. In addition to the periphery limits, A500 and A1085 x0.134 HSS sizes listed in the software and in manuals used for also have limits on wall thickness. Currently, the maximum x0.125 design, although not all sizes are produced domestically. thickness of an A500/A1085 member is 0.875 inches. It Engineers frequently wonder why there are fewer options is anticipated that this limit will be increased to 1 inch HSS1.315 x0.133 for A53 pipe than A500 rounds. A53 pipes are designated in time for the opening of the aforementioned new mill. x0.125 to a Nominal Pipe Size (NPS), referring to a “nominal” If a project requires members that exceed what is curoutside diameter (O.D.) in inches plus one of three scheduled wall thick- rently produced in A500 or A1085, there is piping produced for other ness (standard, x-strong, and xx-strong). They are sized this way because industries that can be used in structural applications, with caution.

A53 pipes, designed to carry pressurized steam, air, or water, must work Most commonly, products that meet specifications such as ASTM with standardized fittings and valves. There is no such need with A500 A252, used for pipe pile foundations, or API 5L, for the oil and gas tubes, which are designated with much more precision and, accordingly, industries, can be procured in diameters up to 80 inches. more efficiency. With A500 rounds, the outside diameter and wall thickness, in inches, are carried to three decimal places.

API 5L A good rule of thumb is to specify an HSS member that is equivalent to the NPS sizes. These are listed in Table 1 with the corresponding callout From a structural engineer’s point of view, the following are some of the for an HSS. If deviating from those listed, it is best to check the Steel notable differences between API 5L and ASTM A500/ASTM A1085: Tube Institute’s (STI) Capability Tool (www.steeltubeinstitute.org) • API 5L products come in many grades, denoted by “X65” or to see if the section specified is domestically produced and, therefore, “X70,” which refers to the yield strength (e.g., X65 has a yield commonly available. This can also be done for rectangular sections. strength of 65,300 psi).

• Although API 5L is produced in very large diameters, the Handrails thicknesses of domestically produced pipes are limited to 1 A frequent question deals with the availability of round HSS for inch. Imported material, especially from Asia, is available with handrails. Table 2 lists the sections commonly available in ASTM walls exceeding 1 inch in thickness, although the availability of A500 Grade B/C for handrail construction. such products is often challenging to nail down.

• As API 5L is intended for use as pipelines in the transport of petroleum and natural gas, the tolerances and finishes that are Smaller Sections expected for building products do not apply. API 5L is similar A question often posed when sourcing smaller sections is if ASTM A513 to ASTM A53 in that they are both hydrostatically tested; can be substituted because “A500 is not available.” First, challenge the however, API 5L material is of a much higher quality as it is question of availability. Check the Capability Tool and contact STI for assistance. Second, the answer to the substitution request is, “it depends.” ASTM A513 is a mechanical tubing specification intended for applications where dimensional tolerances are critical, but the strength of the member is not paramount. ASTM A513 has no physical requirements (minimum yield, tensile, or elongation), and A513 material is often not provided with a Material Test Report (MTR) indicating these properties. Therefore, if a substitution is requested, it is essential first to perform coupon testing or review the product’s MTR to ensure that it meets the physical requirements assumed in your design.

As the construction market has grown over the last decade, it seems that the desire for larger pipe and tube sections continues to grow as well. The availability of these sections should be a concern when considering specifying them.

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Larger Sections

Table 2. Commonly available handrail sections.

AUGUST 2020

29

• Today, the most common grade of API 5L pipe available for structural applications is Grade B or X42 (PSL 1); however, there are 40 other grades given in API 5L, many of which may be available.

• In an additional requirement, PSL 2 stipulates a yield-to-tensile-strength ratio of 0.93 maximum for Grade B and X42 up to X80. This is important, as some of the connection strengths given in Chapter K of AISC 360-16 are rooted in the ductility of the material that produces the anticipated connection deformation. The maximum yield-to-tensile ratio for the materials used in the development of AISC 360-16, Chapter K, is 0.80.

• If a large section is required, but the stringent chemical and testing requirements of the API 5L specification are not, it may be prudent to call out the section as “ASTM A500 Grade C or approved equivalent.” This allows a mill that has not gone through the rigorous certifications necessary to obtain an API license to produce the material needed for a construction application, which may save significant project costs.

Figure 2. Complex end profiling.

expected to withstand higher pressures and much higher temperatures than A53 pipe.

• API 5L is not an approved material per AISC 360-16, Specification for Structural Steel Buildings, as specified in Section A3.1a. However, the Commentary to this section states: “Other materials may be suitable for specific applications, but the evaluation of those materials is the responsibility of the engineer specifying them.” It is the EOR’s responsibility to prove the material used conforms to an ASTM Specification specifically listed in AISC 360-16, Section A3.

• API 5L has two product specification levels, PSL 1 and PSL 2.

PSL 1 provides a standard quality level for line pipe. PSL 2 includes additional requirements for chemical composition, fracture toughness, a maximum yield strength, and additional nondestructive testing.

ASTM A252 ASTM A252, Standard Specification for Welded and Seamless Steel Pipe Piles, is a material specification for steel pipe piles for foundations where the steel either acts as the permanent load-carrying member or as the form for cast-in-place concrete piles. STI does not recommend the substitution of ASTM A252 for ASTM A500 unless extreme care is taken. A few items of note follow: • ASTM A252 can be specified in one of three grades. Yield strengths vary from 30 to 45 ksi, and tensile strengths vary from 50 to 66 ksi.

• There are no chemical composition requirements in ASTM A252.

Table 3. Summary of tolerances.

Summary of Tolerances ASTM A500 Grade C

ASTM A252 Grade 3

Intended Use

structural tubing for welded or bolted construction of bridges and buildings and general structural purposes

steel pipe piles for foundations

Minimum Yield Strength

46 ksi

45 ksi

API 5L B

X42

X52

pipeline transportation systems for petroleum and natural gas industries

35.5 ksi

42.1 ksi

52.2 ksi

ASTM A513

ASTM A53

cold rolled, as welded

Grade B

mechanical tubing

mechanical and pressure applications; also acceptable for ordinary uses in steam, water, gas and air lines

no requirement

35 ksi

no requirement

based on cross-sectional area of test piece (same as API 5L)

21

20

based on cross-sectional area of test piece (same as A53)

OD

+/-0.75%

+/-1%

For 2.375" < OD < 24", +/-0.75% (0.125" max) For 24" < OD < 56", +/- 0.5% (0.16" max)

ranges from +/- 1/4 to 1/2%; see ASTM A513

+/-1%

Wall Thickness

+/-10%

-12.5%

For 0.157" < t < 0.984", -12.5% For t > 0.984", max of -12% or -0.1t

ranges from +/- .001 to .009; see ASTM

-12.5%

Weight

no requirement

-5%, +15%

-3.5%

no requirement

+/-10%

Straightness

1/8" per 5' of length

no requirement

max deviation from straight line 2% of pipe length

0.03" per 3' of length

no requirement

% elongation in 2"

Tolerances

30 STRUCTURE magazine

the outside surface. Specifiers should be aware that other specifications for round sections, particularly large pipes, are also produced with a spiral weld (Figure 3). These weld seams wrap around the member rather than straight longitudinally down the member. This is of particular importance if the member is to be used as an element in architecturally exposed structural steel (AESS). In that case, it is likely necessary that the member should be specified on the contract documents that it shall be “straight-seam welded.”

Tolerances Figure 3. Spiral weld pipe.

• Although A252 is frequently produced in large sections, the specification does not speak to the tolerance for sections exceeding 24 inches in diameter and/or 1⁄2-inch thickness.

• The tolerances in A252 are more lenient than A500 for wall thickness, and it has no tolerance for straightness.

• Similar to API 5L, ASTM A252 is not an approved material per AISC 360-16.

If A252 is substituted, the EOR should account for its thinner wall, the lower yield strength, and the variable chemistry that may affect the members’ weldability.

