STRUCTURE magazine November 2019

STRUCTURE NOVEMBER 2019

NCSEA | CASE | SEI

CFS/Steel

INSIDE: Hudson Commons

38

Steel Stud Bearing Walls Hot-Dip Galvanizing Amherst New Science Center

8 20 30

LeMessurier Calls on Tekla Structural Designer for Complex Projects Interoperability and Time Saving Tools

Tekla Structural Designer was developed specifically to maximize collaboration with other project parties, including technicians, fabricators and architects. Its unique functionality enables engineers to integrate the physical design model seamlessly with Tekla Structures or Autodesk Revit, and to round-trip without compromising vital design data.

“We’re able to import geometry from Revit, design in Tekla Structural Designer and export that information for import back into Revit. If an architect makes geometry updates or changes a slab edge, we’ll send those changes back into Tekla Structural Designer, rerun the analysis and design, and push updated design information back into Revit.”

Tekla Structural Design at Work: The Hub on Causeway

For over 55 years, LeMessurier has provided structural engineering services to architects, owners, contractors, developers and artists. Led by the example of legendary structural engineer and founder William LeMessurier, LeMessurier provides the expertise for some of the world’s most elegant and sophisticated designs while remaining true to the enduring laws of science and engineering.

Known for pushing the envelope of the latest technologies and even inventing new ones, LeMessurier engineers solutions responsive to their clients’ visions and reflective of their experience.

An early adopter of technology to improve their designs and workflow, LeMessurier put its own talent to work in the eighties to develop a software solution that did not exist commercially at the time. Their early application adopted the concept of Building Information Modeling (BIM) long before it emerged decades later.

While LeMessurier’s proprietary tool had evolved over three decades into a powerhouse of capability, the decision to evaluate commercial structural design tools was predicated on the looming effort required to modernize its software to leverage emerging platforms, support normalized data structure integration and keep up with code changes.

After a lengthy and thorough comparison of commercial tools that would “fill the shoes” and stack up to the company’s proprietary tool, LeMessurier chose Tekla Structural Designer for its rich capabilities that addressed all of their workflow needs. According to Derek Barnes, Associate at LeMessurier, ” Tekla Structural Designer offered the most features and the best integration of all the products we tested. They also offered us the ability to work closely with their development group to ensure we were getting the most out of the software.”

One Model for Structural Analysis & Design

From Schematic Design through Construction Documents, Tekla Structural Designer allows LeMessurier engineers to work from one single model for structural analysis and design, improving efficiency, workflow, and ultimately saving time. “Our engineers are working more efficiently because they don’t need to switch between multiple software packages for concrete and steel design. Tekla Structural Designer offers better integration of multiple materials than we have seen in any other product,” said Barnes.

LeMessurier engineers use Tekla Structural Designer to create physical, information-rich models that contain the intelligence they need to automate the design of significant portions of their structures and efficiently manage project changes.

TRANSFORMING THE WAY THE WORLD WORKS

“Tekla Structural Designer has streamlined our design process,” said Craig Blanchet, P.E., Vice President of LeMessurier. “Because some of our engineers are no longer doubling as software developers, it allows us to focus their talents on leveraging the features of the software to our advantage. Had we not chosen to adopt Tekla Structural Designer, we would have needed to bring on new staff to update and maintain our in-house software. So Tekla Structural Designer is not just saving us time on projects, it is also saving us overhead.

Efficient, Accurate Loading and Analysis

Tekla Structural Designer automatically generates an underlying and highly sophisticated analytical model from the physical model, allowing LeMessurier engineers to focus more on design than on analytical model management. Regardless of a model’s size or complexity, Tekla Structural Designer’s analytical engine accurately computes forces and displacements for use in design and the assessment of building performance.

“Tekla Structural Designer offers better integration of multiple materials than we have seen in any other product.”

Positioning a large scale mixed-use development next to an active arena, a below grade parking garage, and an interstate highway, and bridging it over two active subway tunnels makes planning, phasing and engineering paramount. Currently under construction, The Hub on Causeway Project will be the final piece in the puzzle that is the site of the original Boston Garden.

Despite being new to the software, LeMessurier decided to use Tekla Structural Designer for significant portions of the project. “Relying on a new program for such a big project was obviously a risk for us, but with the potential for time savings and other efficiencies, we jumped right in with Tekla Structural Designer. It forced us to get familiar the software very quickly.”

“Tekla Structural Designer allowed us to design the bulk of Phase 1 in a single model,” said Barnes. The project incorporates both concrete flat slabs and composite concrete and steel floor framing. “Tekla Structural Designer has the ability to calculate effective widths based on the physical model which is a big time saver,” said Barnes. “On this project, the integration with Revit, along with the composite steel design features enabled us to work more efficiently. Adding the ability to do concrete design in the same model was a bonus because we had both construction types in the same building.”

“Tekla Structural Designer helped this project run more efficiently, and in the end it was a positive experience,” said Blanchet.

“Tekla Structural Designer gives us multiple analysis sets to pull from, which gives us lots of control. Most programs don’t have the capability to do FE and grillage chase-down. For the design of beam supported concrete slabs, Tekla Structural Designer allows us to separate the slab stiffness from the beam stiffness, so if we choose to we can design the beams without considering the influence of the slab. In the same model we can use a separate analysis set to review the floor system with the beams and slab engaged,” said Barnes.

Barnes also shared similar benefits with concrete column design. “Tekla Structural Designer does grillage take-downs floor-by-floor, finds the reactions and applies them to the next floor. This allows us to view column results both for the 3-dimensional effects of the structure as a whole and from the more traditional floor-by-floor load take-down point of view.

Doing both has always required significant manual intervention, but Tekla Structural Designer puts it all in one place.” “We reduce the possibility for human error because with Tekla Structural Designer less user input is required,” said Barnes. “Tekla Structural Designer automatically computes many of the design parameters, such as column unbraced lengths. The assumptions made by the software are typically correct, but we can easily review and override them when necessary.”

“Tekla Structural Designer provided the best fit for our workflow compared to other commercially available software.”

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Contents

Cover Feature

N OVEM BER 2019

38 HUDSON COMMONS

By Joseph Provenza, AIA, P.E., Jeffrey Smilow, P.E., Yujia Zhai, P.E., and Motaz Elfahal, Ph.D., P.E.

A fundamental question for every developer on sites with existing conditions is to rebuild or reposition. For the acquisition of a drab eight-story commercial building in Manhattan, developers decided that the 1960s-era cast-in-place concrete building would receive seventeen floors of steel construction.

30 WHEN SCIENCE BECOMES TRANSPARENT

34 PERELMAN CENTER FOR POLITICAL SCIENCE AND ECONOMICS

By Adam Blanchard, P.E., and Jeffrey Abramson, AIA

By Allison Lukachik, P.E., S.E., and Amanda Gibney Weko

The glass façade of the Amherst College Commons is a structural

The Ronald O. Perelman Center for Political Science and Economics

silicone glazed curtain wall system comprised of triple-glazed insulating

involved renovation and reuse of a historic 1925-era building with

units. The curtain wall is hung in tension from a steel roof structure

the construction of a new addition. Structural challenges involved a

cantilevered up to forty feet over the Commons below. Supporting the

cantilevering steel feature stair, two steel transfer trusses, and the use

curtain wall is a paired steel plate assembly and steel tee profile.

of concrete flat-plate floor framing.

Columns and Departments 7

Editorial The IRC – Does It Really Matter?

28

Stephanie J. Young, P.E.

8

12

Structural Systems Steel Stud Bearing Walls

42

Structural Sustainability

By Connor Bruns, S.E., Eric J. Twomey, S.E., P.E., Terry McDonnell, S.E., P.E.,

Resilience: A Rallying Cry We Can Amplify

and Matthew Johnson, P.E.

By Kate Stillwell

Building Blocks SpeedCore

46

Structural Quality Structural Masonry General Notes

Structural Rehabilitation Adaptive Reuse of the Apex Hosiery Company Building – Part 1

By Jennifer Traut-Todaro, S.E.

16

InSights Masonry Testing Technician Certification

By Nicholas R. Lang, P.E.

By D. Matthew Stuart, P.E., S.E., P.Eng

50

Professional Issues Upfront and In Need

By Jefferson Asher, S.E., and John Chrysler, P.E.

By Dallas Erwin and Kate Peterson

20

Structural Practices Successful Detailing for Hot-Dip Galvanizing

By Alana Hochstein

24

Northridge – 25 Years Later Nonductile Concrete Frames

By Keith D. Palmer, Ph.D., S.E., P.E.

In Every Issue 4 52 54 56 58

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

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.

N O V E M B E R 2 019

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A Powerful Software Suite for Detailed Analysis & Design of Reinforced Concrete Structures

EDITORIAL The IRC – Does It Really Matter?

By Stephanie J. Young, P.E.

L

et’s face facts. It is unlikely that the majority of practicing structural engineers are familiar with the material contained within the International Residential Code (IRC).

Why would we?

When we provide a design for a new project, our guidance comes from the contents of the International Building Code (IBC) and related references. We must be familiar with this information, be comfortable with the concepts, and understand how to comply with these standards. Structures have become more complex. The Code and the material standards must keep pace with these changes. The result is a collection of books that would rival my childhood encyclopedia set.

A request that structural engineers add the contents of the IRC to our repertoire would probably result in a groan or at least a small chuckle.

Besides, the IRC itself indicates that its purpose is to allow for the construction of one- and two-family dwellings without the need for an engineered design.

IRC Section R301.1 – “…The construction of buildings and structures in accordance with the provisions of this code shall result in a system that provides a complete load path that meets the requirements for the transfer of loads from their point of origin through the load-resisting elements to the foundation.”

It sounds like we are off the hook now, right?

Well, maybe not. Our services could still be required. IRC language exists which allows for the engineered design of a specific element or system, should that portion of the structure fall outside the criteria for an IRC building. However, the remaining portion of the building may continue to be constructed per the IRC prescriptive requirements.

IRC Section R301.1.3 – “…Where a building of otherwise conventional construction contains structural elements exceeding the limits of Section R301 or otherwise not conforming to this code, these elements shall be designed in accordance with accepted engineering practice.”

In this case, the engineer involved will likely provide the specific design based on the principles and practices they find most comfortable – namely those contained in the IBC. There still seems to be no compelling reason to get involved with a residential code, correct?

So then, why should we?

Our primary duty as engineers is to “hold paramount the safety, health, and welfare of the public.” The public is not only a generic group of people, but includes our friends, families, and ourselves. Most people spend nearly half of every 24 hours in their homes. This is more time than is spent in their offices, schools, churches, or shopping centers.

Yet we treat these facilities as somehow more worthy of our attention.

We, as engineers, have knowledge that can make life at home safer.

STRUCTURE magazine

I expect you can tell that this issue is important to me. Our firm offers engineering services to homeowners – something that is becoming more and more rare. It has been an important part of our 35-year history, and we intend to continue doing so. Contractors and homeowners contact us for assistance with everything from investigating a failing foundation wall to the addition of another level on their house. Through our involvement in these projects, we have found it necessary to rely on the IRC to better understand the basis for the original construction.

Residential designs for new construction have also become more creative, pushing the limits of what can easily be addressed in a prescriptive code. Our firm is often asked to help interpret various IRC sections that have been recently added to keep up with new materials and systems.

While we have found that the majority of the information contained in the design tables follow accepted engineering practices and equations, several assumptions and limitations were involved in their development. Code language generally remains unchanged unless someone speaks up. Maybe “the way things have been done for 20 years,” is just not good enough anymore. It is here where the value of structural engineering knowledge comes into play.

What can we do?

I have been the Chair of the NCSEA Code Advisory IRC Working Group for the past two, 3-year code cycles, and I feel our work has been interesting and productive. Our group has been successful in making code changes that corrected discrepancies and improved clarity.

It is not our vision to change the IRC to become an engineering guideline like the IBC. Each of the codes has specific uses and targeted audiences and serve them well. Our goal is to ensure that the IRC is not just a collection of empirical past practices but is based on proven engineering concepts. Codes are generally considered a summary of minimum requirements and, as our engineering knowledge increases and construction practices change, structural engineers should be monitoring these documents to make sure they remain current and relevant.

So, if you should encounter the IRC during your day-to-day activities, do not shy away. Take a bit of time to review and understand its contents. If you find a concerning issue, bring it to the attention of our committee and we will do our best to address it through the code revision process. If you have a bit more time and interest, volunteer to serve on your State or local Code Advisory Group, or join us at the NCSEA level. All participation is welcome and appreciated.

Structural engineers should do their best to elevate the performance of all structures, including those we call home.■ Stephanie J. Young is the President of Mattson Macdonald Young, Inc. in Minneapolis, MN. She is a member of the NCSEA BOD and Chair of NCSEA Code Advisory IRC Working Group.

N O V E M B E R 2 019

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structural SYSTEMS

Steel Stud Bearing Walls Multi-Unit Residential Construction

By Connor Bruns, S.E., Eric J. Twomey, S.E., P.E., Terry McDonnell, S.E., P.E., and Matthew Johnson, P.E.

P

re-fabricated, structural cold-formed metal framing (CFMF) bearing walls are a trending construction system and an economical

alternative to structural steel or reinforced concrete systems for mid-rise construction. CFMF wall systems are particularly desirable for 6- to 12-story multi-family apartments or condominiums, student housing, senior living, and hotels. Vertically-aligned residential demising and partition walls allow the CFMF to stack like timber-framed or concrete masonry unit

Pre-fabricated, structural CFMF wall panels. Courtesy of Bear Construction Co.

(CMU) bearing wall construction. However, CFMF wall buildings are less height restrictive than timber due to steel’s higher strength and not as labor-intensive as CMU because of pre-fabrication. Additionally, CFMF systems integrate wall panels as the structural system in what would typically be non-structural, stick-built partition walls.

The prevalence of CFMF wall panel systems comes with design and construction challenges. Delegated design integration, trade coordination in a traditionally non-structural element, and fire-resistive detailing are among the challenges for this system. This article summarizes the CFMF system layout process, design and specification options, and considerations that may be overlooked in initial planning and pricing.

System Overview CFMF systems are most efficient when the wall panels align, or “stack,” from foundation to roof. Multi-unit residential construction often integrates programming space for retail, office, amenities, or parking typically at the lowest levels of the building. In these cases, the CFMF bearing walls are constructed on a podium level, typically of structural steel or cast-in-place reinforced concrete. Both systems can be engineered to support discontinuous bearing walls and to provide heightened fire rating separation that may be required between differing occupancies. From the onset of a project, there should be a dialog between the design team and the owner to stack the walls, and ideally the wall openings, to minimize transfers within the CFMF system.

CFMF bearing walls can be spaced between 10 and 32 feet apart depending on the span capabilities of the floor construction. To span between the bearing walls, floor system options include cast-in-place concrete on unshored composite steel deck, cast-in-place concrete on shored long-span steel deck, or precast, prestressed hollow-core planks. Alternatively, floor construction may consist of concrete panels or steel deck supported on CFMF floor joists that span between the bearing walls.

Each floor system has advantages and disadvantages. For example, concrete on unshored composite steel deck requires less labor associated with shoring than shored long-span steel deck; however, unshored steel deck is typically limited to a span length of about 15 feet, where long span deck can achieve up to 32 feet between structural walls.

Precast, prestressed hollow-core planks can achieve similar spans to long-span steel deck; however, planks may require a structural topping 8 STRUCTURE magazine

for floor levelness and are a heavier system resulting in increased load on the wall panels, podium, and foundations.

Compared to steel deck options, CFMF floor joists may be appealing because of their span capabilities without the use of shoring; however, a CFMF floor joist system is generally 6 to 12 inches deeper than a steel deck system leaving less room for MEP distribution, requiring lower ceilings or necessitating taller floor-to-floor heights. Additionally, CFMF floor joist systems may require a fire-rated ceiling assembly where steel deck systems can typically achieve an unprotected firerating within the concrete. Steel deck options (shored or unshored) are appealing, given their simplicity in detailing and thin profile. For both decking and CFMF joist systems, if the span is parallel to a central corridor, a header is required to span from the end of the CFMF wall panel over the corridor. The header is a part of the structural load path and may require a 1- or 2-hour fire rating.

The lateral load resisting system (LLRS) for a CFMF building can be of a variety of structural systems. It may be beneficial to utilize the CFMF walls as the lateral system, relying on either sheeting or CFMF steel straps. In this case, the transfer of overturning moments in the wall systems and transfer of the loads from the CFMF walls to the podium structure are important considerations; in the case of the former, the additional details may detract from the efficiency of the system. Alternatively, walls around the stairs and elevators are an opportune location to introduce reinforced concrete shear walls, CMU shear walls, or steel braced frames for the LLRS. Regardless of the system chosen, the sequence of trades is a critical discussion to have with prospective contractors, whether they are involved early in the project in a design-assist role or bidding the project.

Design and Specification Traditionally, CFMF wall panel construction has been governed by systems that were developed by fabricators and their Specialty Structural Engineer (SSE). The SSE designs these systems, which are tuned to the preferred fabrication and installation techniques of the contractor. An

alternate approach is for the Structural Engineer of Record (SER) on the design team to design a custom stud framing system or to delegate the design of a custom system to the contractor. The SER designing the system is the least common approach and is not discussed here.

An appropriate delegated design, whether for a custom or proprietary system, requires the design team to identify the location and extent of the load-bearing CFMF walls on the drawings. The delegated design of a building system describes a scenario where the SER provides a set of design criteria for a contractor’s SSE to follow to design, fabricate, and install the identified building system. In addition to identifying the CFMF wall location and extent, it is essential that the design team indicate other trades, both structural and non-structural, that interface or are integral to the CFMF walls.

A crucial part of delegated design criteria is the communication of wall and floor loading information to the contractor’s SSE. Floor load plans should be employed to show the magnitude and extent of superimposed dead and live loads, particularly large or non-uniform loads and exterior wall loads. Specific details may also be required to indicate the location and magnitude of exterior wall loads or point loads, such as transfers, corridor transfer beams, and rooftop equipment.

Exterior wall cladding is frequently a partial or complete delegated design.

The intersection of multiple delegated design components can result in poor coordination during construction. The design team needs to clearly document basis-of-design details for the integration of the various systems as a basis for contractor bidding. In addition, a responsibility matrix is a useful tool to document the roles of the Architect of Record (AoR), SER, the General Contractor (GC), the specialty subcontractors, the CFMF fabricator/installer and their SSE, and the exterior wall fabricator/installer and their SSE during the submittal review process and the subsequent

Unshored composite steel deck construction.

construction. The matrix can be published with the construction documents to define the design demarcation for each structural engineer. The design team can rely on the matrix during submittal reviews to indicate necessary coordination with other trades.

Regardless of the system – proprietary or custom – the SER should develop a preliminary analysis of the typical CFMF wall components both to establish the acceptability for the intended layout and to provide a basis of design for pre-construction budgeting and bidding.

This effort validates the approach, establishes design loads for the podium and foundations, helps the SER identify key layout options or constrictions, and indicates to the SER where special detailing, minimum size, or material gauge are required. This will help the SER develop a more reliable delegated design. continued on next page

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N O V E M B E R 2 019

9

Top Track Details Top tracks within a CFMF bearing wall function as a load-distribution element where the floor system (e.g., the low flute of steel deck or the flange of a CFMF joist) does not necessarily align with a vertical stud. Wall panels are typically installed on top of each floor level, so the top track should be designed/detailed to transfer the load of the floor system and upper-level floors to the adjacent vertical stud. In the authors’ experience, it is a false economy for the contractor to take a cost savings by presuming the installers will align the floor system with individual studs.