Fabrication

Rounding Up When designing with round HSS, if designers stay in the “wheelhouse” (get it?), with outside diameters ranging from 3.5 inches to 12.75 inches, stick to A500 Grade C. These are the most economical sections because they are the most readily available and demonstrate the most efficient use of the material. If the project demands going outside that range, keep this article handy or contact STI for assistance.■ Kim Olson is an HSS Consulting Engineer with the Steel Tube Institute and is based in Denver, Colorado. (kim@steeltubeinstitute.org)

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When considering the total cost of a structure, the fabrication is a significant portion of the steel package cost. The handling of the material during fabrication is a contributor to the overall fabrication cost; it should be noted that round HSS can be more challenging to handle in the shop as it tends to roll. Marking and adding pieces to quadrants at 90 degrees to each other on a round piece is not quite as easy as it is on a rectangular section. Additionally, when connecting a round section to another round section, like in the truss shown in Figure 2, the cut necessary to connect the branch member to the chord is complex. This fabrication step has been simplified with the implementation of lasers into fabrication shops. However, without lasers, it can be quite complicated. While round sections are often the most efficient per weight, it may be more cost-effective to use a square or rectangular section to aid in the fabrication costs.

All of the materials mentioned in this article have different tolerances innate to their specifications (Table 3). As noted above, it is vital to ensure the assumptions made about the material in the development of the code meet or exceed what is provided in the actual member proposed to be used. Additionally, there are other requirements, like straightness, that may be worth investigating if an alternate material is sourced for a project.

Weldability The requirements for the chemical composition of the commonly specified structural steels and, in particular, the limiting values of carbon equivalents, have been selected to facilitate weldability. The American Welding Society’s AWS D1.1, Structural Welding – Steel, in Table 3.1, lists prequalified steel materials and grades that have been selected because they have historically displayed good weldability.

ASTM A53, A500, A1085, and API 5L Grade B, X42, and X52 are all listed as approved base metals for prequalified welding procedure specifications (WPS). Steel grades not listed in Table 3.1 may be new and have simply not been incorporated into D1.1 or, as is the case for ASTM A252, have been excluded because their mechanical properties and chemical compositions are not sufficiently defined.

For these materials to be used, a special qualification test is required.

Weld Seams ASTM A500 and A1085 round sections are produced with a straight seam weld, with the outside weld bead scarfed or cut smooth with

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31

education ISSUES Used the Most, Taught the Least

An Analysis of Current Wood Engineering Education in U.S. Universities

By John Lawson P.E., S.E., Michelle Kam-Biron, P.E., S.E., and Brent Perkins P.E., S.E.

S

tructural engineers are becoming aware of the impact the selection of structural materials can have on the environment.

The building industry is acknowledging and embracing the contribution of the sustainable potential of wood to reduce the environmental footprint of a project through its carbon-storing capabilities and renewable qualities.

Relevant was the introduction of crosslaminated timber (CLT) into the 2015 International Building Code (IBC) and the creation of the International Code Councilâ&#x20AC;&#x2122;s (ICC) Tall Wood Building Ad Hoc Committee. The Committee investigated the viability of increasing allowable areas and heights of mass timber construction, which resulted in code changes for the 2021 IBC to provide for allowable story heights of mass timber to 9, 12, and 18 stories depending on assembly fire ratings, occupancy, and other safety requirements.

With its use in most residential construction, wood is already a highly common construction material in the U.S. The need to embrace sustainability, will expand wood design and construction into new sectors in the future.

The rise of tall and large-scale mass timber construction will require more engineered and performance-based design approaches than currently practiced. Are students in the U.S. adequately prepared by their higher education institutions and degree programs to meet these new demands?

The Current State of Wood Engineering Education To fully realize the potential of wood used as a structural material in modern buildings, there first needs to be a data-based understanding of the current status of wood engineering education in our existing higher education systems. The National Council of Structural Engineers Associations (NCSEA) surveyed, in 2019, higher education institutions that offer accredited civil engineering and architectural engineering programs on their inclusion of timber design class materials in undergraduate curricula. With two-thirds responding, preliminary observations 32 STRUCTURE magazine

made through this independent survey confirm that, while nearly 100% of the surveyed U.S. universities offer steel and concrete design courses, only 52% offer a wood design course to undergraduates (Figure 1).

Of those universities that do offer a wood Figure 1. Percent of architectural and civil engineering schools that design course, it is offer the indicated course to undergraduate students. often only available biennially or triennially, typically only listed as an elective or cross-listed as a dual graduate/undergraduate course. Past NCSEA structural engineering curriculum surveys also indicate that universities often combine Figure 2. Reasons why timber design is not offered. wood and masonry design into a single course, even though is also listed as a significant factor. In fact, the design methodology and mechanics are among the schools that offer wood design, significantly different for these two materials. a good portion of the programs use partAs a direct result, approximately half of time adjunct teachers to cover that class due civil, structural, and architectural engi- to the lack of full-time faculty with wood neering students graduating from U.S. design experience. The limit on credit hours schools may have either no exposure or is deeply rooted in how a 4-year engineering very limited exposure to the proper appli- program operates. For the program to be cation of wood as a structural material. competitive and viable in 4 years, most of This absence of foundational knowledge the engineering programs limit their total from their education will result in either required semester credit hours to around 120 avoidance or improper and/or ineffective to 135, thus discouraging additional courses. use of wood when these students enter the Also, the accreditation process of the degree structural engineering workforce. program (ABET) only requires the ability to With this evident lack of wood engineering conduct engineering design without expliccoverage in the U.S. higher education cur- itly requiring the inclusion of any particular riculum, potential reasons for this deficiency material. These conditions inevitably result were also surveyed, and the results reveal that in choosing steel or concrete design as the there are many contributors to the lack of required design class, while leaving wood out availability of wood courses (Figure 2). The entirely or just listing it as an elective class. leading reasons include the limit on program The consequences of these gaps in classroom credit hours, lack of school support, and lack instruction result in students with engineerof student demand. Lack of professors who ing degrees lacking the skills to research, are familiar with wood design and research design, and build with wood. It limits

innovation in wood design and reduces the likelihood of wood use in construction and infrastructure development.

But there is also hope that the current mass timber movement will set in motion a renewed interest in innovative wood architecture.

Although the mass timber market itself is still in an early development stage, signature projects in the U.S. and around the world have already started to positively impact people’s perception about building with wood. Student demands have been rising in many schools in the U.S. There is a timely opportunity for the wood industry to partner with educators to develop a strategic focus on wood engineering education in undergraduate civil, structural, and architectural engineering programs in the United States.

Table 1. Core Syllabus Guide.

Wood Education Symposium Recognizing significant changes in modern wood construction due to the development of new modern materials and manufacturing techniques, the ASCE/SEI Wood Education Committee (WEC) is actively working on multiple projects with the ultimate goal of updating wood education in the U.S. to cope with these exciting new developments.

To that end, the WEC organized a full-day wood education symposium at the annual ASCE/SEI April 2017 Structures Congress in Denver, Colorado. Collaborative partnerships were established to assemble key wood construction influencers from academia, engineering, and industry to participate in the symposium. To establish a foundation for this effort that was inclusive of all the stakeholders, for the first time, a partnership was formed between the WEC representing the academic sector, the National Council of Structural Engineers Association (NCSEA) Basic Education Committee (BEC) representing the structural engineering profession, and American Wood Council (AWC) representing the wood industry. Symposium participants placed a strong emphasis on developing a recommended wood design curriculum that can be used at undergraduate and graduate levels. An additional high priority was the development of a strategic plan that would help the industry better understand current gaps and assist in addressing needs for the adoption of wood courses by architectural and civil engineering programs around the country, especially those currently lacking them.

As a result of the symposium, four main issues were identified for current wood education. Participants also developed priorities for actions that can be taken to help resolve these issues.

Key Wood Engineering Education Issues As a result of the symposium, four main issues were identified for current wood education.

Participants also developed priorities for actions that can be taken to help resolve these issues.

• Current Civil Engineering programs consider steel and concrete design as core courses while wood design is treated as either unnecessary or optional, and graduate programs most often are entirely devoid of wood related education.