Construction Sequencing Shored long-span steel deck construction.

Design and Construction Considerations Podium Construction Podium level construction should be designed to heightened deflection criteria to account for the sensitivity of the gypsum wallboard (GWB) clad CFMF bearing walls. Accumulated displacement can result in non-structural finish cracking if a podium level is not sufficiently stiff. Early programming should consider the increased depth of the structure below the first floor of CFMF bearing walls.

Fire Ratings As the primary structural load carrying members, CFMF may be required to achieve up to a 2-hour fire rating. A 2-hour rating is achieved with a second layer of GWB on each side of the wall. This is an additional weight that needs to be considered in the design of the studs and clearly indicated in the delegation language to the SSE. An additional consideration for architects and contractors is the continuity of the rating – it must continue around door jambs, electrical boxes, and similar items integral with the structural CFMF wall. To the extent possible, the design team should coordinate all penetrations into a CFMF wall to occur within a non-structural portion of a CFMF structural wall to simplify the fire rating details during construction.

Future Flexibility While CFMF allows a typically non-structural partition wall to serve as a primary structural element, it does not typically allow for future flexibility. While this may be acceptable for hotels and dormitories, it may be less desirable in apartments and particularly condominiums where owners may want the opportunity to modify their unit or combine units in the future. A hedge against limiting future flexibility is to use a long-span floor system wherein either the exterior and corridor walls are the primary bearing walls, or only unit party walls are the primary bearing walls, or a combination thereof.

Non-Stacked Walls CFMF bearing walls are an efficient system for repetitive usage programs such as residential. However, when atypical programs migrate into, under, or above CFMF bearing walls, inefficiencies encumber the system. This typically takes the form of hot-rolled structural steel within the steel stud walls, an independent structural steel frame, or similar programs. This results in inefficiencies in the CFMF wall design and fabrication and increases the complexity of construction trade sequencing.

10 STRUCTURE magazine

Forethought into the coordination of trades during the vertical erection sequence will drive construction efficiency. Traditional trades such as masons, carpenters, ironworkers, concrete suppliers, and concrete placement workers will need to be staged as each floor is constructed, and they will need to be educated about the integration of their systems with CFMF construction.

Structural Studs vs. Partition Studs Historically, CFMF is not part of the primary structural building frame, typically serving as an exterior backup wall or a partition wall.

While this is part of the intrigue and efficiency of the system, it can create confusion on the construction site. Clearly documenting the structural CFMF in both the structural and architectural drawings is important. It is more important, however, to educate the contractor and their subcontractor, early and often, that the structural CFMF cannot be modified without review and analysis by the SSE for the CFMF. Common field modifications include penetrations through studs for plumbing and electrical systems and temporary removal of studs for construction egress.

Exterior Cladding and Slab Edges The exterior edge of a CFMF bearing wall building can frequently be only the thin edge of a concrete slab on a steel deck. This creates a structural efficiency but can create heartache in the façade depending on the material and attachment system. Determining the façade materials and attachment systems early when considering a CFMF structural system is critical – the special details required of certain façade systems can quickly erode any efficiencies in the structural CFMF. The AoR and SER should establish the basis of design details for the façade attachments and the requirements of both the structural and non-structural CFMF at façade attachments.

Summary CFMF bearing wall buildings are increasingly a cost-effective option in the low and mid-rise multi-unit residential market. As a new approach to design and construction, there is a learning curve for both designers and contractors. Understanding the opportunities and the challenges of the system is key to a successful project.■ All authors are with Simpson Gumpertz & Heger.

Connor Bruns is a Consulting Engineer. (cjbruns@sgh.com) Eric Twomey is a Senior Consulting Engineer. (ejtwomey@sgh.com) Terry McDonnell is a Principal. (trmcdonnell@sgh.com) Matthew Johnson is a Principal. (mhjohnson@sgh.com)

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Lateral System Innovation for Today's Construction Challenges

By Jennifer Traut-Todaro, S.E., LEED AP

T

he millennial mindset is saving our profession. A common question from young engineers – “Why do we do things the way we do them?” – can be just as off-putting to us as it is to the Baby Boomer down the hall. The more experienced engineers often side with GenXer points of view and the played-out stories of rotary phones, record players, and the lost art of hand-drafting. Figure 1. SpeedCore panel module in fabrication. Courtesy of Magnusson Klemencic Associates.

All we want to say is: “because we do.”

The thing is, the next generation is not challenging us. Instead, they Composite systems have been used for years, since pumpable conare challenging the history of how we do things – and it is a good crete was developed and became a structural material. Using the thing they are because many of us have stopped asking, “WHY?” compressive strength and stiffness of concrete to enhance the strength That question becomes more difficult to ignore when, for instance, a and ductility of steel is ideal, but prefabricated steel-plate composite concrete contractor inevitably misplaces an embed to support a steel beam. (SC) wall panel development had gone the proprietary route and lost The Request For Information in the designer’s inbox forces them to spend steam. The nuclear industry saw the safety and speed of the system’s the time they do not have and money the owner did not plan to spend. construction and began to employ it in safety-related blast walls for The Millennial mindset is saving our profession because when we nuclear facilities. They appreciated the additional robustness of the get tired of asking why, millennials will jump in and do the asking for system’s properties, including radiation shielding and resistance to us and, in turn, save the profession. Their answers to those questions extreme loading. The concept was able to gain popularity as an opencan revolutionize everything we do. source option, designed by any engineer and built by any fabricator.

Innovate Ron Klemencic, Chairman and CEO of Magnusson Klemencic Associates (MKA), embraces that questioning mindset. At the 2019 NCSEA Summit keynote, Klemencic stood on the stage and encouraged the industry to ask “Why?” because he constantly asks the question himself – with revolutionary results.

Together with his MKA colleagues and AEC partners, he has brought a previously existing idea forward in new packaging to the benefit of the project team, the owner, and, ultimately, the industry.

The Coupled Composite Plate Shear Wall – Concrete Filled (CCPSW-CF) system is now known as “SpeedCore.”

MKA had been exploring the idea of a composite sandwich panel shear wall system for a taller building application for several years before making a particularly innovative proposal to Rainier Square Tower developer Wright Runstad & Company: build the first tall building project to use a composite core. Rainier Square Tower is a 58-story, mixeduse, high-rise, currently under construction in the heart of downtown Seattle, Washington.

Figure 2. SpeedCore construction detail.

12 STRUCTURE magazine

SpeedCore Coupled Composite Plate Shear Wall – Concrete Filled (CCPSW-CF), or SpeedCore, is a non-proprietary, revolutionary method of composite structural-steel framing. The system consists of two steel plates that are held in position by cross-ties and a concrete core.

During construction, the steel faceplates with the steel cross-ties provide stability under construction loading before the concrete infill is placed. In the case of Rainier Square Tower, permanent internal stability trusses were added for ease of transportation and erection (Figure 1). No additional concrete wall formwork is built on-site. The pre-fabricated, panelized module serves as a permanent formwork for the concrete.

Ongoing research has shown that welded shear stud connectors, in combination with fewer, more widely spaced cross-ties are effective in generating composite action as well (Figure 2). After the concrete infill has cured, it acts compositely with the SpeedCore components of plates, cross-ties, and shear connectors. The steel acts as both wall reinforcement and the primary resistance to tension and shear demands on the

lateral system. No additional wall reinforcehave shut down the Rainier Square Tower projment is placed on-site, greatly expediting wall ect without an innovative solution. Once the construction. The concrete infill, working team behind Rainier Square Tower realized that compositely with the steel faceplates, provides there would be an eight-week demobilization overall flexural and shear stiffness to the structo complete only one level, and came to grips ture because the confined concrete can resist with all the financial and logistical burdens larger overturning compressive loads under related to that extended demobilization, they lateral demands. took a serious look at SpeedCore.

In the SpeedCore erection schedule, there is no need to advance the core ahead of the Rainier Square Tower surrounding steel frame to achieve simultaneous topping out, as in traditional cast-in-place Though MKA had been exploring the concrete core construction. The construction SpeedCore concept for several years, no projschedule is no longer subject to the time and ect team was ready to consider the progressive on-site labor costs of placing formwork and SpeedCore module isometric. building idea and put pen to paper. A team rebar. The module plates and cross-ties are preneeded to silence that internal, nagging “why?” fabricated off-site, leaving the steel erectors to do what they do best: to open their minds to an unconventional option. Once SpeedCore build a kit of prefabricated parts. Embed site placement is a thing of was on the table for discussion, Rainier Square Tower’s general conthe past, as they now arrive already affixed to the modules. The core tractor, Lease Crutcher Lewis, found the system promised substantial is designed for advancing four stories above the surrounding structure savings. No rebar, no formwork, no curing lag, and no demobilizain compliance with OSHA erection standards. tion for outrigger placement all meant a significant reduction to the At first blush, SpeedCore undoubtedly builds faster. When building overall construction schedule. with a concrete core, common practice means that concrete, with its To lend a sense of scale, the outriggers that provide additional days-long curing period, sets the pace. The building schedule is at the lateral stiffness to the structure require 5,200-kip-capacity, buckmercy of advancing the concrete core. “Why?” The formed core must ling-restrained brace web members. This is one of the highest be high enough that, once steel erection has begun, the erector does capacities of BRB elements manufactured. The outrigger loads not have to demobilize and then remobilize. The concrete pour demo- are very high. For the original design, which used a conventional bilization, due to high-capacity dissimilar material connections, would concrete core, MKA devised an embedded truss connection to

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transfer the load from the concrete core to the outriggers. In the SpeedCore version, the concrete is wrapped with the steel that is typically cast inside the wall, allowing for more direct steel-tosteel connections. Concrete’s weakness in tension no longer rules the high-capacity connections, and the eight-week construction shutdown is a thing of the past.

Among the laundry list of challenges faced when designing and building, a significant reduction in a schedule is something to which we should be paying attention. The original cast-in-place concrete core schedule estimated topping out 21 months after steel arrival on-site.

During the planning phase, Lease Crutcher Lewis was confident that the erection of the SpeedCore version of that same building would take only 12 months. Switching to SpeedCore shaved nine months off the construction estimate – almost 43% of the erection schedule offsetting any additional construction costs associated with the system.

The general contractor and the erector bettered their promise by an additional two months, topping out the first week of August 2019.

Long story short, Rainier Square Tower is the real-time market test of the SpeedCore System.

Research Ongoing research is providing a better understanding of the SpeedCore system behavior under lateral loading and how the system’s materials can be optimized. As an early innovator, MKA was not able to take advantage of efficiencies they had theorized that are now being confirmed by research; the designers placed higher importance on a streamlined review schedule and compliance with currently published codes to design and permit the building. For the Rainier Square Tower project, therefore, MKA designed the system conservatively, using the same wall thickness used in the cast-in-place concrete core option and a Seismic Response Modification Coefficient of R = 6.5.

MKA’s design method is documented and available for reference in a joint Pankow Foundation-MKA design guide, Design Procedure for Dual-Plate Composite Shear Walls. This is the most current published design method and is conservative for today’s SpeedCore designs.

The Federal Emergency Management Agency’s FEMA P695 Study preliminary findings assert that SpeedCore achieves R = 8, Ωr = 2.5,

14 STRUCTURE magazine

and Cd = 5.5 – a system efficiency not available during the design phase of Rainier Square Tower. This confers a significant reduction in loads applied in analysis, taking better advantage of the ductility and overstrength of the SpeedCore system. Researchers expect that more testing will facilitate additional optimization, such as increased spacing between ties, a reduction in overall wall thickness, and a reduction in fire protection requirements. Any of these improvements would make the system even more attractive.

There are currently four ongoing SpeedCore research projects. As more research is completed, designers will be better able to evaluate the system’s composite behavior and optimize the system even further.

Klemencic, Dr. Amit Varma (Purdue University – Bowman Laboratory), and the American Institute of Steel Construction (AISC) are collaboratively producing a Design Guide to aid engineers in this optimized design.

Combining “Why?” With Good Practice There is much promise in this system and engineers from all generations must step out of their comfort zone to use it. The project team of Rainier Square Tower took the time and resources to get it right for the benefit of the industry. Early and effective team communication was key in setting up Rainier Square Tower for success. Early mock-ups to evaluate concrete mixes and pouring sequences ensured adequate consolidation and strength. Open-mindedness and realistic goals drove the execution of mock-ups intended to evaluate planned efficiencies for shop and field fabrication methods.

Once the tenants move into Rainier Square Tower and the next innovative building takes center stage, this building will be remembered for pushing the envelope. History will have been made. Asking the question “Why?” might be tiring for those forced to find answers, but it is what makes us better as designers – it is how we ultimately build better. This is the pinnacle challenge of engineering. It is why engineers studied problem-solving in school. It is why they have so much fun in their careers. We should embrace the Millennial mindset and innovate.

For more information about SpeedCore and its use in Rainier Square Tower, visit www.aisc.org/speedcore or contact the Steel Solutions Center at solutions@aisc.org.■ The online version of this article contains references.

Please visit www.STRUCTUREmag.org.

Jennifer Traut-Todaro is a Senior Advisor in the AISC Steel Solutions Center.

Since SpeedCore broke onto the scene, Jennifer has been following the development of SpeedCore research and the progression of the Rainier Square Tower project. (trauttodaro@aisc.org)

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structural QUALITY Structural Masonry General Notes Specifying an Effective Quality Assurance Program

By Jefferson Asher, S.E., and John Chrysler, P.E., FTMS

T

he quest for quality construction following a professional design by the Structural Engineer is not a new concept. The

initial publishing of the 1927 Uniform Building Code (UBC), subtitled the material disciplines “Quality and Design,” acknowledged the relationship between the design and implementation of a construction project. Over the past 90 years, Quality Assurance, the development of a program, and Quality Control, the implementation of that program, have evolved in such a manner that details can often cloud the ultimate intent.

The development of General Notes by Structural Engineers for specific projects can be a challenging task, particularly regarding issues of Quality Assurance and Quality Control. Conflicts can easily develop between the General Notes, the project Specifications, and the governing Building Code requirements. The development of Quality Assurance and Quality Control provisions contained in the 2016 version of TMS (The Masonry Society) 402/602, Building Code Requirements and Specification for Masonry Structures, can help minimize these potential conflicts and provide design professionals with very helpful tools to increase effective communication with all members of a project team.

History Although the concept of Quality and Design was introduced in 1927, it was not until the 1943 edition of the UBC that a mechanism was established to implement quality in masonry construction. Section 204 (b)2 stated that masonry must be continuously inspected by a “Registered Inspector” when the stresses exceeded 50 percent of the design stresses allowed by the masonry design chapter. Even though the code required a “thoroughly qualified” registered inspector, there was no direction on what constituted the qualifications or what to inspect.

The next code cycle (1946) required that the registered inspector be qualified by the building official but, other than being qualified, the registered inspector was given little direction on masonry inspection for the next 30 years. Some progress was made in 1976 when the UBC listed when to inspect masonry, such as during placement of masonry units and reinforcement, before and during grouting operations, and preparation of test specimens. Still, the code provided little guidance on the quality control aspects of masonry inspection.

As the code transitioned into the International Building Code (IBC) in 2000, inspection tables were introduced in the IBC and the referenced material standard, Building Code Requirements for Masonry Structures (TMS 402/ACI 530/ASCE 5). Although similar, these inspection tables contained inconsistencies, with the IBC taking a senior position for inspection tasks. Even with the inconsistencies, this was a significant step forward in formulating consistent Quality Control requirements.

16 STRUCTURE magazine

For several years, both sets of inspection tables matured. In 2009, the IBC contained a detailed list for two levels of masonry verification and inspection tasks in Tables 1704.3 and 1704.4. These tables formed the basis for developing a Quality Assurance program by listing the minimum Quality Control provisions required for masonry construction. The two sets of tables ultimately disappeared in the 2012 IBC since they were redundant with the Verification and Inspection Tables contained in TMS 402-11/ACI 530-11/ASCE 5-11, Building Code Requirements for Masonry Structures.

Structural Notes Since the code has historically been lacking specific Quality Assurance and Quality Control provisions, Structural Engineers have been appropriately listing material and construction requirements on structural drawings in the form of General Notes (as supplemented by the project Specifications). For the most part, Masonry General Notes have been a repetitive listing of material standards, such as ASTM C90 for Concrete Masonry Units, ASTM C270 for mortar, and ASTM C476 for grout. In addition to listing the ASTM Standards, some of the material properties contained in the Standards were also listed, such as the strength of the Concrete Masonry Unit, the strength and mix proportion of masonry mortar (which conflicts with the Standard), and the strength of grout.

Table 1. Minimum quality assurance level.

Designed in accordance with

Risk Category I, II, or III

Risk Category IV

• Allowable Stress Design • Strength Design • Prestressed Design • Strength Design of AAC

Level 2

Level 3

• Veneer • Glass Unit Masonry • Partition Walls

Level 1

Level 2

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For example, there can easily be a con- Table 2. Verification. flict in the way mortar is listed. That is, an Required for Quality Assurance(a) MINIMUM VERIFICATION inconsistent requirement for a specified Level 1 Level 2 Level 3 mortar strength and a given proportion Prior to construction, verification of compliance of mix. Numerous citations in the mortar R R R submittals.

Standards explain why field-tested mortar is not expected to meet the laboratory mortar Prior to construction, verification off ' and/or AAC, NR R R strength as listed in ASTM C270. The priexcept where specifically exempted by the Code. mary reason is that the water-cement ratio of During construction, verification of Slump flow mortar in the wall is significantly lower after and Visual Stability Index (VSI) when selfNR R R the masonry unit is laid when compared to consolidating grout is delivered to the project site. the water-cement ratio in the test specimen.

During construction, verification of f'm and f 'AAC Another significant factor is that the aspect NR NR R for every 5,000 sq. ft. (465 sq. m). ratio of the mortar joint in a masonry wall provides a geometric configuration that is During construction, verification of proportions considerably stronger than mortar in a test of materials as delivered to the project site for NR NR R specimen. premixed or preblended mortar, prestressing grout, It is a customary practice for the Structural and grout other than self-consolidating grout.

Engineer to develop a master-set of General (a) R=Required, NR=Not Required Notes which are intended to be utilized on every project. Of course, each construction TMS 402 Requirements project is unique, and the specific circumstances and conditions which are associated with each project must be considered in the application IBC Section 1705.4 references TMS 402 for Quality Assurance of the master-set of General Notes from project-to-project. Sometimes requirements. There are three levels of Quality Assurance in TMS this does not occur, and General Notes which may be applicable to 402. Determination of the minimum quality assurance level is based one project are left intact where different requirements may apply. on both the chosen design methodology and the Risk Category which Further complicating this situation is the ever-changing nature of applies to the project at hand. material standards and code requirements. This is all particularly true The Risk Category is as-defined in IBC Table 1604.5 and, to deterwith respect to quality assurance and quality control issues. There is, mine the appropriate Quality Assurance level, the Risk Category is however, a simple approach to circumvent the potential confusion. split into two groups. One group (Risk Categories I, II and III) covers most buildings, and the other (Risk Category IV) encompasses critical facilities expected to be operational after a disaster.