• There is a lack of faculty with knowledge of wood engineering. While almost every structural engineering department is able to teach steel and concrete, wood is usually taught by part-time or adjunct faculty, often resulting in a lack of rigor and focus on wood engineering fundamentals.

• There is a disproportionally more significant amount of steel and concrete research at major universities as compared to wood, and a majority of Ph.D. students (future faculty) have no exposure to wood-related research.

• There is currently no established mechanism for reciprocity of courses between universities.

The proposed strategy to improve wood engineering education was designed to address these significant issues comprehensively.

Critical components of what is needed to support success are Educational Materials, Curriculum Definition, Widespread Adoption, Comprehensive Materials Science Education, Accessible Information, Education Beyond the Classroom, and Leadership in Advanced Degrees.

The ASCE/SEI WEC, NCSEA-BEC, and AWC continued to work together after the symposium to develop a strategic plan in tandem with implementing two key elements: 1) A crucial part of this expansion involves new and seasoned educators continuing to develop their wood design courses online, with input from other educators and engineering practitioners.

2) ASCE’s Wood Education Committee decided upon the development of a syllabus template based on input from engineering practitioners and academics currently fluent in wood engineering.

A copy of the Wood Education Symposium report may be found at asce.org by searching “wood education.” continued on next page

AUGUST 2020

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content from the best-practices template with each iteration. Alternatively, the core syllabus guideline has been provided with reduced classroom hours to address the situation where wood design contents were combined with another course such as structural analysis, wind and seismic design, or masonry design.

When comparing the core guideline with the best-practices approach, it can be observed that the WEC thought some topics would derive little benefit with additional hours in a best-practices situation, while other topics would benefit from additional time. Moreover, best-practices provide new topics identified by practicing engineers as important.

The best-practices template should be a goal for those striving to offer a course that will devote all credit hours to wood engineering.

The list of hours for both quarter and semester terms provides instructors guidance as to how to pace their course under different school calendar arrangements.

Table 2. Best-Practices Syllabus Guide.

Working to Fill the Void

Syllabus Guideline Templates The Wood Education Committee began its development of syllabus templates by assembling a subcommittee of WEC members, balancing university academic experience with engineering practice experience. This effort intends to provide a standard reference to any educators who are interested in teaching wood in their program. Following a three-step process, two syllabus templates were developed: one of minimum core material for a university course in the engineering design of wood structures and another for a course striving to meet best-practices.

The Committeeâ&#x20AC;&#x2122;s first step was assembling a list of potential topics within a wood engineering course. Secondly, the list of topics was grouped into those necessary for a minimum core program, those recommended for

34 STRUCTURE magazine

the best-practices achievement, those best reserved for a graduate-level course, and other topics best covered in a separate engineering support course.

For undergraduate education, the Committee then focused on topics for minimum-core and best-practices categories.

Based on committee member experiences, the suitable number of hours of classroom instruction was recommended for each of the topics for both semester and quarter systems. The results of that effort are presented in Table 1 ( page 33 ) and Table 2.

In Table 2, topics in italics are unique to the best-practices syllabus guideline.

The intent of the minimum-core template is for professors, who are unfamiliar with wood and looking for a place to start, to utilize it as a baseline for their course. Then, as they gradually prepare and develop their course over several terms, they could add

Meeting the building construction industryâ&#x20AC;&#x2122;s demand for university undergraduates with education in wood engineering requires university programs and faculty to be familiar with wood as a modern construction material. It will likely be a long process considering the current state of higher education on wood design. It will not be easy when many faculty members do not have any wood engineering education, perpetuating the cycle. Hopefully, the syllabus guideline templates and subsequent efforts by ASCE/ SEI WEC and NCSEA BEC will serve as initial steps to help break this cycle by providing easy access to educational information in this exciting field. The Committees continue to work together to create opportunities for wood engineering courses and to develop educational resources for those interested in teaching it so that graduating students will be better prepared for this changing building industry.â&#x2013;

John Lawson is a Professor in Architectural Engineering at Cal Poly, San Luis Obispo, California. (jwlawson@calpoly.edu) Michelle Kam-Biron is the Vice President of Education for the American Wood Council. (mkambiron@awc.org) Brent Perkins is an Engineer with Dudley Williams and Associates. (bperkins@dwase.com)

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Concrete Masonry Association of CA & NV Phone: 916-722-1700 Email: info@cmacn.org Web: www.cmacn.org Product: CMD18 Design Tool for Masonry Description: Structural design of reinforced concrete and clay hollow unit masonry elements for design of masonry elements in accordance with provisions of Ch. 21 of 2010 through 2019 CBC or 2009 through 2018 IBC and 2008 through 2016 Building Code Requirements for Masonry Structures (TMS 402).

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IES, Inc. Phone: 800-707-0816 Email: info@iesweb.com Web: www.iesweb.com Product: VisualAnalysis with Design Description: Once upon a time, there was an engineer overwhelmed with software headaches. As deadlines loomed, he fought against frustration. First the tools were oppressive and clumsy. Then the licensing got ugly. Fortunately, our hero switched to IES and design tasks started feeling more like slaying dragons.

LUSAS Phone: 800-975-8727 Email: Terry.Cakebread@Lusas.com Web: www.lusas.com Product: LUSAS Description: For more than 35 years, LUSAS has helped its clients to analyse, design, and assess all types of infrastructure projects. Our innovative, flexible, and trusted software solution can be applied to diverse applications across a range of industries. Model structure and ground together to consider true interaction.

RISA Phone: 949-951-5815 Email: benf@risa.com Web: risa.com Product: ADAPT-Builder Description: Powerful and easy-to-use 3-D finite element software for multistory reinforced concrete and post-tensioned buildings and structures. Builder delivers comprehensive workflows for complete analysis and design. Combine gravity, lateral and post-tensioning actions for efficient, complete, and accurate design. Integrate with various BIM software for seamless project deliverables.

Product: RISAConnection Description: The cutting edge of next-generation connection design software. Featuring full 3-D visualization, shop-drawing style views, and expandable engineering calculations for all limit states, RISAConnection is an essential tool for engineers who use steel. Its complete integration with RISA-3D and RISAFloor allow one-click connection design for entire structures.

Product: RISAFoundation Description: The ultimate tool for analysis and design of a variety of different foundation types. Featuring an open modeling environment, finite element analysis, and full integration with superstructure analysis programs; you wonâ&#x20AC;&#x2122;t find a better choice for retaining wall, spread footing, combined footing, mat slab, or pile cap design.

Trimble Phone: 678-737-7379 Email: jodi.hendrixson@trimble.com Web: www.tekla.com/us Product: Tekla Tedds Description: Automates repetitive and error prone structural and civil calculations, allowing engineers to perform 2-D frame analysis, access a large range of automated structural and civil calculations to U.S. codes, and speed up daily structural calculations.

Product: Tekla Structural Designer Description: The power to analyze and design multi-material buildings efficiently and cost effectively. Fully automated and packed with unique features for optimized concrete and steel design. Helps engineering businesses win more projects and maximize profits. Quick comparison of alternative design schemes through cost-effective change management and seamless BIM collaboration.

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Trimble Inc. Phone: 800-874-6253 Email: info@geospatial.trimble.com Web: https://monitoring.trimble.com Product: Trimble 4D Control Description: Enables project stakeholders to monitor critical infrastructure including dams, bridges, mines, and buildings surrounding construction sites and tunnels in real-time. Providing unparalleled movement analysis and extensive support for a wide variety of monitoring sensors, multiple sites can be managed from a single, customizable platform.

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All 2020 Resource Guide forms, are now available on our website.

STRUCTUREmag.org.

AUGUST 2020

35

structural FORUM On the PATH to SE Licensure

By Brian Falconer, P.E., S.E., SECB

C

urrently, there is no Structural Engineering (SE) Licensure in New York State. For those of you that are unfamiliar, SE Licensure provides a unique license to distinguish structural engineers from other professional engineers. In general, the intent is to prevent less experienced engineers from designing more critical structures. The arguments for establishing an SE License are readily available on the NCSEA website (https://bit.ly/2AEa3Y2) and the SE Licensure Coalition website (https://bit.ly/2C7Nnjk).