TMS 402/602 Requirements TMS 402 contains a simple table for determining the minimum The Building Code Requirements and Specification for Masonry Structures Quality Assurance level applicable for a given project. A modified document contains two standards, along with their commentaries: version of the table is shown in Table 1.

1) Building Code Requirements for Masonry Structures designated The most typical situation will include a structural design approach as TMS 402 (formerly designated as TMS 402/ACI 530/ which utilizes either Allowable Stress Design or Strength Design, ASCE 5); 2) Specification for Masonry Structures designated as TMS 602 (formerly designated as TMS 602/ACI 530.1/ASCE 6).

These standards are produced by The Masonry Society’s Committee TMS 402/602. The Code covers design and construction of masonry structures, while the Specification is concerned with minimum requirements for masonry construction. The Code contains provisions dealing with Quality Assurance in masonry construction (along with many other topics); the Specification covers subjects such as Quality Assurance and Quality Control in masonry construction.

In general, the Code is written as a legal document, which is suitable for adoption by the IBC; the Specification is written as a master Specification which is required by the Code and is meant to be modified and referenced on a projectspecific basis.

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implying that Quality Assurance Levels 2 and 3 will be specified and utilized by the Structural Engineer.

Table 3. Inspections.

MINIMUM SPECIAL INSPECTION

General Notes Simplified Structural Engineers are rightfully concerned that the project documents, including the General Notes, are complete, coordinated, and clearly communicate the design intent. Utilizing the Quality Assurance tables provided in TMS 602 will not only provide a complete task list for Quality Control but also will deliver a more consistent message for the inspector and contractor to accurately understand what is required to comply with the Quality Assurance plan set forth by the engineer.

The 2016 version of TMS 602 went a step further in combining all Quality Assurance levels into a single table. Now, the Structural Engineer has the option of utilizing the Verification and Inspection tables in their General Notes, in their entirety, with a statement of which Quality Assurance Level (1, 2 or 3) is required for compliance (Tables 2 and 3). When field personnel receive the same set of code-conforming requirements for every job, understanding and applying those requirements will improve dramatically.

The Structural Engineer may enhance the requirements, such as making some of the periodic tasks continuous or scheduling how much periodic inspection is required.

Conclusion

Inspection Task

John Chrysler is Executive Director of the Masonry Institute of America and current Chair of TMS 402/602 Committee. (jc@masonryinstitute.org)

18 STRUCTURE magazine

Level 1

Level 2

Level 3

a. Proportions of site-prepared mortar

NR

P

P

b. Grade and size of prestressing tendons and anchorages

NR

P

P

c. Grade, type and size of reinforcement, connectors, anchor bolts, and prestressing tendons and anchorages.

NR

P

P

d. Prestressing technique

NR

e. Properties of thin-bed mortar for AAC masonry

NR

f. Sample panel construction

NR

P

C

a. Grout space

NR

P

C

b. Placement of prestressing tendons and anchorages

NR

P

P

c. Placement of reinforcement, connectors, and anchor bolts

NR

P

C

d. Proportions of site-prepared grout and prestressing grout for bonded tendons

NR

P

P

a. Materials and procedures with the approved submittals

NR

P

P

b. Placement of masonry units and mortar joint construction

NR

P

P

c. Size and location of structural members

NR

P

P

d. Type, size, and location of anchors including other details of anchorage of masonry to structural members, frames or other construction.

NR

P

C

e. Welding of reinforcement

NR

C

C

f. Preparation, construction, and protection of masonry during cold weather (temperature below 40°F (4.4°C)) or hot weather (temperature above 90°F (32.3°C))

NR

P

P

g. Application and measurement of prestressing force

NR

C

C

h. Placement of grout and prestressing grout for bonded tendons is in compliance

NR

C

C

i. Placement of AAC masonry units and construction of thin-bed mortar joints

NR

C(b)/P(c)

C

NR

P

C

1. As masonry construction begins, verify that the following are in compliance:

P

P

C /P (b)

(c)

C

2. Prior to grouting, verify that the following are in compliance:

3. Verify compliance of the following during construction:

Masonry Verification and Inspection Tables are contained in TMS 602, Specification for Masonry Structures, a consensus document maintained by a balanced committee of users (designers), producers (industry representatives), and general interest stakeholders (academia and others). Committee members spend countless hours developing and maintaining the document, including the Verification and Inspection Tables. Quality Assurance and Quality Control provisions are regularly evaluated and reevaluated to ensure that the provisions harmonize with current applicable Standards and other provisions and that they are published for reference into the model building code. By simply incorporating these tables into the General Notes, the Structural Engineer will have a level of confidence that the intent of the Quality Assurance program will be understood and uniformly applied.■ Jefferson Asher is a Managing Principal with KPFF Consulting Engineers in Los Angeles, CA. Asher is Past-President/Chairman of the Board of KPFF. (jeff.asher@kpff.com)

Frequency(a)

4. Observe preparation of grout specimens, mortar specimens, and/or prisms.

Frequency refers to the frequency of inspection, which may be continuous during the listed task or periodically during the task listed, as defined in the table. NR = Nor Required, P = Periodic, C= Continuous (b) Required for the first 5,000 square feet (465 square meters) of AAC masonry. (c) Required after the first 5,000 square feet (465 square meters) of AAC masonry. (a)

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structural PRACTICES Successful Detailing for Hot-Dip Galvanizing

By Alana Hochstein

B

atch hot-dip galvanizing (HDG) after fabrication, a total immersion process in molten zinc, has a more than a 150-year track record of providing corrosion protection for steel in the harshest environments. Though primarily known for corrosion resistance, hot-dip galvanizing following ASTM A123, Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products, is increasingly specified for low initial cost, durability, longevity, availability, versatility, sustainability, and aesthetics. To achieve these additional benefits, there are several areas where structural engineers and detailers can work together to ensure steel pieces are successfully fabricated to achieve maximum galvanizing quality without negatively impacting structural integrity. The best practices specific to hot-dip galvanized steel may be unfamiliar to structural engineers and detailers experienced in other methods of corrosion protection, but an upfront effort to incorporate these details will pay dividends in terms of reduced cost, quick turnaround, and optimal quality. This article summarizes key topics which have the most significant impact on the quality of hot-dip galvanizing for general corrosion protection, Architecturally Exposed Structural Steel (AESS), painting or powder coating after hot-dip galvanizing, and fireproofing.

Impact of HDG Process Temperature Studies investigating common structural steel grades confirm the hot-dip galvanizing process produces no significant changes in the

Overlapping surfaces.

20 STRUCTURE magazine

mechanical properties of the steel, but certain practices will reduce or eliminate concerns related to the galvanizing temperature (approximately 830 degrees F).

For example, when steel is immersed in the galvanizing kettle, the change in temperature affects areas with increased residual stress from severe cold working. Parts that are severely cold-worked reduce the steelâ&#x20AC;&#x2122;s ductility and increase the potential for cracking during hot-dip galvanizing due to strain-age embrittlement, the Holes for vertical and angled tube trusses. effects of which are accelerated at the galvanizing temperature. Designers and Venting and Drainage Details steel detailers can incorporate best practices to reduce stresses induced during bending, As hot-dip galvanizing involves the immerhole-punching, rolling, and shearing prior to sion of steel in a series of process tanks, it is hot-dip galvanizing to avoid these concerns. critical to ensure the free flow of pretreatRecommendations for design best practices, ment solutions, air, and zinc so a smooth minimum bend diameters, and thermal treat- and uniform coating is achieved. Improper ments to relieve internal stresses are found venting and drainage details can result within ASTM A143, Standard Practice for in poor appearance, bare spots, excessive Safeguarding Against Embrittlement of Hot- build-up of zinc, blowouts, or danger to Dip Galvanized Structural Steel Products and plant personnel. To optimize galvanizing Procedure for Detecting Embrittlement. quality, ASTM A385, Standard Practice The galvanizing process temperature can also for Providing High-Quality Zinc Coatings impact susceptible fabrications, which may (Hot-Dip), provides preferred venting and distort as a result of relieving stresses induced drainage details for poles, handrails, trusses, during steel production and fabrication. ASTM tanks, gusset plates, stiffeners, end-plates, A384, Standard Practice for Safeguarding and bracings. Most venting and drainage Against Warpage and Distortion During Hot- details do not impact structural integrity or Dip Galvanizing of Steel Assemblies, identifies design function, but occasionally the prefactors and types of fabrications prone to dis- ferred hole sizes and placements may not be tortion as they experience different thermal suitable for assemblies or trusses when large expansion and contraction stresses in holes are placed on the sides of load-bearing addition to uneven heating and cooling members. Alternative hole details provided during angled immersion into the gal- in ASTM A385, in addition to direct comvanizing kettle. Specifically, light gauge munication with the detailer and galvanizer, material (20 gage to < Âź inch) welded can lead to a suitable substitute, sometimes or riveted to plate, bars, or angles tend to at the expense of aesthetic quality or overall distort, as do a-symmetrical pieces and corrosion protection. fabrications containing different material thickness that heat and cool at different Material Size and Shape rates. Distortion is primarily mitigated through design measures found within Galvanizing kettle dimensions limit the size of ASTM A384 to avoid high internal articles which can be fully coated. The average stresses and steel details for temporary galvanizing bath is 40 feet long, but 55- to or permanent bracing to provide stability 60-foot-long baths are common. Oversized during the inevitable thermal expansion articles are designed in modules, galvanized and contraction cycles. separately, and joined by bolting or welding.

Rust bleeding.

Bolted Structural Connections The components of a bolted connection, including nuts, bolts, or studs, are sent to the galvanizer when disassembled. Components with male threads are galvanized normally, while nuts and holes are provided an increased thread size after galvanizing to accommodate the increased bolt thread diameter that results after application of a thick galvanized coating.

Oversizing guidelines for interior threads for galvanizing are detailed in Table 5 of ASTM A563, Specification for Carbon and Alloy Steel Nuts.

For bearing type connections, the presence of a hot-dip galvanized coating on the contact surfaces is not detrimental to performance and does not affect design strength. Section J3.2 of the AISC Manual of Steel Construction: Load and Resistance Factor Design (LRFD manual) states oversized holes are not to be used in bearing type connections, but hole interior may require unblocking or cleaning after galvanizing to ensure bolt placement.

Welded Connections It is possible to weld after HDG using all conventional welding techniques with no impact on overall structural design.

However, when assemblies are welded prior to HDG, there are recommended design and detailing practices to ensure adequate corrosion protection and structural integrity.

It is best practice to avoid designs such as back-to-back channels with narrow gaps between overlapping surfaces to be welded.

Less viscous pretreatment solutions enter the gap between these surfaces, but zinc cannot enter gaps less than 3⁄32-inch-wide.

Trapped fluids or air will superheat to gas at the galvanizing temperature and may result in destructive pressures or weld blowouts.

Otherwise, the internal surfaces uncoated by zinc will eventually weep out of the gap with unsightly rust stains. Such areas need to be sealed using silicone caulking or an epoxy sealer to prevent weepage.

Where overlapping surfaces are unavoidable, the engineer should be involved and informed regarding the options for steel details listed in ASTM A385 to avoid these concerns. When the gap between overlapping surfaces is less than 3⁄32-inch-wide, fully seal-weld these areas to prevent the access

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Alternatively, progressive dipping (dipping each end of the article sequentially) is used to fully coat articles nearly double the bath dimensions. However, progressive dipping results in uneven heating and cooling of the material since only a portion of the article is immersed in molten zinc while the other is exposed to cooler air. This results in different expansion rates for the upper and lower part of the component, which may distort the article. Distortion can be mitigated by confirming lifting arrangements with the galvanizer, requesting increased venting and drainage to allow quick immersion and withdrawal from the galvanizing kettle, and designing for thermal expansion conditions.

Specifically, welds and constrained or framed portions of an assembly must be designed to handle the increased stresses from thermal expansion at the galvanizing temperature.

For slip critical connections, galvanized steel offers a lower slip coefficient than bare or mild steel and therefore decreased slip resistance. Clearance holes sized 1⁄8 inch larger than the nominal bolt diameter are acceptable for slipcritical connections and accommodate galvanized bolts without hole clearing.

Standard clearance holes are already sized 1 ⁄8 inch larger for bolts sized 1 inch or greater, but this same increase results in an oversized hole for bolts sized less than 1 inch in diameter. When oversized holes are used, a further reduction in slip capacity due to the reduction in the connection area ensures slip does not occur.

As the design slip resistance is reduced 15% for connections using oversized throughholes, this leads to additional bolts in the connection design.

Where painted or black steel faying surfaces are required to achieve a higher slip resistance, the HDG coating is ground off in the field, or a masking material is applied before galvanizing to prevent coating formation. Suitable masking materials include acid-resistant or high-temperature paints, tapes, greases, and thread compounds. Alternatively, zinc-silicate paints are applied to galvanized faying surfaces to increase the slip coefficient without coating removal.

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N O V E M B E R 2 019

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Galvanizing roughness.

of cleaning fluids. However, seal-welding can inadvertently affect the structural behavior of the welded components, and the use of seal-welding requires a variance to comply with AWS D1.1, Structural Welding Code – Steel. Alternatively, the detailer may specify stitch welding when the gap is at least 3⁄32 inch.

Although this method provides full corrosion protection to the interior area, the engineer should be consulted to confirm if a full seam weld is required for structural purposes.

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Because the initial appearance of HDG is challenging to predict, a uniform finish can be difficult to achieve without significant cost to remedy common surface conditions unsuitable for AESS members (roughness, runs, excess zinc). To facilitate communication and minimize the cost, Section 10 of the AISC Code of Standard Practice describes a categorical approach for AESS members based on viewing distance and type/function of the structure. To achieve the elevated standards of each AESS category, the AESS Custom category can be used to incorporate additional details to maximize aesthetic quality.

For example, abrasive blast cleaning of the steel before galvanizing, per SSPC SP 6/ NACE No. 3, is not required for standard structural steel but is the specified minimum

for AESS and will significantly improve the appearance of assemblies containing multiple steel chemistries and steels of chemical compositions outside the recommended ranges for galvanizing listed in ASTM A385. Next, galvanized AESS projects will also benefit from additional attention to cut edges. Flame, plasma, or laser cutting increases hardness and alters the diffusion properties near the cut edge, either making it difficult to develop a coating or resulting in a thick coating which is prone to delamination. For all AESS categories, grind thermally cut edges up to 1⁄16 inch. Finally, direct communication with the engineer and galvanizer to determine placement, quantity, and size of vent and drain holes in relation to the lifting orientation can help maximize aesthetics without impacting structural integrity.

Duplex Systems A duplex system involves applying paint or powder coating over the hot-dip galvanized coating to achieve desired aesthetics or increased longevity. ASTM D6386, Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Painting, provides the standard practices to prepare galvanized surfaces for painting. Instructions are included for smoothing, cleaning, and profiling the surface based on the identified initial surface condition. Meanwhile, ASTM D7803, Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Powder Coating, contains similar practices for powder coating. These specifications list surface conditions, such as zinc runs and rough coatings, which present challenges when the part is duplexed.

Passive Fireproofing

Some passive fireproofing materials require additional preparation to achieve a particular bond strength when Software based on the AISC Design Guide 11 2nd Ed. applied over galVibrations of Steel-Framed Structural Systems Due to Human Activity vanizing.

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identically to a duplex system. When applying spray-applied fire-resistive materials (SFRMs) over galvanizing, pre-application of mechanically fastened galvanized metal lath or the use of a bonding agent may be required. Further recommendations will vary by fireproofing manufacturer.

Resources for Hot-Dip Galvanizing Detailing Most design best practices and steel details necessary for successful galvanizing are readily available and easily adopted from the supporting ASTM specifications referenced throughout this article.

To better navigate and visualize the information contained in these galvanizing standards, the American Galvanizers Association (AGA) publication Design of Products to be Hot-dip Galvanized After Fabrication and the National Institute of Steel Detailing (NISD) publication, Hot-Dip Galvanizing: What We Need To Know, contain a wealth of practical examples and standard reference tables. Additionally, the AGA publication Recommended Details for Hot-dip Galvanized Structures provides working drawings with details for commonly galvanized components.

Early Communication A basic understanding of the hot-dip galvanizing process, recommended steel details, and a review of the above considerations are key to producing a high-quality galvanized coating. However, do not underestimate the value of discussing elevated standards or unique elements of a project with the galvanizer and fabricator directly. Establishing open lines of communication early on in the design process is the best way to maximize aesthetics for the corrosion protection of AESS members, duplex systems, passive fireproofing, and more. These conversations are worth the extra time upfront to alleviate potential future headaches and will result in the fabrication of structures that will stand strong for decades without maintenance and impress future generations to come.■ The online version of this article contains references. Please visit www.STRUCTUREmag.org.

Alana Hochstein is the Senior Corrosion Engineer for the American Galvanizers Association (AGA), Centennial, CO. (ahochstein@galvanizeit.org)

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NORTHRIDGE

25 YEARS LATER

Nonductile Concrete Frames

By Keith D. Palmer, Ph.D., S.E., P.E.

T

he Northridge earthquake struck the greater Los Angeles area during the early morning hours of January 17, 1994.

The earthquake was responsible for approximately 60 deaths, more than 9,000 injuries, and an estimated $20 billion in damages.

Significant ground shaking occurred over a wide area and exceeded design code values in many locations. Numerically, most of the damage was to wood-frame residences, but upwards of 200 concrete buildings were red-tagged. The Northridge earthquake was the first big test of pre-1980 concrete buildings and post-1980 buildings designed using updated code provisions following the 1971 San Fernando earthquake. The 1971 San Fernando earthquake exposed the deficiencies of the building codes in place at the time, particularly related to concrete. The collapses of the Olive View Medical Center and the Veterans Administration Hospital that occurred as a result of the San Fernando earthquake are famous examples of the hazards posed by “nonductile” concrete (NDC) buildings. Several of these NDC buildings collapsed or were severely damaged during the Northridge earthquake as well, including the Kaiser Permanente Office Building (Figure 1) and Saint John’s Hospital. This article discusses building code provisions for concrete structures, the performance of non-ductile concrete frame structures in the Northridge earthquake, associated changes made to the building code after, and retrofit ordinances being considered today for existing non-ductile concrete buildings.

Seismic Code Background Seismic building codes are continually evolving based on new information gained through research and observation of building performance during earthquakes. The great 1906 earthquake prompted the City of San Francisco to include earthquake design load requirements for buildings. In July 1959, the SEAOC Seismology Committee published the first edition of the Blue Book, officially titled Recommended Lateral Force Requirements. This “code” was the first to formalize the relationship between earthquake demands, building period, and the ductility of the lateral-forceresisting system. Preference was given to moment-resisting space frames for lateral resistance relative to bearing walls through 24 STRUCTURE magazine

the use of a lower “K” factor, which can be thought of as proportional to the inverse of the “R” factor in ASCE 7.

Meanwhile, researchers and practitioners were beginning to understand the advantages of ductile behavior and began testing and quantifying Figure 1. Kaiser Permanente. Source: NISEE-PEER, University of California, Berkeley. ways to provide ductility in concrete structures. In 1961, 5) Weak columns – strong beams.

Blume, Newmark, and Corning published 6) Slab-column punching shear.