As the chairperson for the SE Licensure Committee for the Structural Engineering Association of New York (SEAoNY), I am often asked, “What is the status of SE Licensure in New York?” Unfortunately, there isn’t a satisfying short answer to that question.

The pursuit of SE Licensure is a campaign as opposed to a short-term goal.

For New York, looking to initiate an SE License is a significant lift for a variety of reasons. First, geography – the closest state to New York to have an SE License is Illinois; therefore, we cannot claim we are falling behind our neighbors. Second, lobbying is expensive and complicated – New York has a large population and a large legislature; therefore, lobbying the continually changing legislature as a whole is an expensive proposition. Third, public knowledge – the general public does not know anything about licensure much less about SE Licensure and why it would be to their benefit; therefore, public education has to be provided. All states have similar obstacles, but probably to varying degrees.

Something else that all states have in common is some form of professional resistance. At first, P.E. holders who do not design critical structures are typically resistant to the idea of SE Licensure. Some object to losing the “right” to design these structures, and others think it is unnecessary regulation that will lead to lots of other licensing. Architects and Owners question if this is going to cost them more. With patience and reason, most of these professionals can be encouraged to see the short and long-term value of having more qualified people doing their critical

36 STRUCTURE magazine

SE Licensure: Title Restrictions, Partial Practice Restrictions, Full Practice Restrictions, and Roster Designations as found on the NCSEA website.

structural work and cease to feel threatened or dismayed by it.

To start a path toward licensure, the Committee went to the NCSEA website Resources for SE Licensure (https://bit.ly/2Z5bB6G) and downloaded a few articles. We continued reviewing the materials there and downloading more articles to organize our committee and our tasks and goals to advance SE Licensure.

We have spent the last few years clarifying what SE Licensure should mean in New York state, educating our membership about it, building relationships with New York engineers, architects, owners, and legislators, and producing articles, letters, and emails for promoting and defending SE Licensure.

At this point, we are preparing marketing materials, legislative language, and organizing to lobby our legislature. Yes, this is a lot of work. Yet, marketing materials are similar from state to state, and the legislative language is related to existing legislative language for engineers and other professionals.

Lobbying your legislature is quite a unique experience unless you hire someone to do it for you. We do not have the money to do that at this point, so this may be the most unnatural and challenging task for us to complete ourselves. I think it is valuable for us to concentrate as a group on some things

that we all have an interest in making more common from state to state.

As simple as the concept may be, SE Licensure will always be a state-controlled process. As mentioned, it must be tailored to the specific conditions of each state. A more consistent national approach would strengthen the case for SE Licensure in all states, much like the national case for adoption of the International Building Code. The broad reasons for having an SE License are not unique to any state. Our most critical structures will perform better and be more efficient if we have more qualified structural engineers responsible for their design. Whether your extreme event is wind, snow, earthquake, or flooding does not really matter.

With this in mind, I would like to consider a few of the characteristics that are selected nationally. Keep in mind that I am not criticizing states for adopting lesser standards. Obviously, New York has no standard when it comes to SE Licensure. However, I am suggesting that these lesser standards should be a stepping-stone to the desired greater good.

Title Act vs. Practice Act A Title Act allows you to have the legal title of Structural Engineer. A Practice Act

restricts the practice of designing some structures to a Structural Engineer. For instance, in a title act state, any Professional Engineer can design a hospital structure; however, in a practice act state, only a Structural Engineer can design a hospital structure. Without any knowledge of exactly who the Professional Engineer of Record and Structural Engineer of Record are, would you feel more comfortable going to a hospital during an earthquake in a title act state or a practice act state? I would feel more comfortable going to the hospital in a practice act state. New York’s goal is to get a Practice Act. The public is better served in every state by having its most critical structures designed by the most qualified Structural Engineers. Everyone’s goal should be to get a practice act.

National Standard for the Threshold Structure Should an essential facility be designed by a Structural Engineer in one state and by a Professional Engineer in another? Certainly not. Essential facilities should be designed by licensed structural engineers in every

state. What about when a dynamic analysis is required? What about when simplified wind and seismic designs are not an option?

What about buildings where more than 500 people gather in one area? What about buildings with an occupancy above 5000?

Many people practice structural engineering on some level, and few structures are going to require an SE License to design them. However, defining those buildings consistently at the national level should be our goal.

Grandfathering Among practicing professional engineers, it is popular to say everyone can be grandfathered if they have a current PE License just by filling out a form. This is not in the public’s best interest in the short term; however, it can be in the long term. At the same time, you do not want to suddenly exclude engineers that have been doing this critical work from doing any more of it.

We need to limit grandfathering into SE Licensure to only a P.E. that is already doing the critical work before the law goes into

effect. That means that someone that wants to be grandfathered should demonstrate experience in doing critical structures to obtain their SE License.

Most states do not have an SE License.

Hopefully, this article develops an interest in pursuing an SE License in many of those states. Some states are already somewhere along the road to licensure, and this can provide renewed energy for your campaign. A few states that already have an SE License Title Act will read this and, hopefully, be encouraged to pick up the mantle to go the rest of the way. I cannot predict how the path unfolds for each of us, but I am confident that we can arrive at the same place together.

If you are interested in the SEAoNY suggested threshold or grandfathering, please visit our website (www.seaony.org/SELicensure).■ Brian Falconer is a Principal in the firm Severud Associates, and he is the Structural Engineering Licensure Committee Chairperson of the Structural Engineers Association of New York. (bfalconer@severud.com)

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AUGUST 2020

37

NCSEA News NCSEA

News from the National Council of Structural Engineers Associations

National Council of Structural Engineers Associations

2020 Structural Engineering Summit: Virtual Event Registration Opens

The Structural Engineering Summit draws the best of the structural engineering field together for the best practical education with expert speakers, a leading trade show, and compelling networking at an event designed to advance the industry.

2020 has been a little different than most years and, because of that, the Summit may look a little different as well. NCSEA is consulting with experts in meeting and event planning as well as a task force developed by the host hotel (the MGM Grand) to assist with the evaluation to host a safe and healthy IN-PERSON Summit.

So, what does that mean to you?

You can register now for the VIRTUAL Summit at an amazing Early-Bird Rate, which entitles you to: • 22 Hours of Education Available (Live and Rebroadcast) • 14 Hours Live-streamed Education • 8 Hours of Live Rebroadcasts with Q&A • Virtual Trade Show Solutions • Easy Virtual Access to Leading Industry Suppliers • Set Appointments, Review Latest Materials, and More

If it is decided that a safe IN-PERSON Summit can be held, your virtual registration will serve as a down payment for your registration to the event in Las Vegas. By registering now, you will receive the early bird price for VIRTUAL and lock in the early bird price for the IN-PERSON event. All registration fees are refundable up until 10/16/2020 and hotel reservations may be cancelled 48 hours prior to arrival date for a full refund. So you can register worry-free to receive the best rate!

This year's Summit will host the keynote panel: What’s Happening with the Future of the AEC Industry. This exciting session will focus on the trends, technologies, and innovations that will shape the structural engineering profession and the entire Architectural, Engineering, and Construction (AEC) industry in the future. It will showcase a leading architect – Vibhuti (Vickie) Harris, HKS, Inc.; a contractor – Greg Gidez, Hensel Phelps; and a structural engineer – Glenn Bell, Simpson Gumpertz & Heger (retired), to discuss what the future looks like from their perspective. They will provide an unparalleled glimpse into the needs of the industry's customers and deliver solutions to address them, as well as what will be driving the AEC industry in the next decade.

Learn more about the 2020 Summit and register before the Early Bird Rate increases (August 21st) by visiting www.ncsea.com.

Consider Having Your Education Offerings Diamond Reviewed!

NCSEA's Diamond Review Program was created to evaluate the quality of continuing education courses, seminars, and conferences geared toward structural engineers. After the education is evaluated and Diamond Review Approved, structural engineer attendees are eligible to receive PDHs in all 50 U.S. states. Diamond Review approval is one of the key values behind NCSEA's high-quality, expert-led webinar program, which has only grown in success since adopting the process. This program can be beneficial for associations and suppliers alike.

• SUPPLIERS to the structural engineering profession so they can provide their structural engineer customers technical education!

• SEAs (and other associations) that have annual conferences, monthly meetings, and webinars to deliver structural engineers a tangible value for their membership in your SEA! To submit education to be Diamond Reviewed, visit www.ncsea.com. When submitting a course, you will need to have a detailed outline of the program content, the presentation materials, the speaker's qualifications, and the number of continuing education credits to be awarded upon completion of the course. Visit www.ncsea.com to learn more about this benefit to you and your members.

Prepare For The PE Structural Exam with NCSEA

NCSEA’s on-demand course provides the most economical PE Structural Exam Preparation Course available. The course includes 30 hours of instruction: 9 Vertical Sessions and 11 Lateral, and will give you preparation tips and problem-solving skills to pass the exam. All lectures are up-to-date on the most current codes with handouts and quizzes available.

PLUS…students have access to a virtual classroom exclusively for course attendees! Ask the instructors directly whenever questions arise.

This NCEES PE Structural Exam Preparation Course allows you to study at your pace but with instant access to the material and instructors.

Several registration options are available; visit www.ncsea.com to register yourself or to learn more about special group pricing!

NCSEA Webinars

Register by visiting www.ncsea.com

August 11, 2020

September 10, 2020

Randy Kissell, P.E.

Gwenyth Searer, P.E., S.E.

The 2020 Aluminum Design Manual

Gravity Loads and Photovoltaic Panels

August 18, 2020

September 22, 2020

Joshua Schultz, Ph.D., P.E.

Seth Thomas, P.E.

Failure Prediction Model for Structural Glass Design

How to Design for Tsunamis: The ASCE 7-16 Tsunami Provisions and Project Examples

Courses award 1.5 hours of Diamond Review-approved continuing education after the completion of a quiz.

A U G U S T 2 02 0

39

SEI Update News of the Structural Engineering Institute of ASCE Check out the NEW SEI Virtual Events Page www.asce.org/structural-engineering/virtual-events

Engage with the profession, connect with your colleagues, and learn new skills.

• NEW Career Path Series: Insights with Glenn Bell and SE Industry Leaders Join for engaging discussions for every level of structural engineer: from where to begin to possibilities beyond principal. Live sessions are free for ASCE/SEI Members, but space is limited. Register today! #SEICareerPaths Session 1: Find a Career Path That Suits You with Judith Mitrani-Reiser, Ph.D., A.M.ASCE, NIST SEI/ASCE Members have free access to the July 21 video online.

Session 2: Starting Out – Entry Level to Project Engineer – Tuesday, August 18, 1 pm US ET Cherylyn Henry, P.E., F.SEI, M.ASCE, and Fernando Martinez, EI, P.E., A.M.ASCE

Career Resources

• ASCE Career by Design – Profession Toolkit, Mentor Match, and more including Six Tips to Ace Your Virtual Job Interview https://collaborate.asce.org/careerbydesign/home • Career Connections https://careers.asce.org/jobs • Civil Engineering Salaries www.asce.org/civil-engineering-salaries

NEW ASCE Virtual Technical Conference 2020

A first-of-its-kind multi-disciplinary technical event powered by ASCE Institutes. Hear from top leaders from offshore wind technology to outer space and everything in between. September 14-18 Register Now! vtech.asce.org #VTech2020 SEI Sessions on: • Conceptual Design of Buildings and Bridges - an Expert Panel Discussion • Millennium Tower Retrofit • Structural Engineers (SE) 2050 Commitment Program

SEI Local Activities

View the May 5 presentation SEI President Glenn Bell gave to the SEI Oregon Chapter on the Joint Vision for the Future of Structural Engineering, Confidential Reporting on Structural Safety CROSS-US, and SE 2050 https://bit.ly/3fiq98S

Congratulations to the 2020 Recipients of the O. H. Ammann Research Fellowship in Structural Engineering Antonio Zaldivar De Alba, S.M.ASCE – University of Illinois at Urbana-Champaign Mohammad Aghababaei, S.M.ASCE – Texas A&M University Laura Liliana Hernandez-Bassal, S.M.ASCE – University of California, Davis Livia Costa Mello, EIT, S.M.ASCE – University of Houston Abhishek Pathak, S.M.ASCE – State University of New York at Buffalo Learn more at www.asce.org/structural-engineering/ammann-research-fellowship

Sponsor/Exhibit to reach industry professionals. Contact Sean Scully at sscully@asce.org. www.structurescongress.org #Structures21

ETS Call for Abstracts – Due September 2.

Sponsor/Exhibit to reach industry professionals. Contact Sean Scully sscully@asce.org. www.etsconference.org #ETSC21

SEI News Read the latest at www.asce.org/SEINews SEI Standards Visit www.asce.org/SEIStandards to view ASCE 7 development cycle Errata 40 STRUCTURE magazine

SEI Standards Supplements and Errata including ASCE 7. See www.asce.org/SEI-Errata.

If you would like to submit errata, contact Jon Esslinger at jesslinger@asce.org.

CASE in Point News of the Coalition of American Structural Engineers Did you know?

CASE has tools and practice guidelines to help deal with a wide variety of business scenarios that structural engineering firms face daily.

Whether your firm needs to establish a new Quality Assurance Program, update its risk management program, or keep track of skills engineers are learning at each level of experience, CASE has the tools you need!

The following documents/templates are recommended to review/use if your firm needs to update its current Quality Assurance Program, or incorporate a new program into the firm culture: 962 962-B 962-C 962-D Tool 1-2 Tool 2-4 Tool 4-2 Tool 4-4 Tool 9-2 Tool 10-2

National Practice Guidelines for the Structural Engineer of Record National Practice Guideline for Specialty Structural Engineers Guidelines for International Building Code Mandated Special Inspections and Tests and Quality Assurance Guideline addressing Coordination and Completeness of Structural Construction Documents Tool 2-1 Risk Evaluation Checklist Developing a Culture of Quality Tool 4-1 Status Report Template Project Risk Management Plan Project Kick-off Meeting Agenda Tool 4-3 Sample Correspondence Letters Tool 4-5 Project Communication Matrix Phone Conversation Log Tool 10-1 Site Visit Cards Quality Assurance Plan Construction Administration Log

NEW CASE Publications Released!

CASE Tool 2-6: Structural Engineer Job Descriptions When targeted to people outside the firm, well-written job descriptions entice qualified people to apply for jobs with your firm. To get the most qualified candidates, list both quantitative and qualitative requirements such as experience, education, and desired personality traits. These types of qualifications help to eliminate undesirable candidates.

When targeted to people inside the firm, job descriptions can be utilized as a powerful management tool. The details contained in a well-written job descriptions form the basis for developing a clear understanding between employee and manager of what is expected of the employee.

Managers can also use the terms in the job description to determine how the employees performed when conducting performance appraisals. The criteria used for performance evaluations ideally would match the expectations listed in the employee’s job description. The job description for the position above the employee’s current position can be used to explain what is required for that person to earn a promotion.

The job descriptions contained within this tool are intended to be used as a template for you to create job descriptions for your firm.

Word files are provided with detailed descriptions along with a matrix with abbreviated descriptions when comparing engineering levels.

You can purchase these and the other Risk Management Tools at www.acec.org/bookstore.

WANTED: Engineers to Lead, Direct, Engage with CASE Committees!

If you are looking for ways to expand and strengthen your business skill set, look no further than serving on one (or more!) CASE Committees.

Join us to sharpen your leadership skills and promote your talent and expertise to help guide CASE programs, services, and publications.

We currently have openings on all CASE Committees: Contracts Committee – responsible for developing and maintaining contracts to assist practicing engineers with risk management.

Guidelines Committee – responsible for developing and maintaining national guidelines of practice for structural engineers.

Programs Committee – responsible for developing program themes for conferences and sessions that enhance and highlight the profession of structural engineering.

Toolkit Committee – responsible for developing and maintaining the tools related to CASE’s Ten Foundations of Risk Management program.