Reinforced Concrete Buildings for Earthquake 7) Plan or vertical irregularities resulting Motions. The book provided design methods in torsion or soft or weak stories. and detailing principles for ensuring ductile behavior such as maximum allowable Damage to Concrete steel percentages, providing closely-spaced Frame Buildings closed ties in columns and beams, and providing continuous top and bottom steel for The damage caused to pre-1980 concrete stress reversals. Unfortunately, the concept buildings by the Northridge earthquake was of a ductile moment-resisting frame did significant but not a surprise. In general, prenot find its way into codes until the 1967 1980 shear wall buildings met life safety and Uniform Building Code (UBC). However, collapse prevention performance objectives. ductile frames were required only for buildThe Sherman Oaks Towers was a 12-story ings greater than 160 feet in height. These building designed to the 1964 Los Angeles provisions required smaller tie and stirrup City Code. The structure comprised flat-slab spacing along the lengths of moment frame floors and relatively symmetric concrete shear columns and beams, respectively, and special walls, on the perimeter and surrounding the transverse joint reinforcement. elevator core. Damage consisted primarily of The San Fernando earthquake provided shear wall boundary element failure due to the impetus to update code requirements to the lack of closely-spaced confinement reinensure the ductile behavior of concrete struc- forcement. The building was yellow-tagged tures, and the 1976 UBC is considered to be but was repaired relatively quickly with epoxy the first code to provide seismic resistance of injection of the cracks and installation of steel concrete buildings similar to current code. straps at the location of the wall boundary Given the lag in construction year relative to element failures. design year, the benchmark that most engiPre-1980 frame buildings typically fared neers use for determining if a building is likely worse than their shear wall counterparts.

NDC is 1980.

The Holiday Inn in Van Nuys was a sevenThe most common types of deficiencies in story concrete frame structure built in 1966.

NDC buildings include: The frames consisted of exterior column1) Beam and column stirrups and ties spandrels and interior flat slabs. Minor spaced relatively far apart, causstructural damage occurred during the San ing shear failures and lack of core Fernando earthquake but was repaired using confinement. epoxy injection and patches. The building 2) Use of 90-degree bends on closed stir- was red-tagged following the Northridge rups instead of 135-degree hooks. event and required temporary shoring for 3) Lack of joint shear reinforcement. fear of collapse. The major damage mainly 4) Inadequate lap splices and locating consisted of column shear failure below them in regions of high flexural stress. the fifth floor due to lack of ties (Figure 2),

Figure 2. Holiday Inn, Van Nuys. Source: NISEEPEER, University of California, Berkeley.

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which led to significant spalling and buckling of the longitudinal reinforcement. The building was later retrofitted with concrete shear walls.

Champaign Tower is a 15-story concrete building in Santa Monica and experienced extensive perimeter column damage due to deep parapets on the balconies. This “shortcolumn” behavior results from high shear demands that the columns attract due to their high stiffness. The coupling beams in the shear walls in the orthogonal direction also experienced significant shear damage.

Surprisingly, the damaged columns were still able to maintain gravity load resistance.

Saint John’s Hospital is another building located in Santa Monica and consisted of several buildings, built between 1942 and 1966, that were damaged. The Main Wing and the South Wing were yellow-tagged, and the North Wing was red-tagged and demolished. The North Wing lateral system comprised perimeter punched concrete walls.

Significant shear cracking occurred in the piers and spandrels at the second floor. There was less wall at this level than the one above, resulting in a likely weak-story. Additionally, the piers were relatively short in many locations creating a “short-column” condition.

Taller piers at the second floor did not experience shear cracking.

Much of the column damage and collapses were caused because the columns, designed for gravity loads only, were not detailed to accommodate the displacements they would undergo during an earthquake. As a result, shear failures occurred and did not provide

proper confinement for the longitudinal reinforcement, causing loss of gravityload carrying capacity. Similarly, damage occurred in frame buildings that utilized flat slab floor construction that was not designed to accommodate large displacements and the shear demands imposed on them at the column. A flat slab building with perimeter moment frames in the Sherman Oaks area is one such building.

Slab damage, including spalling and concrete crushing, was observed on the top and underside at the columns around the outline of the drop panel. This building was red-tagged by the city. A few similar failures were also observed in residential concrete podium garages with wood structures above.

Several buildings and parking garages saw partial or total collapse, including the Kaiser Permanente Office Building (Figure 1) in Northridge and two garages at the Northridge Fashion Center. The Kaiser collapse was attributed to inadequate confinement in the columns and shotcrete shear walls inadequately attached to the frame. The Northridge parking garages were relatively new structures (circa 1988) but were constructed of precast double and inverted tees. Failure was attributed to large diaphragm movements causing the failure of gravity columns that lacked proper confinement. Additionally, large out-of-plane displacements of the perimeter frames occurred causing the precast beams to unseat. Collector failures were also observed in the topping slabs of precast decks in the vicinity of shear walls.

A large percentage of rigid-wall-flexiblediaphragm buildings were also damaged.

These buildings typically comprise walls cast on the ground and tilted up into position with a panelized wood roof system. Several roof collapses occurred due to failures of the connection between the tilt-up panels and diaphragm (See the past STRUCTURE article, April 2019, by Lawson and McCormick).

In general, post-1980 and retrofitted buildings performed as intended with a few exceptions. A retail facility in Topanga Plaza, constructed in the early 1960s, was retrofitted in 1989 through the addition of shotcrete walls. These walls were attached to the existing walls with dowels designed to transfer the calculated seismic forces. The new walls were designed to resist seismic load in tandem with the existing walls. More damage occurred in the new walls; the existing walls exhibited sliding shear failures at the base, transferring most of the load to the new walls. Additionally, many of the cracks in the new walls occurred along horizontal

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Following the earthquake, significant field investigations and studies were performed by structural engineers that resulted in several recommendations to improve the performance of concrete buildings. The UBC was published every three years, but interim changes are often produced; several changes directly related to the failures observed in Northridge were implemented in the 1996 UBC Supplement.

1) The strength-reduction factor for reinforcement used for diaphragm chords and collectors in topping slabs over precast concrete members was reduced to 0.6 from 0.7.

2) Minimum thickness of topping slabs placed over precast floor and roof elements was increased from 2.5 to 3 inches or 6 times the diameter of the largest slab reinforcing bar.

3) Spacing limits and transverse reinforcement requirements were added for chord and collector reinforcement at splices and anchorage zones.

4) The coupling beam definition was expanded to include all beams connecting walls regardless of the span/ depth ratio. Additionally, a maximum shear strength limit of 10√f'c was added, along with the requirement that longitudinal bars be enclosed with transverse reinforcement.

5) Allowance of smaller amounts of reinforcement in compression members with a cross-section larger than required for loading was removed for members in Seismic Zones 3 and 4.

6) Stricter requirements were implemented for frame members not part of the lateral system. Tie spacings were reduced for members with induced moments and shears (from 3(Rw/8) times the displacements) that do not exceed the design moment and shear strength of the member.

Additionally, when the axial load in those members exceed 30% of the design axial strength, they must be reinforced according to the provisions for lateral frame members.

The City of Los Angeles/SEAOSC Task Force also recommended that DBS survey and identify all concrete structures constructed before 1976 and develop a mandatory retrofit ordinance. As discussed below, the ordinance has finally been implemented albeit 25 years later.

Current Status Modern standards such as ASCE 7, Minimum Design Loads for Buildings and Other Structures, and ACI 318, Building Code Requirements for Structural Concrete, contain the requirements for concrete structures designed for seismic resistance. The information provided represents a vast body of knowledge gained through observations after earthquakes and theoretical and experimental research performed at universities. However, there are still thousands of pre-1980 NDC buildings in high seismic regions in the U.S. and abroad. The California Seismic Safety Commission estimates that there are 40,000 in California. The SEAONC Existing Buildings Committee, in cooperation with EpiCenter, recently completed an inventory based on all Sanborn maps for the City of San Francisco. The inventory resulted in an estimate of 3,400 pre-1980 concrete buildings, verifying the estimate calculated by the Concrete Coalition. The risk of these buildings has not been accurately quantified and is difficult given the variability of building configurations, system types, and a frequent lack of drawings. Methodologies to determine the risk of these buildings include ASCE 41, Seismic Evaluation and Retrofit of Existing Buildings, Tiers 1, 2, and 3, and the recently developed methodology for ranking buildings in an inventory, ATC 78, Seismic Evaluation of Older Concrete Frame, FrameWall, and Bearing Wall Buildings for Collapse Potential. Several Southern California cities have recently adopted ordinances that require owners to assess the collapse potential of their older concrete buildings and retrofit these if the assessment deems this necessary. These cities include the City of Los Angeles, West Hollywood, and Santa Monica. San Francisco is currently deciding what to do about the NDC building stock in the city. The knowledge to design and retrofit concrete buildings safely currently exists. Hopefully, the current stock of NDC buildings will be able to be economically retrofitted before the next big one hits.■ The online version of this article contains references. Please visit www.STRUCTUREmag.org.

Keith Palmer is a Senior Project Manager in the San Francisco office of Simpson Gumpertz & Heger. He is the current Chair of the Existing Buildings Committee of the Structural Engineers Association of Northern California and the Co-Chair of the Nonductile Concrete Subcommittee. (kdpalmer@sgh.com)

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INSIGHTS Masonry Testing Technician Certification

Raising the Bar for Testing and Quality Assurance

By Nicholas R. Lang, P.E.

I

t is a familiar situation for anyone who has been involved in a masonry construction project. Things have progressed through design, bidding, and contracting, and are in the construction phase. One day, as part of the specified quality assurance program, a testing laboratory technician visits the job, samples materials, and takes them away for testing.

Sometime later, usually after 28 days, the dreaded call is made – the materials are not compliant. The project shuts down, meetings ensue, and further evaluation, usually costly destructive testing, is performed. Finally, additional testing shows satisfactory results and the project resumes. However, this process has caused significant lost time and testing.

There can be ways to reduce the frequency of situations such as the ones described above. A crucial part of improving quality assurance and testing of masonry products is ensuring the person performing the testing is knowledgeable about masonry testing procedures and is qualified to perform this testing. A relatively new tool for qualifying technicians is the American Concrete Institute (ACI) Masonry Testing Technician Certification Program. Developed by ACI in conjunction with industry experts from The Masonry Society (TMS), Portland Cement Association (PCA), and the National Concrete Masonry Association (NCMA), this program provides a mechanism for testing technicians to be certified to test masonry products.

Why is Testing Necessary?

It is important to understand why testing of masonry products is necessary. Testing can be performed for a wide variety of reasons, such as product development, quality control on behalf of the manufacturer, and compliance with various specifications. When performed on a specific project, testing is usually part of the overall quality assurance program.

As defined by masonry building codes, quality assurance is “The administrative and procedural requirements established by the contract documents to assure that constructed masonry is in compliance with the contract documents.” There are three levels of masonry 28 STRUCTURE magazine

quality assurance programs.

The level for a given project is defined in TMS 402, Building Code Requirements for Masonry Structures. The level required depends on Nicholas Lang of the National Concrete Masonry Association discusses the type of design used as critical measurement verifications for concrete masonry units. well as the Risk Category for the building. For example, an empirically Scope of Certification Program designed structure in Risk Category I, II, or III requires Level 1 Quality Assurance; while There are two separate certification a building designed using Strength Design in programs; the Masonry Field Testing Risk Category IV requires Level 3 Quality Technician (MFTT) program, which is Assurance. designed to evaluate technicians sampling The requirements for each level of quality and testing in the field, and the Masonry assurance are found in TMS 602, Specification Laboratory Testing Technician (MLTT) for Masonry Structures. The quality assurance program, which evaluates the knowledge program can contain a variety of things, from of technicians who test materials in the a review of project submittals to inspection laboratory. The test methods for determining requirements to testing. All levels of masonry properties of masonry materials have been quality assurance require at least some mate- developed through ASTM International. rial testing. Ensuring that this testing is done Many of these standards have both field properly, in accordance with ASTM standards and laboratory components. Because of and test methods, is of utmost importance. this, there is overlap in the actual methods Depending on the applicable level of quality between the two certification programs, assurance, tasks related to material evaluation although there is no overlap of actual and testing from TMS 602, Table 3, include: content. The MFTT program evaluates • Prior to construction, verify f´m and knowledge based on the field components f´AAC unless exempted by code of the relative standards, and the MLTT • During construction, verify grout program evaluates knowledge based on the slump flow and Visual Stability Index lab components. for self-consolidating grout The ASTM standards used by the programs are: • During construction, verify f´m and f´AAC • ASTM C67 – Sampling and Testing for every 5,000 square feet of masonry Brick and Structural Clay Tile • During construction, verify propor(MFTT only) tions of materials for preblended • ASTM C90 – Loadbearing Concrete mortar, prestressing grout, and grout Masonry Units (MLTT only) other than self-consolidating grout • ASTM C140/C140M – Sampling and Unfortunately, testing of masonry materials Testing Concrete Masonry Units and is sometimes performed incorrectly. This is Related Units (MFTT & MLTT) primarily due to a lack of familiarity with specific • ASTM C270 – Mortar for Unit testing requirements for masonry. Testing labs, Masonry (MLTT only) in general, are usually more familiar with testing • ASTM C780 – Preconstruction and for poured concrete, and there are some specific Construction Evaluation of Mortars differences in how masonry materials are tested. for Plain and Reinforced Unit Masonry The goal of the ACI Masonry Testing Technician (MFTT & MLTT) Program is to evaluate the knowledge of • ASTM C1019 – Sampling and Testing individuals on the proper testing requirements Grout (MFTT & MLTT) and to recognize those that demonstrate • ASTM C1314 – Compressive Strength command of that knowledge. of Masonry Prisms (MFTT & MLTT)

• ASTM C1552 – Capping Concrete Masonry Units, Related Units and Masonry Prisms for Compression Testing (MLTT only) These test methods were selected because they are the ones most commonly performed on masonry materials. For some methods, such as ASTM C140/C140M, only part of the standard is covered. ASTM C140/ C140M contains test methods for a wide variety of concrete masonry products, including concrete masonry units (CMU), concrete pavers, segmental retaining wall units, and more. The certification, however, only covers testing of CMU. CMU is the product tested most frequently by a wide variety of laboratories and is required for quality assurance on many projects by TMS 602. Future certification programs may cover more products and methods.

Developing a Certification Program Once the need for a program is identified, the first step in development is to create a committee. The committee that was tasked with developing this program was ACI 601-C, chaired by Chris Robinson, Executive Director of the Construction Materials Engineering Council in Orlando, FL. This committee was populated with subject matter experts, industry representatives, and testing laboratory personnel. Many interested industry groups were represented and provided support for developing the program: The Masonry Society (TMS), the National Concrete Masonry Association (NCMA), the Portland Cement Association (PCA), and others. TMS took a leadership role in the development and subsequent promotion of the program.

Once the overall scope of the programs, including the test methods listed above, was developed, the next step was to create a Job Task Analysis (JTA). The JTA is a step-bystep walkthrough of a test method, describing in detail the knowledge and skills needed for a technician to perform the work required by the test. Since both certification programs include both a written examination and a performance examination, the JTA identifies the information that a technician needs to know (and is evaluated in the written exam) and those items that are a skill (and is evaluated in the performance exam). Once the committee approves this JTA, exam development begins.

The committee developed a sizable bank of written examination questions that covered the breadth of knowledge for each test method. The question bank was 2-3 times as large as needed for any given exam so

that the questions can be varied for different exam offerings. For the performance exam, checklists were developed that detail each step in the test method. These checklists are used by examiners during the test to ensure that examinees cover all needed steps and demonstrate proficiency in each one.

Following development, ACI staff audited all materials to ensure that questions were fair and instructions were satisfactory. From there, two pilot programs were held in different locations in the U.S. The feedback from the pilot programs was used to refine details of the program further.

Finally, after several years of development, the program was approved by ACI’s Committees and offered to all interested parties.

Becoming Certified In order to become certified, an interested individual needs to find a sponsoring group that is offering the program. TMS is a National Sponsoring Group and provides the program in locations around the U.S. on request. In addition, local chapters of ACI (located in the U.S. and throughout the world) may offer the program. The best way to find a class is to check with TMS (www.masonrysociety.org) or a local ACI chapter.

Many sponsoring groups offer optional education/review sessions to help prepare examinees, but there are no required prerequisites for the certifications. The written examination is broken into sections for each test method. A minimum score of 70% overall is required, as well as at least 60% on any individual section, to pass the written exam.

For the performance examination, each test is performed. The examinee must achieve 100% on each of the methods, and they have two trials for each method.

Both the written and performance component must be completed in order to achieve certification. This ensures that the technician not only has sufficient knowledge but has the ability to perform necessary testing skills. The certification is good for 5 years, at which time the individual must re-certify by passing the exams again.

The program is maintained regularly by ACI Committee C670, which is comprised much like the original development committee, with representation by testing labs, industry groups, subject matter experts, and other interested parties.

Increasing Demand For a certification program to be successful, there must be demand. These certification programs have been available since late 2014.

In many aspects, they are still in the early stages of adoption.

There is an identified need for a certification program based on experiences with improper testing and job site problems, as discussed earlier in this article. This primarily relates to field technicians; however, there must also be an incentive for laboratory personnel to participate. The 2016 version of TMS 602 has a new requirement to “Utilize qualified laboratory technicians to perform required laboratory tests.” The commentary to the Specification lists the ACI certification programs, or equivalent, as a way to demonstrate that a technician is qualified.

With this version of TMS 602 adopted into the 2018 International Building Code, demand for these programs will increase.

Additionally, efforts are underway to require certified technicians with ASTM standards. ASTM C1093, Practice for Accreditation of Testing Agencies for Masonry, contains requirements for quality control and assurance for labs. The standard currently includes minimum experience requirements for lab personnel but does not contain certification requirements. The committee charged with maintaining this standard is actively evaluating changes to require certifications for testing personnel, and it is expected that this will be included in C1093 in the future.

Summary There is a demonstrated need for accurate testing of masonry materials used in construction. Proper equipment must be used, the correct procedures followed, and technicians must be knowledgeable and competent to assure this. The ACI Masonry Field Testing Technician and Masonry Laboratory Testing Technician programs were developed to address knowledge and competency. These programs evaluate the knowledge and skill of technicians on common masonry tests in both the laboratory and the field. Use of qualified, certified individuals will raise the level of testing quality for masonry materials and reduce instances of improper testing. All designers and specifiers are encouraged to require certified testing technicians for masonry testing.■

Nicholas R. Lang is the Vice President of Business Development for the National Concrete Masonry Association. He is an active member of ASTM International, The Masonry Society, and the American Concrete Institute. (nlang@ncma.org)

N O V E M B E R 2 019

29

Amherst College’s New Science Center enlivens the sciences on campus by allowing the community to see the work being done. Courtesy of Chuck Choi Architectural Photography.

When Science Becomes Transparent

By Adam Blanchard, P.E., and Jeffrey Abramson, AIA, LEED AP

“One of the defining features of this building is transparency. It really demystifies the sciences.”

– Amherst College Operations

T

he New Science Center (NSC) at Amherst College anchors In realizing the architectural vision of the Commons space, a structhe eastern edge of the bucolic hilltop campus in Amherst, tural scheme needed to be developed that would accommodate the Massachusetts. From overall organization to the finest detail, the multi-story, column-free space and would evince the feel of a living design of the NSC achieves transparency and interaction at every room serving the whole campus. By hanging the glass wall from the level. The surrounding landscape seamlessly meets the transparent roof structure, the wall mullions would be in tension and thus would glass façade of the Commons, blurring the edges of the central living require smaller sections to resist the design loads. Concurrent with room and creating a gathering space that feels like an extension of being in tension due to the self-weight of the steel and glass, the the outdoors. paired plate mullions of the glass wall are subjected to bending forces The glass façade of the Commons is a structural silicone glazed from the wind and seismic loads acting laterally. The tensile stress in curtain wall system comprised of triple-glazed insulating units and the paired plate mullions is analogous to a pre-tension of the steel an automated shading system which controls the glare and the overall so that, in bending conditions, the mullions remain in permanent lighting levels. The curtain wall is hung in tension from a steel roof net tension, thus negating the need for stability bracing. The base structure cantilevered up to forty feet over the Commons below. of the mullions are connected through two vertically slotted holes The structure supporting the curtain wall is comprised of a paired which allows the bending moment to be resisted – and resolved to steel plate assembly and steel tee profile which acts as the vertical lateral loads into the concrete slabs – while preventing any vertical mullion for the system. The approach to hang the system and design load forcing the mullions into compression. the structure as an assemblage of components, rather than a larger The structural system of the NSC is cast-in-place concrete throughout. single member, resulted in maximized transparency and transmis- However, the roof structure spanning over the Commons necessitated sion of daylight as it filters through the members to the interior. a steel frame to sustain the weight of the glass wall concurrently with The building’s primary unifying feature is the distinctive roof which cantilevering over the column-free Commons space. The columns covers the multi-story, glass-enclosed Commons and provides a quiet supporting the glass wall are nearly 40 feet removed from the curtain visual datum for the undulating Pelham Hills beyond. The roof performs many functions simultaneously: it provides both natural and artificial light, its photovoltaic panels generate electricity, and its shape and materials afford acoustic control, all while radiantly heating and cooling the Commons.

The steel roof structure, concealed within curvilinear glass fiber reinforced gypsum ceiling panels, is cantilevered from the exposed concrete structure of the lab wings over the Commons, which in turn Structural detail at the base of the glass wall and the connection View of the erected steel paired plate mullions and two-bolt to the concrete wall and slab. connection at the base of the glass wall. suspends the glass curtain wall.

30 STRUCTURE magazine

wall, supporting a load of nearly 10,000 to the varying stiffness of the cantilevers pounds per mullion in addition to the and the changing magnitude of the applied dead, snow, wind, and seismic loads. loads, leveling nuts were implemented The roof frame is comprised of cantilewhere the cantilevers were anchored to vered beams reaching from 32 to 40 feet columns. from its nearest support, each aligned These nuts, sometimes as far as 40 feet with a curtain wall mullion assembly. from the glass wall, allowed very fine Near the free end of each cantilever is adjustments to the initial position of the the connection of the curtain wall; each steel cantilevers by turning the nuts as connection sustains up to 10 kips. The much or as little as needed; a small adjustcantilevers are anchored to the tops of ment in the leveling nut would result in the concrete columns in the lab wing. a comparatively large repositioning of the Due to the programmatic need for an cantilever at the glass wall position. In this open lab environment, it was infeasible manner, each cantilever was able to be set to have columns spaced at the same at a pre-determined elevation before load5-foot-3-inch-rhythm of the roof steel. ing the steel with the glass wall. Selecting As a result, some of the cantilever steel the proper elevation to set the cantilevers roof beams were supported not directly required that the Glass Design-Assist by columns, but by girders spanning Structural detail of the cantilevered W36 roof beams with Contractor supply LeMessurier with the leveling nuts for adjustability throughout glass installation. between the columns. loads of the glass wall at each cantilever so Each roof cantilever supported variable that deflections could be predicted. This amounts of load, adding a layer of complexity to the already-variable would allow the steel to deflect to the datum elevation once the entire support conditions: cantilevers supporting the full 70-foot-high glass glass wall was suspended from the roof steel. The predictions of steel are flanked on each side – where the pavilions interact with the glass deflection were determined via a full finite element model of the roof wall – by cantilevers supporting loads for only a 10-foot height of frame, applying the glass reactions supplied by Novum Structures. glass. In some instances, beams supporting the highest and lowest loads were immediately next to one another; the relative stiffness of In-Situ Deflection Control adjacent cantilevers needed to be tailored on a one-by-one basis so that two conditions were met: Once the glass wall was hung from the roof steel, achieving a consistent 1) The top of the glass wall (i.e., the underside of steel) was at a horizontal datum across the roof, the differential deflection of adjacent constant elevation after the glass was hung. cantilevers needed to be controlled to limit the stress placed on the 2) No two adjacent cantilevers deflected more than ¼ inch difcaulking between adjacent panes of glass. By querying the roof finite ferentially under transient loads (wind, seismic, snow). element model, the section properties of the cantilevers were adjusted Because cantilevers holding different loads and consisting of varying to result in deflection characteristics across the entire roof such that supports will lead to different structural deflections, the two condi- no two adjacent cantilevers deflected by more than ¼ inch due to tions noted above needed to address both the initial position of the transient loads. This effort involved increasing the section properties cantilevers and the in-situ movements of the cantilevers. of some W36s (including custom built-up shapes) to decreasing the section properties of others and allow normalization of deflections at each cantilever location.

Initial Position – Adjustability Installation followed the careful planning and selection of the cantileW36 steel beams were selected for the cantilevers in all instances to vers. Barr & Barr engaged Structures Derek to erect the structural steel maintain consistent steel elevations, both at the top of steel for a flat with the task of setting each piece at its designated elevation. To achieve roof and the bottom of steel for a consistent datum for the glass wall; this, surveys were conducted frequently to provide continuous feedback this also allowed for a consistent length of glass wall mullions. Due about the position of the steel defining the datum at the top of the

Structural detail at the head of the glass wall and the connection to the cantilever beams.

View of the erected roof framing and curtain wall connection plates at the top of the wall.

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“This is the biggest transformation of the Amherst campus since its founding. It says that we care deeply about science, and it says the same thing about community, about our commitment to sustainability, about our commitment to beauty.” – AMHERST COLLEGE, PRESIDENT glass. As the cantilevers were tied together with secondary framing and roof deck, final adjustments were made to the steel before installing the glass. Once the roof was in its final connected condition, adjustments at Schematic section at Commons showing the one leveling nut resulted framing geometry of the column (right), in a proportional effect glass wall (left) and the roof cantilevers (top). on cantilevers on either side of the adjusted location. Surveys were conducted periodically through the installation of glass, and corresponding adjustments were made at the leveling nuts so that, at the end of glass installation, the steel had come into alignment across the entire length of the roof, precisely as planned.

Faced with an aging science center unable to accommodate today’s technologies, equipment, and pedagogies, Amherst sought a new, forward-looking building that would create an open learning environment for the entire campus community for the next 100 years.

By creating a Commons space that was welcoming, the desired effect of a living room had been brought to life inside the New

Science Center. The resulting glass wall, with its perfectly vertical and horizontal datum lines, underscored the close coordination of the entire project team. It was through this meticulous craft in design and construction that the driving forces of layered transparency and academic connectivity were achieved, and the campus fundamentally transformed for the future.■ Adam Blanchard is a Principal at LeMessurier and teaches at The Boston Architectural College. (ablanchard@lemessurier.com) Jeffrey Abramson is a Senior Associate at Payette. (jabramson@payette.com)

Project Team Owner: Amherst College, Amherst, MA Structural Engineer: LeMessurier, Boston, MA Architect: Payette, Boston, MA Construction Manager: Barr & Barr, New York, NY Structural Steel Contractor: Structures Derek, Sainte-Marie, Quebec, Canada Glass Design-Assist Consultant: Studio NYL, Boulder, CO Glass Design-Assist Contractor: Novum Structures Menomonee Falls, WI

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he University of Pennsylvania’s Ronald O. Perelman Center for Political Science and Economics (PCPSE) serves as a unified facility dedicated to global social science teaching and learning. It opened to students for the 2018-2019 academic year.

The $77.6 million project involved a 54,440-square-foot renovation and reuse of the historic 1925 West Philadelphia Title and Trust Co. Building with the construction of a new 56,700square-foot addition. Kuwabara Payne McKenna Blumberg Architects (KPMB) of Canada designed the project to integrate old and new. The combined facility contains a 120-seat auditorium, classrooms, collaboration areas, computing rooms, and faculty offices. LEED Silver Certification remains pending.

Exterior dusk view from 36th and Walnut Streets of the PCPSE on the University of Pennsylvania campus. Courtesy of Adrien Williams.

PERELMAN CENTER FOR POLITICAL SCIENCE AND ECONOMICS An Unlikely Pair: Steel Trusses and Flat-Plate Keast & Hood structural engineers of Philadelphia, PA, provided structural design for the project, led by Principal Constantine G. Doukakis, P.E., and Associate Allison Lukachik, P.E., S.E., C.D.T. Structural challenges involved a 30-foot-tall cantilevering steel feature stair, two 19-foot-tall steel transfer trusses to enable a columnfree lower-level auditorium, and the use of concrete flat-plate floor framing to compensate for low floor-to-floor heights in the West Philadelphia Title and Trust building. To further complicate efforts, no structural drawings existed for the original building, which featured two variations on an existing concrete-encased steel structure.

Through the use of 3-D structural analysis and team collaboration, the engineering solution applied structural gymnastics and more than a little creativity.

Existing Conditions Shortly after the West Philadelphia Title and Trust building opened in 1925, an addition was built. Mostly indistinguishable from the

34 STRUCTURE magazine

BY ALLISON LUKACHIK, P.E., S.E., C.D.T., AND AMANDA GIBNEY WEKO

exterior, the two separate campaigns revealed themselves through slight changes in the structural framing and discovery of a sizable rubble stone wall roughly separating the basement into halves.

Keast & Hood dug into historical archives maintained by the Athenaeum of Philadelphia and old city maps to confirm that not only was the building constructed as two sequential campaigns separated by only two years, but it was designed under two different architects. Unfortunately, drawings did not exist for either project, and the concrete-encased steel limited the engineers’ ability to gain much information via visual survey. The team used 3-D laser scan information and probes to understand the structure and identify beam sizes. Engineers found that the system changed slightly within the addition. Lightweight steel joist framing discovered at the second level revealed the original two-story banking space was infilled at some point. Although in good condition, the steel’s age meant it had limited strength. In locations where new usage necessitated higher loads, the concrete had to be removed, steel reinforcements added, and fire-resistive materials spray-applied to restore the fire rating.

Programmatic and Pragmatic Acknowledging the limits of the existing building structure to minimize the need for structural reinforcements, the team placed high-occupancy spaces in the new building and lower-occupancy rooms in the original bank building. The new forum was one exception to this approach where reinforcement of the 1927 framing was introduced.

The design removed a significant portion of the second-floor infill to recreate the original grandeur of the ground floor. Inserted within the void previously occupied by an old stair and elevator towers, a new feature stair provides access to the auditorium. A basement location for the auditorium worked best with circulation and ability to accommodate the depth of sloped seating. However, functionality as an auditorium necessitated a column-free room.

Keast & Hood considered post-tensioned concrete because it could achieve both the large span and meet the low floor-to-floor height of the existing building, but recognized its future limitations. Making penetrations in post-tensioned concrete requires care to avoid cutting tendons, which carry a large amount of force. While controlled de-tensioning is both possible and safe when done correctly, the process can be costly. Since the ceiling of the auditorium forms the floor plate of a large classroom and circulation above, engineers wanted to avoid potential limitations and ensure the University of Pennsylvania had the flexibility for future changes without requiring costly structural interventions.

When viewed in the context of the space and architectural objectives, steel proved the best solution.

Construction progress elevation view of long span, steel story truss with steel hangers down to the first-floor structure.

Transfer Trusses In the new portion of the building, two 19-foot-tall, 53-foot-long steel transfer trusses support four floors above and one floor below to enable the column-free basement auditorium. Steel beams frame between the trusses at the building’s first, second, and third levels, infilling the floor slab within the surrounding flat-plate concrete slab structure. The second floor frames into the bottom chords; the third floor frames into the top chords; and from the bottom, six steel hangers support the first floor. The concrete columns for floors four

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through seven and the roof bear on the trusses, which become integral to the structure of the entire building. These two trusses in effect support all levels of the building either through direct framing, hangers, or via columns that post up from their top chords.

stair assembly. Three-quarters to oneinch-thick steel plates serve double duty as the stair’s stringers and guard rails, giving the stair a sleek, industrial look.

These plates also provide the stiffness necessary to cantilever out 30 feet from the floor slab, with minimal deflection experienced under code-prescribed loading conditions, and to ensure vibraFlat-Plate Concrete tion issues common to feature stairs Most of the former bank building feadid not manifest. Challenges included tured floor-to-floor heights of 12 feet. determining depths into which strucTo accommodate comfortable ceiltural elements could be concealed, ing heights of nine to ten feet, and to understanding how the stair would avoid awkward shifts of floor heights be fabricated, and evaluating whether between the old and new parts of the the handrail would be used structurbuilding, Keast & Hood turned to flatally. Analysis efforts determined that plate concrete. The solution kept the the handrails were not required for the structure to the 12-foot ceiling height 3-D feature stair analysis model rendering created in Ram Elements. stability or reinforcement of the deep and accommodated mechanical, elecplate stringers, allowing their architectrical, and plumbing runs in the ceiling space without infringing tural expression to remain independent. The architecturally exposed on the already tight space. At column locations where punching steel also required careful detailing of welds for a clean visual appearshear was a concern, stud rails within the depth of the concrete slab ance. Engineers used RAM Elements to perform analyses. The team were utilized instead of large column drop caps, keeping the ceiling engaged stair engineer Providence Engineering Corporation of cavity open. Traditional steel with concrete slabs on deck would have Lancaster, Pa., who verified design and constructability, matching compromised too much head height, reducing the ceiling heights the structural team’s numbers exactly. to uncomfortably low positions.

Systems Integration The use of steel to span the auditorium and support the addition, and the use of flat-plate concrete in the addition, required detailing to ensure compatibility of the different systems. Integration with the existing concrete-encased steel structure further complicated the process. Engineers used several programs within the Bentley RAM software suite to perform analysis and eliminate potential conflicts.

Particular effort was made to manage and coordinate construction, including phasing between the two structural building trades.

Signature Stair A 30-foot-tall cantilevering steel feature stair connects three levels of the conjoined building. The signature staircase provides primary access to the basement auditorium. Here, structural gymnastics compensated for horizontal thrust at the floor levels and provided support for the cantilevered condition.

The stair cantilevers down from each floor like a sideways Z, attaches to the next floor, and cantilevers again. Sections of the slabs were removed and replaced with horizontal steel trusses that tie into the existing columns to deal with horizontal thrust at floor levels. These are capped with steel plates for support and aesthetic uniformity with the steel stair. The design eases the massive horizontal forces developed as a result of the cantilevered condition while not overstressing the slabs. A substantial concrete mass footing anchors the stair at the base and ensures horizontal loads do not transfer to the adjacent rubble stone basement wall of the existing building.

The stair solution required much collaboration between architects and structural engineers. Hidden horizontal tube steel trusses were incorporated at each landing to prevent twisting. Hidden steel tubes beneath the stair treads provide added support and stiffness to the

36 STRUCTURE magazine

Creativity and Collaboration The challenging constraints of the existing building inherited by the design team encouraged a high degree of creativity and collaboration that resulted in an impressive facility for the University of Pennsylvania.■ Allison Lukachik is an Associate with Keast & Hood in Philadelphia, PA. She served as Project Manager for the Perelman Center for Political Science and Economics structural engineering scope of work. (alukachik@keasthood.com) Amanda Gibney Weko is Principal of AGW Communications in Haddonfield, N.J. Trained as an architect, she writes for and about the built environment and is a longtime collaborator with Keast & Hood. (amanda.weko@agwdesigncommunications.com)

Project Team Owner: University of Pennsylvania, Philadelphia, PA Structural Engineer: Keast & Hood, Philadelphia, PA Architecture: Kuwabara Payne McKenna Blumberg Architects, Toronto, Ontario, Canada Construction Management: Hunter Roberts Construction Group, Philadelphia, PA Concrete Subcontractor: Healy Long & Jevin, Wilmington, DE Environmental Design and Energy Analysis: Atelier Ten, New York, NY MEP/Fire Protection Engineering and LEED Administration: AHA Consulting, Inc., Lexington, MA Stair Fabricator: Crescent Iron Works, Philadelphia, PA Steel Fabricator and Erector: Steel Suppliers Erectors, Inc., Wilmington, DE

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Hudson Commons INNOVATIVE APPROACHES TO VERTICAL EXPANSION

By Joseph Provenza, AIA, P.E., LEED AP BD+C, Jeffrey Smilow, P.E., F.ASCE, Yujia Zhai, P.E., and Motaz Elfahal, Ph.D., P.E.

T

o Rebuild or Reposition? That is the fundamental question every developer must address when acquiring a site with existing conditions. In New York City, a place known for its ephemeral urban fabric and innovative high-rise buildings, large developments often lean towards a tabula rasa (clean slate) for ease of construction and maximum flexibility. Cove Property Group, however, had other plans when they acquired a drab eight-story commercial building on 34th St and 9th Ave in Manhattan. The existing 1960s-era cast-in-place concrete building would receive seventeen additional floors, encompassing 300,000 square feet, in the form of a sleek steel office tower.

When its transformation is complete, Hudson Commons will be a 26-floor, LEED Platinum Class A property accommodating 700,000 square feet of rentable office space (Figure 1).

Hudson Commons was conceived by Cove Property Group. The architect of this visionary renovation and addition is Kohn Pederson Fox Associates (KPF) with WSP serving as the engineer of record. Mueser Rutledge Consulting Engineers (MRCE) served as the geotechnical consultant. The construction manager is Pavarini McGovern (PMG).

Project Description Hudson Commons is situated in the heart of Manhattan’s west side.

The area has seen an expansive transformation in recent years, most notably the 14-acre Hudson Yards megaproject just to the west. As a direct neighbor of Penn Station to the east, the site is tightly woven into the urban fabric and infrastructure of New York City.

The existing 423,000 square-foot cast-in-place structure was initially designed as a warehouse and built in 1962. The structure is comprised of two-way concrete slabs on a 24- by 28-foot grid with drop panels, “mushroom” capitals, and a masonry core providing lateral stability. The low, massive building is representative of the period. Early site investigations showed that the robust structure was in excellent structural shape.

The expressive vertical expansion adds 17 floors of steel construction rising to 421 feet, bringing the total rentable area to 700,000 square feet. The addition takes the form of a sleek modern office tower inherently amalgamated to the bold Hudson Yards development rising just beyond. The subtle renovation of the original building, which includes a new wrap-around brick façade and curtain wall, keeps the project grounded in the context of the neighborhood and its 1960s roots.