To apply, your firm should: • Be a current member of ACEC • Be a member of the Coalition of American Structural Engineers (CASE); or be willing to join the Coalition • Be able to attend the groups’ regular face-to-face meetings each year: August, February (hotel, travel partially reimbursable) • Be available to engage with the committees via email and video/conference call • Have some specific experience and/or expertise to contribute to the group • Please submit the following information to Heather Talbert, Coalitions Director (htalbert@acec.org): • Letter of interest indicating which committee • Brief bio (no more than a page) Thank you for your interest in contributing to advancing the structural engineering profession!

Follow ACEC Coalitions on Twitter – @ACECCoalitions.

AUGUST 2020

41

business PRACTICES Speed Kills

Transformation of the Practice of Design

By Joseph Tortorella, P.E.

W

hen the author entered the industry 41 years ago, there were no desktop computers. Everything was done by hand calculation, punch cards, and hand drafting.

There were “job checkers,” a person in the architect’s office who continuously checked the project team’s drawings for coordination, completeness, and constructability. Projects followed a set schedule. There was no fax machine or email to send RFI’s through quickly. No drop boxes or project information exchange sites. No Federal Express. There was U.S. mail, messenger services, and mylars.

Blueprint machines were often from a service provided by others and, when they were inhouse, the smell of ammonia (developing solution) permeated the office.

Soon, the PC arrived. Eventually, there were programs to simplify analysis work. The volumes of hand calculations were reduced to data entry and output. Suddenly, a structure could be designed more efficiently (but not necessarily better). Bill Gates, the great American entrepreneur, said it best: “The first rule of any technology used in a business is that automation applied to an efficient operation will magnify the efficiency. The second is that automation applied to an inefficient operation will magnify the inefficiency.”

Current inefficiencies in dealing with technological advances moving rapidly ahead have resulted in overall inefficiencies far beyond what existed 41 years ago.

With this newfound speed enabler, owners discovered a need for “fast-tracking” of projects – completing the foundation design and/or superstructure design long before the architects, mechanical engineer, and all the other trades are close to completing their designs. Before finishes (which impact loading) are even being thought about, engineers are issuing final foundation drawings. The owner said, “we understand the ramifications” (high level of risk of cost increase and change orders as well as errors), but is it worth the risk? This also meant bringing the general contractor on board earlier. What started as a brilliant idea for saving time and money suddenly became a pressure-packed method of design. Job checkers became a thing of the past. The time taken to properly design and coordinate projects became 42 STRUCTURE magazine

greatly compressed. “Construction managers” (CM’s) and “Owners Reps” were created.

Now, schedules were compressed as a result of technology, and a much larger design and construction team due to layers were added to manage the process.

With the arrivals of CAD and then BIM, the CM’s and owner’s reps said: “all of these tools are now available so schedules (and fees)

It is time for a change. The author is not suggesting that we revert to the days of hand calculations and hand drafting, or even the days of the “master builder.” The players should slow down, rethink fast track scheduling, and reinvigorate the process. Speak up to the entire team about the downfalls of aggressive schedules. Why is there fear in asking or dictating to the owner that more time is

Does the speed at which we work, fast-tracking and cutting corners, REALLY save money? Too often, it has been proven that it does not. have to be tighter.” While it seems logical, thinking back, it was a recipe that changed the course of engineering forever and, the author believes, set us back in our management of the process. Speed took precedence over accuracy. Elegance took a back seat to economy. Homelife took a back seat to work.

The result was that the engineer became a tool for the Owners Reps and CM’s to use to their advantage to speed the process. The camaraderie that had long been a staple of the industry was losing steam.

Rather than thanking the entire team, the owner was looking for whom to blame for the delays, costs spirals, and errors and omissions.

It was now “every man for himself ” in an endless battle of costs and delay claims, and who was to blame. This was not the “master builder” at work with the entire team gathering around to learn the process; instead, it was a complete loss of control over the process by the design team. This, in turn, created friction and stress along with reduced fees and what the author believes is the “commoditizing” of services. What was an invigorating process suddenly turned into liability control, especially in the U.S. where the legal system encourages frivolous lawsuits. Project meetings were no longer about finding success; instead, they were about finding fault for failures. Does the speed at which we work, fast-tracking and cutting corners, REALLY save money? Too often, it has been proven that it does not.

needed? The time has come to do things right again and take control of our lives. Could you lose the next project? Perhaps. Is it worth what is done to our staff daily to ignore this and keep doing things “business as usual?” The author thinks not.

Specifically, revise the process by 1) eliminating, or at least rethinking, fast-tracking of projects. Instead, institute a new phase before the schematic called the “partnering phase” – with teaming sessions for all members of the team to set the tone for positive communication. 2) Creating an environment of teamwork with the construction team: meet them directly, learn something about them, and everyone will be less apt to get into shouting matches or throw each other under the bus.

3) At the university level, educating students as to the design process. Frequently, students understand the design concepts but cannot translate that into a series of submissions that meet a schedule. Change that by teaching the concept of “construction administration.”

4) Attempting to make a societal shift. Return some level of decorum to our working lives.

Do you really have to be available 24/7 and spend meetings looking at your smartphone?

In short, the author suggests we take a moment to breathe, and listen to each other and to our hearts and minds.■ Joseph Tortorella is the President of Silman. (jft@silman.com)

AUGUST 2020

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STRUCTURE AUGUST 2020

Bonus Content

(structural brick veneer), the following describes the innovations on two of the six buildings. For these two buildings, a brick veneer on steel stud system (BV/SS) was selected (Figure 1).

Performance-Based-Design The advantages of a performance-based-design include the ability to more precisely define the expected performance, increase the chance of achieving that performance, and allow for cost-reducing innovations that deviate from standard practice and/ or prescriptive code compliance.

The first challenge was to convince the stakeholders to expand the structural engineering involvement to include performance-based-design.

Eventually, all agreed that there were opportunities to customize the BV/SS system to reduce cost and to better meet the owner’s needs. The complexities of the walls helped drive the decision.

Figure 1. Two residential buildings at City Creek Center. Courtesy of ZGF Architects.

By John G. Tawresey, S.E.

The City Creek Center's

Performance Criteria/Expectations

Although BV/SS walls are common, structural engineers typically are not involved in the design except for a limited analysis of the backup wall to determine the expected wall deflection (the codes and standards do not provide consistent criteria for the deflection limit). The applicable building codes for this project were the 2006 International Building Code (IBC), ASCE 7-05, Minimum Design Loads for Buildings and Other Structures, and TMS 402-05, Building Code Requirements and Specification for Masonry Structures. These codes contain limited brick veneer performance requirements, leaving considerable freedom to customize performance criteria.

Early in the process, the Owner, General Contractor, Construction Manager, and consultants were involved in discussions about wall performance. The wind and seismic loads were well defined, but the required performance was not. Since the project is located in a high seismic risk category, the seismic performance was a primary issue.

Seismic loads were divided into three intensity levels; 1) frequent event, 2) 500-year return period, and 3) 2⁄3 maximum considered.

The engineer of record provided seismic displacements for each floor at each seismic level. Building wall elements were differentiated by location and geometry – flat or linear walls at the base and typical floors, corners at the base and typical floors, and parapets. Four levels of performance were defined: operational, immediate occupancy, life safety, and collapse.

1) Operational (No damage) – Hairline cracking of masonry bed joints may exist, with or without a seismic event.

Brick Masonry Façade

T

he City Creek Center's masonry façade is an example of a structural engineering project that used performance-based-design to improve upon conventional, mundane brick façade systems.

Located in Salt Lake City, Utah, the project site encompasses 23 acres of land representing two large city blocks. It contains four residential buildings with 535 units, three office buildings, and 700,000 square feet of retail space. A creek runs through the site, thus the name. The exterior walls of the project are brick, precast concrete, and glass.

Eight architectural firms were involved in the project, but only one structural engineer of record, Magnusson Klemencic and Associates (MKA), Seattle. MKA approached KPFF Structural Engineers early in the project to assist in the design of the brick exterior walls.