Accomplishing the vision developed by Cove and KPF required WSP to face several unique challenges which would inspire highly innovative structural solutions. Indeed, the existing cast-in-place columns and footings required sizeable retrofits for the gravity loads of the new tower above, and the existing roof slab required extensive retrofitting to accommodate a landscaped park. The most invasive feature, however, was the addition of a new reinforced concrete core linking existing and new construction to provide lateral stability for the new taller building. Adding to the complexity of the upgrades was the combined decision of the client and the CM team for a shoringfree demolition of a 125- by 25-foot area throughout the existing building to accommodate the new core.

Foundation System The geotechnical composition of the site and the existing foundation elements presented an interesting engineering challenge. While the existing structure was bearing on the good-quality substrate typical of Midtown Manhattan, the bearing capacity ranged from 20 to 40 ton/ft2, and there was a steep drop off through the site. Furthermore, the constraints of working within the confines of an existing structure were immediately evident, particularly for the use of deep foundation elements and the associated equipment.

Figure 1. Before and after renderings of the Hudson Commons renovation.

STRUCTURE magazine 38 Courtesy of Neoscape, Inc. 2017.

The new reinforced concrete core is supconcrete. Also, WSP provided 3-D laser scanported by a new 48- to 72-inch-thick mat ning services for the entire structure which foundation bearing directly on sound bedrock yielded an accurate representation of as-built (Figure 2). With the core walls in-line with column dimensions and locations, the latter existing columns, consideration of existing being critical to tie in the tower grid above. To column foundations added another layer of minimize any potential compatibility effects, complexity. While some column foundations concrete strength for the retrofitting jackets were narrow piers reaching the bedrock, a matched the one determined through the few columns were supported by larger pile coring campaign (approximately 5,000 psi). caps. The latter were treated as breaks in the Continuity of reinforcement was critical mat foundation with cold joints only. The to maintaining a consistent load path. GPR small footprint of the new core translated scanning was performed at each column to large overturning moments which were allowing WSP to map and coordinate locaaddressed by providing 45 600-kip anchors tions for holes to be drilled for reinforcement socketed 45 feet into rock. MRCE specito pass through the existing slabs. Large diamfied 450-ton micropiles socketed 15 feet into eter (#14 bars) and high-strength (Gr 75) sound bedrock to achieve the required load reinforcement were utilized to maintain demand. Three types of foundation retrofits jacket thicknesses under 12 inches, resultwere developed: ing in 60-inch-maximum-diameter columns.

1) Piers-to-rock encapsulating and tied Column capitals were removed to achieve the Figure 2. Existing foundation and in-progress into existing piers-to-rock, desired reinforcement continuity; however, 2) New caisson caps articulating existing foundation mat for shear wall core. they were rebuilt during the cast operation piers-to-rock, and to maintain the original aesthetic (Figure 3).

3) Enlarged caisson caps articulating existing pile caps.

The forming and casting of circular columns in the building’s constrained environment was a costly and troublesome prospect. Shotcrete was used for columns and capitals to circumvent this difficulty.

Gravity System Concrete was placed and compacted/consolidated at the same time due Originally designed as a moderately-loaded warehouse, the existing to the force with which the shotcrete is sprayed. A skilled technician structure is inherently robust. The reprogrammed office building affords hand trowels the last layer, leaving the final product indistinguishable a load “credit” from the reduced demand. Even with this credit, there from traditional methods. Typically used to line tunnels and swimming was insufficient capacity to accommodate 17 additional floors. Large pools, this application by the construction team proved invaluable and spans (up to 48 feet) in the office tower, to achieve expansive column-free was a genuinely innovative and unique feature of Hudson Commons. areas, amplified the demands at the base of the building where more load WSP faced another interesting challenge in the conversion of the goes to fewer columns. Conversely, a smaller number of columns had existing roof to a lush landscaped amenity area, which is one of the the benefit of an overall reduction in the reinforcing steel for the project. numerous green spaces throughout the building (Figure 4). The existThe solution implemented by WSP was the retrofitting of existing ing structure had limited load capacity as it was designed initially as an concrete columns employing new reinforced concrete “jackets.” Before unoccupied roof. The first solution involved a layer of CFRP under the arriving at this solution, and as with any project involving existing slab with a new concrete topping slab. As the landscape design evolved structures, the first task was the assessment of existing conditions to include up to 4 feet of soil in some locations, a critical threshold was and a study of available construction documents. Although some reached making the CFRP-based solution unfeasible (per the provisions original drawings were available, core samples were extracted from of ACI Committee 440 in the Guide for the Design and Construction various locations to determine the in-situ compressive strength of of Externally Bonded FRP Systems for Strengthening Concrete Structures).

WSP worked closely with PMG to determine the most cost-effective approach, and the final structural solution was a secondary support system of steel beams installed under the existing slab in the green areas. New steel members were designed as non-composite sections to eliminate the need to perforate the roof for stud installation. Clips were installed along the length of the beams to prevent lateral-torsional buckling (Figure 5).

Lateral System

Figure 3. Column jacket before and after the casting operation.

Hudson Commons required a full upgrade of its lateral load-carrying system to provide stability of the existing structure and the new tower above. WSP worked closely with KPF, whose architectural design included a new circulation and mechanical core eccentrically placed along the north side of the property to maximize the rentable area.

One of the most notable features of the Hudson Commons core, however, is its prominence in the architectural expression as it rises above the existing building. The new spine of the building reads as such, using exposed architectural concrete to celebrate the material in a tribute to the historic architecture of the neighborhood. continued on next page

N O V E M B E R 2 019

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The two main challenges of the new core system were constructability and the desire by Cove and PMG for a shoring-free demolition for the new core (Figure 7), given that shoring systems are costly and may stifle construction progress. The unique solution implemented by WSP was to reinforce the existing concrete slab with steel members around the perimeter of the area to be demolished. Steel members were installed above and below the slab following the bending moment demand.

Top steel members were removed after casting the core walls. Steel members below the slab were fitted with studs to trigger composite action and remained as a permanent bracket connecting the new core walls with the existing slab. This innovative solution resulted in significant savings in terms of both cost and schedule.

A Vertical Expansion Showcase

Figure 4. Rendering of the green amenity space on the roof of the existing building.

Courtesy of Neoscape, Inc. 2017.

The new reinforced concrete core runs from foundation to the top of the building and is comprised of 10,000-psi concrete shear walls ranging from 12 to 24 inches in thickness (Figure 6). To counteract the torsional effects of the eccentric core, WSP envisioned a box-like configuration wrapping the entire mechanical and circulation program.

In this closed-box system, the core is placed along existing column lines, and the existing columns create breaks in the shear walls analyzed by considering individual piers at the base building. While this might not be ideal from a structural perspective, the benefit of this approach was the absence of link beams in the base building, which allowed maximum flexibility with regards to routing services out of the core. Above the existing roof, the walls are connected through reinforced concrete link beams to provide adequate lateral stiffness. Three-dimensional finite element analysis software was used to model both the existing and new structure allowing for an optimized and efficient structural design.

Figure 5. The underside of roof slab reinforced with additional non-composite steel beams.

40 STRUCTURE magazine

Hudson Commons presented an interesting challenge. Shotcrete column encasements and retrofitting of various foundation elements allowed the addition of 17 floors and about 300,000 square feet of rentable area to the existing structure. Strengthening of the existing roof to accommodate its conversion to a lush amenity space is a standout. KPF’s design celebrates this essential element of the structure by leaving the new spine exposed as it reaches skyward from the base. Careful attention to constructability and sequencing contributed significantly to the project’s success.

Hudson Commons demonstrates unique and innovative solutions to overcome the limitations of adaptive reuse and showcases the possibilities of large scale vertical expansion. With developers and cities alike striving towards more sustainable solutions to expansion, the relevance of such projects is rapidly accelerating. Hudson Commons topped out in late 2018 and was scheduled to be tenant-ready by the end of summer 2019.■ All authors are with WSP. Joseph Provenza is an Associate and the Project Manager.

Jeffrey Smilow is Executive Vice President, USA Director of Building Structures, and Principal-in-Charge of the project.

Yujia Zhai is Vice President of Building Structures and the Project Director.

Motaz Elfahal is Structural Analysis Manager and Vice President of Building Structures.

Figure 6. Reinforced concrete core emerging above the roof slab of the existing building.

Figure 7. Shoring-free slab demolition for the core with temporary steel above the slab and permanent steel below the slab.

structural SUSTAINABILITY Resilience: A Rallying Cry We Can Amplify

By Kate Stillwell

R

esilience may be the phrase of the decade, but it is not a new concept. Structural engineers have been building

resilience all along; it is only now that others are catching on.

And, as structural engineers, there are tangible steps we can take to amplify the resilience we build.

Consider the broader meaning of resilience: the ability of a person or system to adapt to shock and return to a “new normal.”

Figure 1. Sand Palace Mexico Beach, Florida.

In this context, structural engineers need to ask: is structural design truly resilient, i.e., does it achieve its performance objectives, if related elements of resilience are lacking? Most engineers think only about the building. However, a building is only one part of the physical infrastructure, and the physical infrastructure is only one part of a city and community.

Some frameworks for thinking about resilience have a dizzying array of “spokes.” As a simpler alternative, consider the metaphor of stability: resilience as a three-legged stool. Resilient structural design can only serve its intended purpose if the other legs of the stool are also present. Are they?

The three legs are physical resilience (including safe buildings, lifelines, data), social resilience (including neighborhood cohesion, effective governance, NGOs, and many others), and financial resilience (including public aid, insurance, banks).

After the shock of a natural disaster, what good are safe buildings if no one stays to live in them?

The classic case in point: Hurricane Katrina in 2005. Fully 40% of the residents of New Orleans left and never returned. The population ticked back up but was mostly comprised of newcomers. And now, a mere 14 years later, New Orleans suffered another debilitating flood.

The last thing structural engineers should want is for their building to be “resilient in a vacuum,” i.e., functional but abandoned, whether for lack of occupants, finances, infrastructure, or political will (Figure 1).

When structural engineers understand and incorporate these other, interrelated parts of resilience, they increase the chances that their designs will achieve true resilience. It will help prevent their good work designing reliability, predictability, redundancy, and reparability from going to waste.

However, how do structural engineers incorporate inter-disciplinary notions of resilience into their design? It will vary across context, project, physical setting, and ownership, but the intent of this article is to provide food for thought.

be next. What has become abundantly clear is the lack of redundancy in our social and economic systems.

Vulnerabilities exist across all dimensions of resilience, including infrastructure/lifelines, post-event governance, and social connectedness. Making this last point by counter-example, the research of Daniel Aldrich at Northeastern University convincingly shows that communities with high degrees of social connectedness have demonstrably better disaster outcomes – not only survival and displacement rates but also the speed of recovery in the medium- to long-term. And “social connectedness” extends to electronic connectedness. Social media as resilience-builder? Heck, yes!

However, perhaps most fragile is our financial structure. Even a cursory glance at post-disaster financial systems reveals a staggering lack of savings at both macro and micro scales.

At the federal level, FEMA continues to provide post-disaster Individual Assistance grants, but the public is becoming more and more pessimistic about the timeliness and availability of federal relief.

Likewise, FEMA messaging itself has shifted to downward-manage public expectations on grant amounts.

At the municipal and state levels, public entities must constantly balance competing priorities. It might win votes in the short-term to use limited resources to solve here-and-now problems, but this puts a strain on the number of resources available for emergency reserves.

Worst of all is the systematic lack of savings at the individual level.

Annual surveys by Bankrate repeatedly show that a staggering majority of Americans lack even $1,000 in savings. What this means is that the unanticipated expenses of a natural disaster – even just the cost of evacuation – could tip a family into a spiral of debt.

The leverage of financial resilience cannot be understated. Case studies from two different historical and cultural contexts make this point.

Redundancy: Notably Lacking

Figure 2 is a photo of the 1906 San Francisco earthquake showing a group of people on Potrero Hill, smoke billowing in the background.

Their city is in flames, yet they are smiling, as if undaunted. They possibly foresaw what would happen over the next decade: massive

We have all seen the social and economic disruption from extreme disasters, and it is frightening to imagine that your home town could 42 STRUCTURE magazine

Recovery is Driven by Money: Case Studies

massive public and private investment, $50 million at the time. In business at the “top of their list” for post-disaster work. This way, today’s dollars, considering the population in 1906, this amounts to they limit the degree and expense of follow-on damage such as $2,500 per capita – which is astounding because it is 5 to 10 times mold or sprinkler leakage. the per-capita post-disaster disbursements that are typical in recent The Napa earthquake occurred early on a Sunday morning. One decades. This allowed San Francisco to bounce back so definitively three-story building in the city center, used as an administrative center that it hosted the 1915 Pan-Pacific Expo and established itself as for processing legal documents, was unoccupied at the time. From an international destination. the exterior, there was no visible damage. Therefore, no one entered INFO SPECS Something similar happened in the decade after the M7.7 2001 the building until Monday morning, more than 24 hours later. By FileName: Structure_July_Bridge Solutions due PagetoSize: 5w" x 7.5h" bleed head Bhuj (India) earthquake. It was a tragic disaster for thousands of 19-1670_Ad_1/2Island then, extensive flooding hadRepair occurred a single sprinkler PR#: N/A Number of Pages: 1 people, but at the macro level, it was a financial success story.Job#: The19-1670 that had sheared off. Many of the legal documents were permanently Artist: Morra Email: damaged. gmorra@mapei.com Bleed: Yes Amount: .125" state and national government into Georgina and irreplaceably 1 1 4 4quickly E . N e w pinvested o r t C e n t $2 e r Dbillion r.

Deerfield Beach, FL 33442 Date: June 7, 2019 10:29 AM Colors: CMYK Process, 4/0 the rebuild. This had the flywheel effect of attracting another $10 The point is not that it is necessary to strengthen the building so N O T E : C O L O R S V I E W E D O N S C R E E N A R E I N T E N D E D F O R V I S U A L R E F E R E N C E O N L Y A N D M A Y N O T M A T C H T H E F I N A L P R I N T E D P R O D U C T. be billion or more from the private market, enough to create momen- that none of the sprinkler heads will shear off; there will always tum for a remarkable economic boom.

Over the following decade, the state of Gujarat experienced 10% GDP growth, and the employment of women doubled.

Some have gone so far as to call this the “Gujarat miracle.”

Extending Our Reach: Contingency-Planning

Carroll Avenue Bridge Takoma Park, MD

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Disasters cause unanticipated consequences unrelated to damage, which have real costs and affect recovery, and structural engineers have the know-how to extend resilience-building beyond just construction documents. Here are two examples from the M6.0 Napa earthquake in 2014.

This first example demonstrates how the client can gain critical information for contingency-planning if the structural engineer performs an assessment of the immediate vicinity.

Velo Pizza is a thriving local business in Napa in a historic masonry building.

The owners had done the right thing and had retrofitted their building. When the 2014 M6.0 earthquake struck, the employees and the customers all stayed safe, and there was basically no damage.

Initially, they had a green tag, “safe to occupy.” Then a red tag was added below the green tag – Unsafe. What was that all about? The building next door, also an unreinforced masonry building, was not retrofitted, and there was the dangerous possibility that, in an aftershock, bricks from next door would fall through Velo’s roof and hurt someone. At no fault of their own, Velo had to close temporarily and lost revenue. The employees lost income. If Velo knew about this contingency (maybe they did!), they could have made specific plans to mitigate its financial consequences.

The other example illustrates the potential value for a client to engage a repair contractor on retainer, putting their

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surprises you cannot plan for. The point is to make a contingency plan so that someone goes to the building within an hour and turns off the sprinklers, thus limiting the damage.

The author set out to tackle some of these interrelated resilience challenges. In the choice between social versus economic challenges, it was natural to gravitate toward financial, being an engineer and comfortable with numbers. The financial challenge Practical Steps to of resilience is two-fold: not only do Amplify Resilience Americans have an abysmally low Structural engineers are uniquely savings rate, but 9 out of 10 people influential in building resilience in forego non-mandatory insurance for all its forms. We can help clients the most severe disasters like earthbuild social and financial resilience quake and flood, which disrupt life as well as structural resilience. The for whole communities, whether or not Table is only a starting point. When an individual’s property suffers damage. we take tangible steps to help build This led the author to a commitment the interrelated parts of resilience, to build financial resilience for both it will amplify the resilience of our individuals and communities after a structural design. The Table presnatural disaster. Even though not curents actionable ideas for SEs to help rently practicing engineering, there is promote address financial and social still a strong alliance for the author with Figure 2. San Franciscans on Potrero Hill. resilience. the SE community because the mission remains fundamentally the same as the resilience-building motive of structural engineers.

One SE’s Professional Journey One of the best things about being a structural engineer is the gratiThe author became a structural engineer to make the world a better fication of making the world safer and more resilient. And place – to save lives and protect livelihoods. Starting to practice in that gratification only increases when we extend our services 1998, Hurricane Katrina in 2005 presented a professional crisis: Are to build resilience more broadly. Onward!■ safe buildings serving their purpose if no one stays to live in them?

Our social and economic systems are much more fragile than our Kate Stillwell is the Founder and CEO of Jumpstart, and she builds financial buildings. How can we bring the talents of our profession to these resilience through parametric insurance. Kate is SEAONC Past President larger challenges of resilience? What are the best ways for us to bolster and a SEAONC Fellow. She also co-founded the U.S. Resiliency Council other, interrelated systems so that the built environment can more and the GEM Foundation. effectively do the job we are designing it to do?

Table of actionable ideas to promote resilience.

Actionable Ideas

Financial Resilience

Social Resilience

At the building-specific level

• Coordinate our design with the insurance broker to develop a custom policy that is tied to structural performance

• Offer client services to propose standards and incentives for neighboring buildings or community redevelopment to achieve resilience. This is particularly relevant to larger developments.

At the organizational level

• Advise clients on what level of downtime, and therefore time-induced losses, they may experience to assist them in determining the amount of business interruption insurance to buy • Advise clients to hire structural engineers or other professionals “on-call” to stem post-disaster losses (see the example in the article)

• Encourage risk managers to become members of interdisciplinary resilience-building organizations such as EERI or the Earthquake Country Alliance • Offer client services for evaluation of the other aspects of resilience – for example, cost-benefit analyses, probabilistic studies, lifeline interdependency evaluations, etc.

At the individual level

• Encourage clients to add employee benefits that • Employer-sponsored activities such as athletics bolster post-disaster financial stability, such as • Employer-specific groups on social networks, such as Facebook, for the sole use of postsavings plans or insurance policies that pay right disaster communication and coordination away. The availability of funds makes it more likely for employees to come back to work. This is especially important for organizations that provide post-disaster services such as utility districts and hospitals (and structural engineers!)

44 STRUCTURE magazine

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structural REHABILITATION Adaptive Reuse of the Apex Hosiery Company Building Part 1: History of the Philadelphia Demolition Ordinance and the Apex Hosiery Building

By D. Matthew Stuart, P.E., S.E., P.Eng, F.ASCE, F.SEI, A.NAFE, SECB

T

his four-part series discusses how the collapse of a building during a demolition operation in Philadelphia in 2013, which resulted in several fatalities, led to enactment of a City Ordinance to prevent similar future calamities. As a result of the Ordinance, the author became involved with the structural investigation, review of the Site Safety Demolition Plan, and Demolition Special Inspections associated with the adaptive reuse of the Apex Hosiery Company Building located in Philadelphia.

As a result of the investigation, a unique type of reinforced concrete flat slab construction, the SMI System, was encountered. The author had previously dealt with this type of construction at another building in Philadelphia. The findings of the investigation assisted with the successful completion of both the partial demolition of the existing structure and the success of the adaptive reuse project.

Building Demolition Collapse On June 5, 2013, a building associated with the demolition of a series of adjoining two- and four-story mercantile loft structures collapsed onto the immediately adjacent, one-story Salvation Army Thrift Store building. The thrift store was located at the corner of South 22nd Street and Market Street in Philadelphia and was open and full of shoppers at the time of the collapse. The collapse resulted in the death of six individuals and seriously injured fourteen people.

The unintended collapse was precipitated by an unsupported, fourstory masonry brick wall that was immediately adjacent to the Thrift Store. The unstable condition was created when the demolition contractor removed most of the floor and roof framing, originally connected to the same wall, using an 18-Ton excavator. The aftermath of the collapse can be seen in Figure 1.

As a result of the incident, both the demolition contractor and operator of the excavator were convicted of six counts of involuntary manslaughter and sentenced to prison. Six months after the incident, OSHA also levied fines against the demolition contractor’s and excavator’s companies. Also, the project developer, the architect who had been hired to monitor the demolition, Figure 2. Apex Hosiery Company Building and the Salvation Army were located in Philadelphia – prior to renovation.

46 STRUCTURE magazine

Figure 1. The aftermath of a June 5, 2013, building collapse associated with demolition of a series of adjoining two- and four-story mercantile loft structures onto the immediately adjacent, one-story Salvation Army Thrift Store building in Philadelphia. Courtesy of Lindsay Lazarski, WHYY.

found to be responsible for the fatalities and injuries by a civil court jury. The ruling resulted in a total settlement of $227 million for the individuals that were killed or injured in the incident.

City of Philadelphia Demolition Ordinance At the time of the collapse, the City of Philadelphia did not require demolition contractors to document their qualifications. However, as a result of the incident, the City announced two days after the collapse that new demolition rules and standards would be enacted to prevent similar tragedies in the future.

The new City Ordinance documented several new demolition permitting requirements, including: 1) Post a notice of the demolition of a structure and distribute notifications to properties adjacent to and near the building to be demolished.

2) Site plan.

3) Demolition schedule.

4) Special Inspections.

5) The submission of a Site Safety Demolition Plan or “engineering survey” as required by OSHA that includes: a) Details of the type of construction and condition of the structure to be demolished. b) Inspection details of the structural conditions of the adjoining properties. c) Description of the means and methods of protecting adjacent structures. d) Description of the method of demolition. e) Details of potential hazards. f ) Confirmation of the presence of underground utilities. g) Description of safety and environmental issues.

Continuous demolition Special Inspections were also required by the Ordinance, and must also be overseen by a licensed structural professional engineer for the following conditions:

Figure 3. The 6-story structure was constructed as a reinforced concrete, flat slab supported by round and rectangular columns with column capitals and drop panels.

1) Demolition of a building in excess of three stories or 40 feet in height.

2) Where the use of mechanized demolition as a part of the Site Safety Demolition Plan, or SSDP, is approved by a licensed structural engineer.

Site Safety Demolition Plan and Special Inspection Project

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As a result of the demolition Ordinance, the author became involved in a number of demolition projects.

The services provided to clients for demolition projects included the development of demolition bid documents, Figure 4. Two-way reinforcing was confirmed to be orthogonal and parallel to which are not required by the Ordinance, the engineering the main column grids and did not include any diagonal 4-way reinforcing. review of Site Safety Demolition Plans (SSDP) developed by demolition contractors, and Special Inspections that are performed by a separate inspection and testing division of Apex Hosiery Company Building History the author’s firm, Pennoni. One of the most interesting demolition projects that the author has been involved with was the adaptive reuse The original building was designed by Architect Frederick Muhlenberg of the Apex Hosiery Company Building located in Philadelphia, for use by the Apex Hosiery Company and built in the 1920s; the shown in Figure 2. building was in use until April 1954 when the factory was closed.

The renovation of the existing, six-story reinforced concrete manuFollowing a series of ownership changes, the School District of facturing building involved the demolition of the Penthouse, roof, and Philadelphia purchased the building in 1967, and the factory floors 6th and 5th floors, leaving a three-story structure that was to be used were converted into classrooms for a middle school. In June 1984, as affordable rental housing. Structural engineering services for the project involved both pre-demolition and post-demolition condition assessments of the structure and façade, and Special Inspections during the demolition phase. The pre-demolition survey included Demos at www.struware.com the installation of several crack monitors at selected locations within Wind, Seismic, Snow, etc. Struware’s Code Search program calculates these and the portions of the building that were to remain for the purpose other loadings for all codes based on the IBC or ASCE7 in just minutes (see online of monitoring movement of the structure during the demolition video). Also calculates wind loads on rooftop equipment, signs, walls, chimneys, phase. The pre-demolition effort also involved a peer review of the trussed towers, tanks and more. ($250.00).

SSDP that had already been approved by another engineering firm.

CMU or Tilt-up Concrete Walls Analyze solid walls for out of plane loading and In addition, the author completed a gravity load capacity analysis panel legs next to or between openings by automatically calculating loads to the wall leg from vertical and horizontal loads at the opening. ($75.00 ea) of the remaining structure to confirm the feasibility of the proposed adaptive reuse of the building. Because there were no existing Floor Vibration Program to analyze floors with steel beams and/or steel joist.

Compare up to 4 systems side by side ($75.00). structural drawings for the building, the load-carrying capacity was determined via small, exploratory demolished openings in Concrete beam/slab Program to provide bending, shear and/or torsional reinforcing.

Quick and easy to use ($45.00). the existing concrete slab, used to observe and document the size, spacing, and concrete cover of the internal reinforcing.

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the school was renamed Roberto Clemente Middle School and remained in use until the mid-1990s when a new Clemente school building was constructed elsewhere in the city. The building was subsequently used for storage but became deteriorated and was abandoned in 2007.

Description of Structure

Figure 5. Based on observations, the reinforcing was confirmed to be the SMI, or Smulski Method system, which involved the use of smooth, round concentric rings, or hoops, of small-diameter steel bars. Courtesy of ACI Journal Proceedings, 1918.

A Test of the SMI System of Flat Slab by Edward Smulski

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Part 2 of this series will provide more details on the SMI system and peer review of the site safety demolition plan.

ZERO LOOSENESS Matthew Stuart is the Senior Structural Engineer at Pennoni Associates Inc. in Philadelphia, PA. (mstuart@pennoni.com)

48 STRUCTURE magazine

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The footprint of the building, which somewhat resembled the shape of the letter F, occupied most of the triangular block bounded by North 5th Street, Rising Sun Avenue, and West Luzerne Street. The 6-story structure was constructed as a reinforced concrete, flat slab supported by round and rectangular columns with column capitals and drop panels, as shown in Figure 3, page 47. Laboratory material testing of the existing reinforcing samples and in situ non-destructive evaluation of the existing concrete compressive strength were performed along with field measurements of the critical structural components of a typical framed level. The average in situ concrete compressive strength of 6,000 psi was established via both a Schmidt Impact Hammer and a CAPO-TEST pullout device.

Based on observations at several exploratory openings in the south end of the building, the two-way reinforcing was confirmed to be orthogonal and parallel to the main column grids and did not include any diagonal 4-way reinforcing (Figure 4, page 47). The top reinforcing bars were also “trussed,” in other words bent down, towards the bottom of the slab near the edge of the drop panels and thus became the bottom reinforcing, a common method of rebar placement during the era in which the building was constructed.

Based on observations at additional exploratory openings in the north end of the building, the reinforcing was confirmed to be the SMI or Smulski Method system, which involved the use of smooth, round concentric rings, or hoops, of small-diameter steel bars as illustrated in Figure 5. The north and south sections of the main rectangular building footprint were separated by an expansion joint; therefore, it was evident that the separate north and south portions of the building had been built using two distinctly different methods of two-way flat slab construction that were available during the era the facility was constructed.

Why this situation occurred during the construction of the building was unclear, particularly in light of a 1922 article from a textile industry publication that indicated a single design/ build contractor, Beling-Bush Company, Inc., was awarded the project. However, a review of a historic Sanborn Fire Insurance Map of the property indicates that the north and south sections of the building were constructed at different times. The northern half appears to have been completed first in 1923

by Beling-Bush Company, Inc., while the southern half was completed in 1925 presumably by another contractor. Also, per the same map, the eastern wings of the building associated with the southern half of the facility were completed even later, in 1929.■

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professional ISSUES Upfront and In Need Affordable Housing Explained

By Dallas Erwin and Kate Peterson

A

ffordable housing is in the news more than ever before.

As rising rents and harrowing rates of homelessness echo

across the country, housing advocates are relieved to see the spotlight finally shine on the need for this essential community resource, but their relief is shortlived. All this attention is the result of millions of families searching for a stable place to call home. The National Low Income Housing Coalition (NLIHC)

833 Bryant rendering.

estimates that there’s a shortage of 7.2 million homes. Innovative partnerships are slowly creating positive change. To build more and better housing for the people that need it most, resourceful engineers are necessary. Affordable housing building trends offer a glimpse into the sweeping social change affecting neighborhoods and how engineers can make a difference.

From an engineer’s perspective, affordable housing and market-rate developments are similar in many ways. What is different is the funding The phrase “affordable housing” isn’t always understood uniformly and, consequently, the planning. All well-executed real estate developoutside of the industry – essentially it offers subsidized homes for ments have concise planning, but affordable housing needs the details low-income individuals to help free them from rent burden (more earlier than what is commonly expected with market-rate properties. than 30% of income going to rent), so they have more resources to Mercy Housing’s seasoned real estate developer, Kuhl Brown, offers spend on other essentials like food, healthcare, and education. insight into the affordable housing industry and what that means for the Mercy Housing is an affordable housing nonprofit; with a presence engineering aspect of planning: “We often need engineering design input in 41 states, they have over 37-years’ experience serving low-income and insight early, requiring higher concept detail upfront. Affordable families, veterans, seniors, and people with special needs. Mercy Housing housing funding is typically competitive, and pre-development is a partners with communities to make long-term commitments, resulting huge component of being successful.” The subsidies Kuhl references in positive, measurable outcomes for residents and neighborhoods. are the Low-Income Housing Tax Credits (LIHTC). Pronounced colloquially as ‘lie-tech,’ it is not a buzz word, but rather the lifeblood of affordable housing. Created in 1986 under the Reagan Administration, this vital funding source Professional Master in Structural Design of Tall Buildings raises private equity for affordable housing through the allocation of federal tax Dreaming of getting a credits going toward the rehabilitation and professional master’s degree construction of below-market-rate housing but can’t leave your job? for low-income tenants. LIHTC funding is excruciatingly competitive, while compliEarn a professional master’s degree in structural design of tall ance is held to the highest standard and buildings from an internationally administered by state housing finance agenrecognized institution through cies. Deadlines are strict; you can typically blended learning only apply for LIHTC funding twice a year, [online + in-class] but each state is different. Kuhl confirms approach that “construction type has a huge impact For more info because land and sites are scarce and we solutions@ait.ac.th are competing for the same land and labor Apply now! +(662) 524 6388 costs that market-rate developers can fund solutions.ait.ac.th/pmtb through private equity.”

Offered by There are several takeaways for the strucCivil and Infrastructure Engineering Department, tural engineer. First, the project will be School of Engineering and Technology, Asian Institute of Technology (AIT), Thailand front-loaded more than a typical project, meaning more fee will be needed in the

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Affordable Housing

PMTB

50 STRUCTURE magazine

planning and schematic design phases. Also, the level of detail required Ready to Roll Up Your Sleeves? early will be greater than normal. Many structural engineers are only used to selecting the structural system and roughing out typical Tightened budgets and deadlines make 3-D modeling increasingly member sizes during schematics but, for affordable housing projects, popular to reduce planning errors. Modular construction is another the architectural design is very far advanced, so the structural design trend that is increasingly appealing in the affordable housing scene. needs to be too. Beam and column sizes and wall thicknesses need to Structural engineers with experience and know-how with evolving be determined accurately for both coordination and accurate pricing. technologies focused on cost-effective quality construction (low mainLIHTC geographic allocation tenance), and those that have the can be enhanced through a 30% They [firms with affordable housing experience] are communication skills to engage basis boost that is decided by the familiar with our unique requirements; these architects with the developer, architect, and U.S. Department of Housing and and engineers know our design priorities and often how we choose contractor in project development Urban Development (HUD). and problem-solving, have a leg who to go with – experience and trust. It is particularly appealing HUD’s Qualified Census Tract up. Kuhl notes that “We are always (QCT) is the mapping system when all architects and engineers are under one firm – again, this asking, is there a more efficient prothat annually chooses tracts to be is friendly to time and cost. Because of our financing structures, duction possibility offsite? Some of included as a QCT based on the we are trying to be more efficient with less money. Especially in these offsite construction methods tract’s income. This often becomes competitive markets, we need to maximize scale and units on can cut down on construction time essential in determining the via- smaller urban sites. The same problems that are common by six to eight months. Efficient bility of where LIHTC funding structural and civil engineering is can go. The decision ultimately for market-rate can pop up with affordable housing.” essential when it comes to doing

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changes the substantial up-front more with less.” ~ Kuhl Brown, Mercy Housing planning for engineers due to each When Kuhl is asked what engisite locations’ unique geological and zoning concerns. QCTs are com- neers can do if they are interested in affordable housing, he recommends monly found in lower-income and middle-income areas and often in to simply “Get out and tour some; most developers love showing off what higher-density urban areas. they have built!” Nonprofits like Mercy Housing do not just build homes; Additionally, state and city ordinances require lengthier and more they build a sense of community. Creative collaboration is a theme of detailed applications for affordable housing. “We cannot move for- not only affordable housing construction but the entire industry as well. ward with construction until city and state applications are awarded, Housing is a complex, multifaceted issue that touches so many aspects plus capital campaigns must be in place prior as well. We are held of society, and partnerships are vital. The affordable housing industry to an even higher standard because our funding provides tax credits; continues to measure and quantify the far-reaching benefits certain states require amenity packages that are at or above market of stable homes. From engineers to civic leaders and even rate developments, depending on the market.” healthcare professionals, the message is clear, home is hope.■ During the initial planning, developers first look for need – does this community truly need below-market-rate housing? There is a myriad of Dallas Erwin is Mercy Housing’s Content Manager. (derwin@mercyhousing.org) economic and sociopolitical factors that play into this. Secondly, they Kate Peterson is the Senior Vice President of Marketing and think about opportunity – zoning and availability factors must fall into Communications for Mercy Housing. (kpeterson@mercyhousing.org) place. Thirdly, perhaps the most challenging, funding – LIHTC is part of this equation and notably the country’s largest affordable housing resource, but it is not the only available opportunity.

Local and other soft funding sources can be critical for success. There are no quick answers to these questions.

The value of the LIHTC credits dropped recently with the federal tax reform that lowered corporation and business tax rates and thus their need for credits. Additional headwinds are construction costs, which THE are climbing nationally but also somewhat market dependent. Kuhl points to resourcefulness and creativity as the FOR MECHANICAL AND ADHESIVE ANCHORS paths forward; “We are always balancing cost and need with even small things like IN THE INDUSTRY parking and other parts of the development that may be seemingly simple, yet complex from a development and zoning or entitlement perspective.” Affordable housing developers often use engineers WWW.ANCHORS.DEWALT.COM and firms that have previous experience with below-market-rate housing for pracCopyright ©2019 D E WALT ticality and cost saving purposes.

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NCSEA NCSEA News

National Council of Structural Engineers Associations

2019 NCSEA Special Awards Honorees

The Special Awards honor individuals who have provided outstanding service and commitment to the association and to the structural engineering field. These prestigious awards will be presented at the NCSEA Awards Celebration taking place at the Structural Engineering Summit in Anaheim, CA, on November 14, 2019. Visit www.ncsea.com to learn more about the Special Awards and about this year's recipients.

Congratulations to the 2019 Special Awards Honorees!

NCSEA Service Award This award is presented to an individual who has worked for the betterment of NCSEA to a degree that is beyond the norm of volunteerism. It is given to someone who has made a clear and indisputable contribution to the organization and the profession.

Ben Nelson, P.E., is Structural Division Manager and Chairman of the Board for Martin/Martin Consulting Engineers, based in Lakewood, Colorado. He has practiced structural engineering for over 35 years, all with the same firm. He served on the Board of the Structural Engineers Association of Colorado (SEAC) for 5 years and was President in 1999. He was SEAC’s delegate to NCSEA from 2002-2010 and was elected to the NCSEA Board of Directors in 2007, serving 7 years, including NCSEA President in 2012-2013.

While NCSEA President, Mr. Nelson founded the initial Young Member Group (YMG) which evolved into the YMG Support Committee as well as the YMG scholarship program to encourage greater participation at the NCSEA Annual Conference, later the NCSEA Summit. He is most proud of the growth of YMGs throughout nearly all of NCSEA’s Member Organizations and their substantive impact to the future of NCSEA and the structural engineering profession.

Mr. Nelson also established NCSEA’s Susan Frey Educator Award in 2014 and has served on NCSEA’s Awards Committee since 2013. He has presented numerous talks and sessions to structural engineers throughout the country. In his 17 years with NCSEA, he also actively served on many NCSEA committees including Advocacy, Winter Institute, Structural Engineering Summit, Continuing Education, and Member Organization Liaison/Communications.

Robert Cornforth Award This award is presented to an individual for exceptional dedication and exemplary service to an NCSEA Member Organization as well as to the structural engineering profession.

Thomas A. DiBlasi, P.E., SECB, has been a practicing engineer for over 34 years and is a licensed Professional Engineer in 14 states. Over the past 34 years, he has moved the profession forward by being an active member of many boards, associations, and committees, and also by encouraging staff and future generations of structural engineers to participate in professional learning opportunities and to get involved.

Mr. DiBlasi is the Principal/President of DiBlasi Associates. The success of DiBlasi Associates is due to DiBlasi's own dedication to the field as well as his mentoring and support of his small, yet impressive staff of only four.

He has been involved with the Structural Engineers Coalition of ACEC/CT since its inception in the 1980’s. He carried over that support to NCSEA, where he represented Connecticut as their delegate, he served as President of the Board of Directors in 2011-2012, and where he currently sits as Chair of the Code Advisory Committee.

Mr. DiBlasi has made important contributions to the field at both the state and national level which is highlighted though his tireless work on committees that focus on a variety of aspects of the field from professionalism to code writing, to supporting future engineers.

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News from the National Council of Structural Engineers Associations Susan M. Frey NCSEA Educator Award This award, established to honor the memory of Sue Frey, one of NCSEAâ&#x20AC;&#x2122;s finest educators, is presented to an individual who has a genuine interest in, and extraordinary talent for, effective instruction for practicing structural engineers.

Dr. S. K. Ghosh heads the consulting practice, S. K. Ghosh Associates LLC, Palatine, Illinois, now a subsidiary of the International Code Council. Dr. Ghosh is active on many national technical committees, is an Honorary Member of ACI, and is a Fellow of ASCE, SEI, and PCI. He is a member of ACI Committee 318, Standard Building Code, and the ASCE 7 Standard Committee (Minimum Design Loads for Buildings and Other Structures). He is a former member of the Board of Directors of ACI, EERI (Earthquake Engineering Research Institute), and BSSC (Building Seismic Safety Council). He is a member of the Board of Governors of ASCEâ&#x20AC;&#x2122;s Structural Engineering Institute.