As a structural engineer specializing in the design of facades or curtainwalls, including walls constructed of brick masonry, opportunities to design a project of this size rarely occurred during the author’s career.

It has been a challenge to convince owners and architects to design brick walls before bidding and show those designs on a set of drawings, instead of specifying performance and requiring the contractor to design the wall. The City Creek project opened the door to this alternative delivery system.

Because of the complexity of the wall, all parties agreed, after much discussion, to include the wall Element Frequent Event design as part of the project design Flat wall – base Operational documents, allowing for a perforCorners – base Operational mance-based-design (PBD) method Flat wall – typical floor Operational to be used.

Although several different masonry Corners – typical floor Operational wall systems were used on the projParapets Operational ect, including reinforced veneer STRUCTURE magazine

Earthquake 500 Year Return

⁄3 Maximum Considered

2

Operational

Immediate Occupancy

Immediate Occupancy

Life Safety

Operational

Immediate Occupancy

Immediate Occupancy

Life Safety

Life Safety

Collapse

2) Immediate Occupancy (Minor damage, repairable) – Failure of caulked joints and separation of window seals is expected and can be repaired. Cracking of masonry bed joints is expected. Some cracking of brick at corners. Some vertical cracking through brick units is likely but limited. Some separation of face shells from the wall and units from parapets and other appendages.

3) Life Safety (Major damage, repairable) – Severe damage to portions of the wall and minor separation from the building, with no panel falling hazard.

4) Collapse (Major damage, not repairable) – Large portions of the wall have substantial damage and create falling hazards.

The Table presents the resulting performance criteria for designing each type of wall.

The edge of slab tolerances were defined; in-out (plus or minus ½ inch), up-down (plus ½ inch up and 1 inch down). The edge of slab tolerance is tighter than typical construction but was agreed upon as the innovation of the connection evolved. The up-down tolerance included the effects of the building frame creep and shrinkage.

Building floors were 9-inch-thick post-tensioned slabs. Edge forms for post-tensioning typically have round holes for tendons.

Placing an embedded bolt in the slab, protruding through some of the holes to connect the brick ledger, would be easy. The bolt could be bent to engage the bottom of the slab form and a coupler added at the end to attach a bracket for a push-pull rod connection to the top of the floor below studs. This eliminated the need for the top of the stud system to have the questionable double-channel detail. The double channel detail is questionable because performance for both in-plane sliding and accommodating differential vertical movement requires careful installation.

The nominal 9 inches from the edge of Corner Design the slab to the face of brick provided the Meeting the operational and immediate opportunity for a custom ledger support Figure 2. Corner test for warping investigation. occupancy criteria for anticipated damage bracket. Friction bolt connections were at the corners of the building presented a preferred over welding. Vertical slotted design challenge. A typical BV/SS wall would not meet the criteria holes in the backup plate accommodated the vertical tolerance, and at the corner. Differential floor-to-floor displacement would break horizontal slotted holes in the ledger accommodated horizontal tolerthe rigid brick corner. Isolation of brick corners can be accomplished ance. Connections were typically spaced at 4 feet on-center, and the by various strategies: ledger angle was a 3×3×5⁄16 weighing 73 pounds for a 12-foot length 1) Eliminate the brick corner and substitute another element, (Figure 3). such as an aluminum plate.

Reinforced Window Lintels 2) Provide a large expansion joint at the corner.

3) Cantilever the backup system from one floor without attachThe design of window and door lintels provided another opportunity ment to the floor above. for innovation. Typically, bricks above a door or window are supported 4) Build a reinforced veneer or reinforced brick panel that is sup- on mild steel angles designed to a deflection limit of L/600. The angle ported on one floor without attachment to the floor above. is exposed to view and becomes an aesthetics issue. Also, there was 5) Warp the backup and brick system by placing the attachment the complexity of the doors and windows being inset 6 inches from to the upper floor at a defined distance from the corner. the face of the brick.

All options were considered. The decision was to use option 5.

Instead of the conventional steel lintel, a structural brick lintel was Options 1 thru 4 could have been developed by analysis without designed and specified. Figure 4 shows a unique pistol-shaped brick additional technical information. But the information to accomplish Option 5 was not available. Warping the masonry (a panel with 3 corners fixed and the fourth lifted or pushed perpendicular to the masonry surface) is not a common design problem, and no information was available. Consequently, it was decided to test the corner. A mockup panel was constructed and tested to obtain the information (Figure 2). The test demonstrated that the corner criteria could be satisfied.

Brick-to-Building Connection Innovation For a BV/SS design, the edge of slab detail is important, not only to resist the required loads and accommodate expected differential deflections but also to minimize construction cost. There was a need to improve common details, which usually include slab embedded items that are often not properly located, tilted, and/or missing.

Figure 3. Edge of slab connection.

AUGUST 2020 BONUS CONTENT

Figure 4. Reinforced lintel.

that was fabricated and reinforced with a stainless steel (SS) all-thread (much more economical than SS rebar). The lintel was shored for construction; a panelized lintel was not used due to project space restrictions and lifting limitations.

The Value of PBD The above is only a part of the innovation applied to these two buildings. There is more, like the design of the thin stone façade at the base of the building and much more on other parts of the City Creek Center project as a whole, including the reinforced veneer (structural brick veneer) on the retail portion of the project.

STRUCTURE magazine

The City Creek project demonstrates the value of performance-based-design and designing the curtainwall system in coordination with the rest of the design. For the two buildings, a total of 62 full-size curtainwall structural drawings were required. Costs were reduced and performance enhanced. Most important, the inevitable conflicts between parties involved in a complex curtainwall construction project were significantly reduced. The project became a successful team effort.

Curtainwall structural engineering fees, per square foot, are commensurate with structural engineering fees for the primary structure, but the technology and materials can be more challenging. The initial curtainwall design fees may likely be the reason owners do not take advantage of the overall cost savings, which is a lost opportunity.â&#x2013; John G. Tawresey is a retired CFO of KPFF Consulting Engineers in Seattle, WA. He is a past president of The Masonry Society, past editor of the Masonry Society Journal, past president of the Structural Engineers Risk Management Council (SERMC), past president of the Structural Engineering Institute of ASCE, and a current member of the TMS 402/602 Main Committee. He is a member of the National Technical Programs Committee for SEI and an adjunct professor at the University of Washington. (johntaw@aol.com)

INSIGHTS ASTM A913 Quenched and Self-Tempered Structural Shapes

By Shane Vernon, P.E.

A

lthough the ASTM A913 specification has been around for over 20 years, there has recently been a renewed interest in using ASTM A913 Quenched and SelfTempered Structural Steel Shapes. Weight and cost savings are obtained by using the higher strengths of A913 versus conventional A992.

For building structures, the most significant advantage of this specification is for column and truss sections where the designer can realize a 10 to 20% weight saving by using the higher strength available in A913 Grade 65 as compared to the standard 50 ksi yield strength of A992. This increased strength has allowed steel structure design to compete successfully against other materials. Some recent projects which benefited from the use of A913 include the Allegiant Stadium in Las Vegas, Globe Life Field in Arlington, TX, and the Hudson 66 Boulevard project, “The Spiral,” in New York City.

These structural shapes are also applicable to the bridge market. Recently, the A913 specification has been added to the A709 Standard Specification for Structural Steel for Bridges as Grades QST 50, QST 50S, QST 65, and QST 70. To date, Buchanan County in Iowa has completed a single span bridge made with beams produced to the A913 Grade 65/A709 QST 65 specification. Preliminary fatigue tests at Edison Welding Institute in Columbus, OH, of A913 versus A992, indicated higher endurance stress when utilizing A913. More fatigue property research needs to be completed to make this finding conclusive; however, the initial data is promising. Continued use of A913 in bridge applications is an opportunity for further growth in utilizing higher strength structural shapes to lower the weight and cost of the bridge.