Dr. Ghosh has influenced seismic design provisions in the United States for many years. In addition to authoring many publications in the area of structural design, Dr. Ghosh has investigated and reported on structural performance in most recent earthquakes.

James Delahay Award This award is presented at the recommendation of the NCSEA Code Advisory Committee to recognize outstanding individual contributions towards the development of building codes and standards. It is given in the spirit of its namesake, a person who made a long and lasting contribution to the code development process.

Kelly E. Cobeen, S.E., joined WJE in 2008 with twenty-three years of experience in structural design, working in a wide range of project types, sizes, and construction materials. She has a special interest in seismic resistance of light-frame construction, applicable to new construction and seismic upgrade of existing buildings.

Ms. Cobeen has been involved in numerous code development, research, and educational activities.

Her code development activities include involvement in the NEHRP Recommended Provisions for Seismic Regulations for New Buildings, as well as the International Building Code and International Residential Code development. Her educational activities include coauthoring the Design of Wood Structures textbook, teaching wood design at University of California, Berkeley, and teaching seminars for professional organizations.

In addition to light-frame construction, Ms. Cobeen has extensive experience in design, evaluation, and seismic upgrade of a wide range of building types, including concrete shear wall and frame buildings, steel braced and moment frame buildings, masonry buildings, and masonry infill buildings.

NCSEA Webinars

Register by visiting www.ncsea.com.

November 7, 2019

December 5, 2019

Jim Vogt, P.E.

William L. Coulbourne, P.E., SECB, F. SEI, F.ASCE

November 19, 2019

December 10, 2019

Jeffrey Hill, P.E.

Dr. Scott Breneman

Permanent Bracing for Metal Plate Connected Wood Trusses

Ground Improvement for Structural Engineers

ASCE 7-16 Determining Component and Cladding Wind Pressures for Roofs

Mass Timber Structural Floor & Roof Design

Courses award 1.5 hours of continuing education after the completion of a quiz. Diamond Review approved in all 50 states.

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SEI Update Learning / Networking STRUCTURAL ENGINEERING INSTITUTE

STRUCTURES CONGRESS 2020

Sponsor/Exhibit to showcase your brand.

St. Louis, Missouri I April 5-8

Registration is open! NEW Group registration discount is available. Check out the program and sessions and plan your schedule.

www.structurescongress.org

Visit the ASCE Bookstore at the NCSEA Summit November 12-15 in Anaheim, CA.

Check out ASCE 7 Online and Hazard Tool demos and enter for a chance to win a 6-month individual subscription to ASCE 7 Online.

Students/Young Professionals

Welcome Joseph Burns to the SEI Futures Fund Board Joseph G. Burns, P.E., S.E., CEng, F.IStructE, F.ASCE, F.IABSE, FAIA, Managing Principal, Thornton Tomasetti, joined the SEI Futures Fund Board on October 1 for a five-year term. With more than 35 years of experience, Joe is a passionate advocate for the deeper integration of architecture and engineering, which he promotes through innovation, collaboration, and leadership. A member of Thornton Tomasetti’s board of directors, his practice is based in Chicago while overseeing the firm’s operations in the Middle East and Brazil.

Joe comments, “I am very excited to join the SEI Futures Fund Board, and engaging in its challenge of supporting the growth and advancement of future generations in the structural engineering profession. Early in my career, I became engaged with the ASCE Committee on Aesthetics in Design. This gave me an opportunity to collaborate with structural engineers beyond my experiences at work, and led to a series of leadership positions within the ASCE Structural Division as chairman of the Committee on Aesthetics in Design, Chair of the SEI Technical Activities Committee on Special Design Issues, and member of other committees like the Tall Building Committee. This certainly had a big impact on my professional development and evolution. I am delighted to be in a position to assist our next generation the way I was supported and mentored as a young engineer.”

SEI Online

Structural Engineering Channel Podcast Check out recent podcasts with SEI leaders on Confidential Reporting on Structural Safety Now in the U.S., Performance-Based Wind Design, and more at https://engineeringmanagementinstitute.org/tsec-podcast.

SEI on Twitter

Follow us: @ASCE_SEI 54 STRUCTURE magazine

SEI on Facebook SEI Standards Follow us: @SEIofASCE

Visit www.asce.org/SEIStandards to: View ASCE 7 development cycle

News of the Structural Engineering Institute of ASCE Membership

From Glenn Bell on Serving as SEI President FY20 Structural Engineering is the greatest profession on the planet. The work is challenging and meaningful, we serve society in critically important ways, our members are of outstanding caliber and integrity, and we have fantastic professional organizations like ASCE/SEI to propel us forward.

My career to date has encompassed 45 years at Simpson Gumpertz & Heger Inc., 24 of them as its CEO and/or Board Chair. The work has been fascinating, has stretched me in directions I never expected, and has offered a secure and comfortable means of living. My colleagues are exceptional individuals.

While I have long been involved in ASCE and SEI, some years ago, I decided that when I gave up my CEO hat and had more time as I transitioned toward retirement, I would give back to this great profession by stepping up my professional leadership. A pivotal event for me was a closing keynote address I delivered at Structures Congress 2012 entitled Developing the Next Generation of Structural Engineers. The theme resonated with many in the audience, and opportunities started to flow over the transom. Within a few years, I found myself on the board of the SEI Futures Fund, was a founding ExCom member of the new SEI Global Activities Division, and joined the SEI Board of Governors. I also was drawn into the Institution of Structural Engineers in the UK, where I currently serve as a Board Trustee. SEI and IStructE have formed a great collaboration; we held our first international structural engineering conference in Dubai at the end of September. An unexpected bonus of these commitments is that I have developed a network of close professional friends around the globe. When the invitation came to stand for the position of SEI President, I did not hesitate.

My goal as SEI President will be to help continue our work to prepare structural engineers and the structural engineering profession for a vibrant and sustainable future. Collectively, we have done great work since the publication of the SEI Vision document in 2013. Most notably, we have made significant advances in adoption of performance-based design, globalization, and collaboration with like-minded professional

organizations. However, there is so much more to be done. We live and work in turbulent times where the pace of change brought on by technological, societal, political, and economic influences is staggering.

While we may find these changes unsettling, I think we live in the most exciting time for the future of structural engineering because society will need highly qualified and creative structural engineers to meet its future challenges. To secure this opportunity, we must simultaneously develop a new breed of structural engineers while elevating our profession to play more impactful roles.

In advancing structural engineers and structural engineering, these are particular topics I am passionate about: • Young Professionals: I am tremendously inspired by the creativity, energy, and brilliance of our youth. The role of we “more mature” of the SEI leaders should be to unleash and enable that youthful talent and ambition.

• Reform of Structural Engineering Education: We have long recognized that, to excel in the future, we need structural engineering leaders that are more creative, communicative, and collaborative. This requires a revolution in SE education.

• Bringing Together Practice, Education, and Research: If we are to have a genuinely innovative, dynamic, and responsive profession where new materials, structural systems, and processes are brought to practice more quickly, we need an integrated relationship between practitioners, teachers, and researchers.

• Collaboration with Like-Minded Organizations: We in SEI cannot accomplish what we need to in a vacuum. The AEC industry is vast and siloed. There is a whole world out there that we must embrace.

I am grateful for the opportunity to serve as your President. In the next year, I am committed to engaging with as many of our members as possible through travel and physical meetings, as well as through all virtual channels available. Please get involved in an SEI Chapter or Committee effort. There is much work to be done and many opportunities. www.asce.org/SEI

Advancing the Profession

Confistructural dential Reporting on Structural system that captures and shares lessons Improve learned from structural safety issues engineering Safety practice which might not otherwise be available to the public. and public safety Access free reports on structural safety and sign up for updates at www.cross-us.org.

Anyone is invited to confidentially submit through learning reports of structural failures, near misses, concerns, and incidents, for anonymous from failures and development of Supplements analysis commentary SEI Standards andby Errata including ASCE 7. See www.asce.org/SEI-Errata. near misses. subject matter experts, and to use the Errata If you would like to submit errata, contact Jon Esslinger at jesslinger@asce.org.

CROSS-US is a confidential reporting

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f Learn more www.cross-us.org | www.asce.org/SEI

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CASE in Point Did you know?

CASE has tools and practice guidelines to help firms 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, keep track of the skills young engineers are learning at each level of experience, or need a sample contract document – CASE has the tools you need!

CASE has several tools available for firms to use to enhance their construction management practices.

CASE #4 – CASE #6 – CASE #7 – CASE #8 – CASE #12 – Commentary C – CASE 962-D – CASE 962-E – CASE 962-F – CASE 962-G – Tool 2-4 Tool 4-3 Tool 9-1 Tool 10-1 Tool 10-2

An Agreement Between Client and Structural Engineer for Special Inspection Services An Agreement Between Client and Structural Engineer for a Structural Condition Assessment An Agreement for Structural Peer Review Services An Agreement Between Client and Structural Engineer for Forensic Engineering (Expert) Services An Agreement Between Structural Engineer of Record (SER) and Contractor for Transfer of Digital Data or Building Informational Model File Commentary on AIA Document A201, General Conditions of the Contract for Construction, 2017 edition A Guideline Addressing Coordination and Completeness of Structural Construction Documents Self-Study Guide for the Performance of Site Visits During Construction A Guideline Addressing the Bidding and Construction Administration Phases for the Structural Engineer Guidelines for Performing Project Specific Peer Reviews on Structural Projects Project Risk Management Plan Sample Correspondence Guidelines A Guideline Addressing Coordination and Completeness of Structural Construction Documents Site Visit Cards Construction Administration Log

CASE Tool 5-1: A Guide to the Practice of Structural Engineering – UPDATED

CASE has updated and released CASE 5-1: A Guide to the Practice of Structural Engineering. This tool is intended to teach structural engineers the business of being a consulting structural engineer and things they may not have learned in college. While the target audience for this tool is the young engineer with 0 to 3 years of experience, it also serves as a useful reminder for engineers of any age or experience. The Guide also contains a test at the end of the document to measure how much was learned and retained. Other sections deal with getting and starting projects, schematic design, design development, construction documents, third party review, contractor selection/project pricing/ delivery methods, construction administration, project accounting and billing, and professional ethics.

Primary updates to 5-1 included adjustments reflecting changes in today’s technology and keeping the document current with best business practices.

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

CASE Winter Member Meeting SAVE THE DATE!

CASE is revamping their meetings. The design of the meetings will be used to encourage all members to attend different breakout sessions along with a project discussion and a roundtable on unique business practices challenges faced by structural engineering firms. The 2020 CASE Winter Member Meeting is scheduled for February 27-20, 2020, in New Orleans, LA. More information and registration information will be published in December. Questions? Contact Heather Talbert (htalbert@acec.org).

Follow ACEC Coalitions on Twitter – @ACECCoalitions.

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News of the Council of American Structural Engineers CASE Summer Membership Meeting Update

CASE convenes two membership meetings a year for continuing education and networking. Over two dozen CASE members and guests attended the recent meeting in Atlanta, GA, June 13-14, making this another well attended and productive meeting. During the meeting, members had the opportunity to hear about the Mercedes-Benz Stadium Structural Design and Delivery from Richard Saunders, S.E., P.E., and Matt Breidenthal, P.E., S.E., LEED AP from HOK Atlanta. Linda Bauer Darr, ACEC President and CEO, engaged CASE members in discussion regarding the future direction for ACEC and Coalitions. CASE members also attended break-out sessions with the CASE Contracts, Guidelines, Toolkit, and Programs and Communications Committees.

Current initiatives include: I. Contracts Committee – Chair: Brent Wright (brent@wrighteng.net) • CASE Commentary A on AIA Document C401 to legal review • Reviewing CASE Agreements #1 through Agreement #12 II.Guidelines Committee – Chair: Kevin Chamberlain (kevinc@dcstructural.com) • Structural Engineer’s Guide to Working with a Geotechnical Engineer • Seismic Engineering Business Practices for the Structural Engineer • Guideline 962-D: Guideline Addressing Coordination and Completion of Structural Construction Documents III. Programs and Communications Committee – Chair: Nils Ericson (nericson@m2structural.com) • Submitted session topics for the 2020 NASCC Steel Conference; AISC liked both and has given us the option of doing both • Finalized CASE’s three sessions at the 2019 ACEC Fall Conference • Discussed the option selected for submission for the 2020 SEI Structures Congress • Discussed schedule changes and speakers/topics for the 2020 CASE Winter Meeting: Thursday night local project highlight, Friday morning breakfast roundtable, Friday lunch War Story IV. Toolkit Committee – Chair: Brent White (brentw@arwengineers.com) • Finished updates to the current tool: Tool 5-1: Guide to the Practice of Structural Engineering • Finished the following new document: Tool 5-6: Lessons Learned

And the Scholarship Winner Is….

The CASE scholarship, administered by the ACEC College of Fellows, is awarded every year to a deserving student seeking a Master’s degree in an ABET-accredited engineering program. Since 2010, the CASE Scholarship program has given over $29,000 to engineering students to help pave their way to a bright future in structural engineering. CASE strives to attract the best and brightest to the structural engineering profession, and educational support is the best way we can ensure the future of our profession.

The 2019 winner, Tyler Wilfong, will graduate in May 2020 with a Master’s Degree in Structural Engineering from California State University, Fresno.

Manual for New Consulting Engineers An HR Favorite for New Hires

ACEC’s best-seller, “Can I Borrow Your Watch?” A Beginner’s Guide to Succeeding in a Professional Consulting Organization offers new engineers a head start in the business of professional consulting. This essential guide is tailored to the unique needs of engineering firms, and the skills and experiences rookie consultants need to be successful in a large organization, including: • Proposal Preparation • Project Management

• Financial Management • Client Relationships • Staff Management

With over 140 pages of consulting expertise, this resource is the perfect addition to any new staffer’s welcome pack or in-house orientation.

It can even be a useful resource for more seasoned engineers looking to refine their skills. To order this book, go to www.acec.org/bookstore.

Bulk ordering is available; for more information, contact Maureen Brown (mbrown@acec.org).

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SOFTWARE updates Aegis Metal Framing Phone: 314-851-2200 Web: www.aegismetalframing.com Product: Ultra-Span Floor and Roof Trusses Description: Each Ultra-Span floor or roof truss is designed to take advantage of the greatest strength per pound of any CFS available. Add in the ease of construction the Ultra-Span design brings and your project is positioned for success.

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IES, Inc. ASDIP Structural Software Phone: 407-284-9202 Web: www.asdipsoft.com Product: ASDIP Suite Description: A simple and intuitive software that includes four packages for the design of concrete and steel members, as well as foundations and retaining walls. ASDIP will help you design your structural members in less time. Do it faster, do it right.

CADRE Analytic Phone: 425-392-4309 Web: www.cadreanalytic.com Product: CADRE Pro 6.9 Description: Finite element structural analysis.

Loading conditions include discrete, pressure, hydrostatic, seismic, and dynamic response. Features for presenting, displaying, plotting, and tabulating extreme loads and stresses across the structure and across multiple load cases simultaneously. Basic code checking for steel, wood, and aluminum. Free fully functioning evaluation version available.

Dlubal Software, Inc. Phone: 267-702-2815 Web: www.dlubal.com Product: RFEM, RWIND Simulation Description: Includes wind tunnel numerical simulations of wind flow on all structures.

Integrate resulting wind pressures into the FEA program RFEM for further design of steel, concrete, wood, CLT, aluminum, glass, and fabric/membrane structures according to USA/International standards. Wind loading on specialty structures is now possible with RWIND Simulation.

ENERCALC, Inc. Phone: 800-424-2252 Web: enercalc.com Product: Structural Engineering Library (SEL), RetainPro, ENERCALC 3D, ENERCALC SE, STRUCTURE, EARTH Description: ENERCALC had a big summer after a long spring season of planting and tending to our software garden. A big harvest of substantial updates are available, including build 12 for SEL (lots of updates), a major update for RetainPro's segmental retaining wall module, and major additions to ENERCALC 3D.

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Phone: 800-707-0816 Web: www.iesweb.com Product: VisualAnalysis Description: Thousands of engineers use VisualAnalysis to analyze and design. Model just about any structure and get results you can trust.

VisualAnalysis is customer-proven for over 25 years. The latest version is an excellent investment at about $5/day. Get a free trial to see for yourself.

Meca Enterprises, Inc Phone: 918-258-2913 Web: www.mecaenterprises.com Product: MecaStack Description: Design of steel cylindrical stacks. Allows users to quickly model and analyze a self supported or guy wired supported steel stack. Provides a 3-D graphical representation of the stack being analyzed and handles many common design codes used to design stacks around the world.

Qnect LLC Phone: 512-814-5611 Web: www.Qnect.com Product: QuickQnect Description: An intelligent, cloud-based connection app gives fabricators, detailers, and engineers fast and flexible connections with significant cost and schedule savings. In minutes, users can connect most steel buildings without capital cost and with minimal initial training. Two important benefits of Qnect include: Preference Optimization and Bolt Optimization.

RISA Phone: 949-951-5815 Web: risa.com Product: RISAFloor Description: Designs and optimizes building systems constructed of steel (composite and noncomposite), open web steel joists, cold-formed steel, as well as combinations of materials. Version 14 includes new and updated steel vibration checks for steel joists and composite beams, and as LRFD design according to the AWC-NDS 2015/2018 codes.

Product: RISA-3D v18 Description: Provides engineers with a fresh new take on the most popular 3-D general analysis and design software available. With a completely redesigned interface, robust graphical modeling tools, expanded detailed reports, and multi-core processing, RISA-3D v18 allows engineers to work more efficiently and get the most out of the software.

StructurePoint Phone: 847-966-4357 Web: structurepoint.org Product: Concrete Design Software Suite Description: StructurePoint, formerly the PCA Engineering Software Group, offers concrete design software programs updated to ACI 318-14 for concrete buildings, concrete structures, and concrete tanks. Reinforced concrete structural software includes programs for design of columns, bridge piers, beams, girders, one and two-way slabs, shearwalls, tilt-up walls, mats, foundations, tanks, and slabs-on-grade.

Product: spLearn Description: StructurePoint licensed structural engineers have decades of experience with reinforced concrete design. As such, we have multiple resources on our website for the structural engineer to benefit, including: detailed design examples, technical articles, video tutorials, webinars, and more. Visit our website to learn more and request a webinar or consultation.

Trimble Phone: 678-737-7379 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: Fully automated and packed with unique features for optimized concrete and steel design, Tekla Structural Designer helps engineering businesses win more projects and maximize profits. From quick comparison of alternative design schemes through costeffective change management and seamless BIM collaboration, Tekla Structural Designer can transform your business.

Victaulic Phone: 610-923-3771 Web: www.victaulicsoftware.com Product: Victaulic Tools for RevitÂŽ 2020 Description: Engineers and contractors looking to boost their BIM are turning to Victaulic Tools for Revit to route more efficiently and fabricate faster.

The newly released VTFR 2020 features provide improved functionality in fabrication spooling, single click system assignment, and tracking ability for each fabrication package, including fabrication and shipping dates.

Listings are provided as a courtesy, STRUCTURE is not responsible for errors.

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