ASTM A913 is available in several W-sections, with W14x90 to W14x730 being the most commonly ordered sections in Grade 65, in the author’s experience. Lighter weights are not available in A913 due to the thermal energy requirement of the process. Specifically, the W-section has to have enough thermal mass to temper the section after quenching. On light sections, there is not enough remaining thermal energy to rebound the surface of the section to the 1100-1300F self-tempering temperature after being processed through the quenching equipment. Currently, A913 W-sections are available from more than one producer and are available domestically through most STRUCTURE magazine

fabricators. Designers are encouraged to reach out to their local steel service centers and fabricators to determine what sections are readily available in A913 and rolling schedule/delivery time frames. Current pricing compares favorably to other structural steel grades and, typically, the weight savings more than offset any price differential.

One of the additional benefits of utilizing A913 wide flange sections is that the specifications require mandatory Charpy impact tests at the Shamrock Trading Project w/A913 beams, Overland Park, Kansas. flange locations. This requirement, 40 ft-lbf at 70°F, provides a level of confidence to be welded to other structural grades such to the design engineer of the resistance to brittle as A992 and A572, and Welding Procedure fracture of the beam. Typically, when using Specifications (WPS) exist for welding the other material specifications, Charpy impact dissimilar steel strengths. One of the unique tests at the flange locations are only available requirements of the ASTM A913 specification from the producer for an additional cost. is for the producer to provide the purchaser Additionally, when using A913 wide flange (service center or fabricator) with weldability sections, the Supplementary Specification S30 data from tests on the previous production in ASTM A6 can be utilized to get Charpy (after contract, upon request). This weldability impact testing at the alternate core location data consists of a complete joint penetration when the flange thickness equals or exceeds 1.5 groove weld according to AWS D1.1 and an inches. The design engineer should specify this oblique Y groove test, according to AWS B4.0. requirement in the design documents.

This is done primarily to verify the preheat When contrasting the chemistry require- temperature requirements of the WPS and to ments of A913 to A992, it is apparent that give the fabricator/customer guidance on the the carbon maximum of A913 is roughly development of their own WPS. half of A992. Metallurgical benefits include The potential of higher strengths of A913 is enhanced brittle fracture resistance, increased continually being researched. A Grade 80 verductility, and improved weldability. Looking sion of A913 was recently approved by ASTM specifically at the Carbon Equivalent (C.E.) and is currently available to the market. The maximums, A913 has a comparable C.E. level use of higher strength structural steel that is to A992 with higher tensile properties. produced in the as-rolled condition, versus A913 phosphorus, sulfur, and copper maxi- built-up sections, would allow design engineers mums are also lower than A992, thus providing to take advantage of the increased benefits of a higher quality structural steel section. The steel structures on projects. For more informalower the copper, sulfur, and phosphorus, the tion, reach out to the author or other producers better the steel’s mechanical properties. Some of A913. They offer technical presentations copper is beneficial for corrosion resistance, and lunch-and-learns to interested but too high a level may create a surface defect. firms and professional engineering Phosphorous and sulfur make steel brittle; that organizations.■ is why ASTM specifies a maximum content of these elements. In summary, for equivalent Shane Vernon is a Plant Metallurgist at Nucor chemistry, higher strength steel can be utilized Yamato Steel in Blytheville, Arkansas. Shane with the same degree of weldability. is also an American Welding Society D1I and The weldability of A913 has been thoroughly D1M Committee Member, Certified Welding tested in fabrication practice and has been Inspector/Educator, ASTM A1.02 Committee in the prequalified chapter of the American Member, and AISC Night School Presenter.

Welding Society D1.1 Structural Welding Code (shane.vernon@nucor-yamato.com) for some time. Within D1.1., A913 is qualified AUGUST 2020 BONUS CONTENT

legal PERSPECTIVES Best Practices

Resilient Design and the Evolving Standard of Care

By Brett Stewart, J.D.

D

espite the politicization of the climate change conversation, there is overwhelming scientific evidence that our climate is altering in a way that is placing added stress on communities, infrastructure, and the general health and well-being of society.

Structural engineers need to be mindful of the potential for increased liability exposures due to a less-predictable environment. The AXA XL Design Professional unit expects a growing number of lawsuits against design professionals from clients who claim that their project should have been able to withstand foreseeable extreme weather events. Many of these lawsuits will claim a breach of the professional standard of care.

For structural engineers, this could translate into claims arising out of unanticipated wind and snow loads on buildings as well as damage to bridges caused by intense stream flows.

Engineering consultants should consider code requirements as a starting point for their design criteria and incorporate anticipated climate change impacts into their designs more proactively than in the past. Some engineers may take issue with what amounts to a departure from largely relying on historical data to inform their design decisions. However, they need to consider that the standard of care is ultimately determined by (1) what they agreed to in their contract, and (2) the conclusions of a trier of fact; i.e., a disinterested jury with potentially little or no engineering experience. Merely complying with codes or government-mandated design criteria does not necessarily mean that the standard of care was met. Instead, the standard of care is a concept that evolves and can be influenced by case-specific facts. Sometimes the standard of care dictates design solutions that exceed clearly defined and accepted code provisions – for example, for seismic, wind, and occupancy live loads. Offering those solutions to the client not only leads to more resilient and longer-lasting structures, but it also reflects the prevailing standard of practice.

Many design professionals have expressed concern about how to communicate the need for appropriate proactive design to a client. They wonder, too, what they should do if a client refuses to follow their advice. The author’s firm recommends the following best practices: STRUCTURE magazine

1) Insist on early dialogue with clients regarding program requirements. This can be a challenge with public agencies who issue RFPs with set design criteria.

Firms can respond to RFPs within the design criteria. Still, it is important to recommend, where appropriate, alternative designs for more robust projects that will last longer in light of changing environmental conditions. Sometimes, this conversation can be reinforced by demonstrating lifecycle cost savings that can be realized with a design that anticipates damage caused by extreme weather events. AXA XL has heard from insureds that clients will later say that what they really needed was for the engineer to tell them what they should have done and to prevent them from doing something that was a bad idea. Sometimes, this equates to recommendations that exceed mere code compliance.

2) Understand that clear and effective communication and documentation are critical to establishing a record of what the engineer recommended.

Engineers will need to “connect the dots” and tell clients why something is a good or bad idea and what can happen, in the engineer’s opinion, if they do not follow the engineer’s advice; e.g., an increased risk of loss resulting in higher lifecycle costs, loss of use and business interruption, or even potential harm to the public. If a client refuses to follow an engineer’s advice, there should be a clear paper trail documenting the decision in writing to the client – typically as a written follow-up to a conversation.

3) Ask for a waiver and indemnity. If a client refuses to follow the engineer’s advice, and if that decision does not place the engineer in any ethical peril, the engineer can request that the client waive any claims against them arising out of the client’s decision to proceed against the advice of the engineer, and to defend and indemnify the engineer against any third-party claims arising from that decision. While it is always a good idea to have this language

(sometimes known as a self-executing indemnity) in the contract with the client, it is not always feasible. Many clients will refuse. However, just by asking for the waiver and indemnity, the engineer is establishing a paper trail and creating what amounts to a trial exhibit that would demonstrate to a jury that the engineer felt the refusal to follow their advice was important…and wrong.

4) Decline to complete professional services. If the client’s refusal to follow the engineer’s advice is a really bad idea (e.g., an obvious life-safety hazard), the engineer should consider suspending or terminating design services – admittedly a drastic measure. Having protections written into the contract at the outset are helpful but, again, not always feasible.

If something is a life-safety hazard, the engineer must communicate their objections to the client, both verbally and in writing, clearly documenting what the hazard is and why the engineer must refuse to complete their services.

5) Remember ethical obligations.

Engineers have an ethical obligation to promote public health, safety, and welfare. Be mindful of actions that can undermine this obligation, such as doing whatever it takes to please a client or signing agreements with an elevated standard of care that puts the client’s interest above all else; i.e., a fiduciary duty. Consultants should not be afraid to cite their ethical obligations as a reason for undertaking or refusing to undertake a specific course of action.

6) Consider the competition. Finally, consultants should weigh what other design professionals are doing on similar projects in the area – an important point when conducting a standard of care analysis.■ Brett Stewart is a Risk Manager, Design Professional with AXA XL. (brett.stewart@axaxl.com)

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