STRUCTURE magazine | December 2014 by structuremag

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STRUCTURE

NCSEA EXCELLENCE IN

December 2014 Soils & Foundations

CONTENTS

FEATURES

December 2014

Reaching New Heights in Los Angeles

COLUMNS

By Gerard M. Nieblas, S.E.

Rising out of a 90-foot deep excavation in the earth, a new high rise office/hotel building will dominate the skyline of Los Angeles. Bounded by Wilshire Boulevard and Francisco to the north, and 7th Street and Figueroa to the south, the Wilshire Grand project takes up an entire city block.

7 Editorial A Bold Vision: Educating Tomorrow’s Leaders and Innovators

By David J. Odeh, S.E., P.E., SECB

9 Structural Design Subgrade Modulus – Revisited

Shoring Up the Past, New York City Style

By George Aristorenas, Ph.D., P.E. and Jesús Gómez, P.E., D.GE

16 Structural Rehabilitation

By Alan M. Rosa, P.E. and Stephen Lehigh

The design of temporary shoring for existing buildings offers the engineer challenges on multiple levels, especially on vintage structures. This article presents a project that involved temporary shoring of an exterior bearing wall and storefront of a depression-era six-story apartment building located in midtown Manhattan.

Divine Design: Renovating and Preserving Historic Houses of Worship – Part 1 By Nathaniel B. Smith, P.E. and Milan Vatovec, P.E., Ph.D.

41 Building Blocks Cellular Concrete

By Scott M. Taylor, P.E.

NCSEA Excellence in Structural Engineering Awards

The NCSEA Excellence in Structural Engineering Awards program annually honors the best examples of structural ingenuity from around the world. The winners of the 2014 program were announced at the NCSEA annual meeting in September. Read about the structural solutions developed for these unique projects, and join NCSEA in congratulating these exceptional winners.

DEPARTMENTS 46 InSights Building Increased Productivity Using the Cloud By Sam Liu

48 CASE Business Practices CASE on Contracts – Part 1 By Steve Schaefer, P.E.

58 Structural Forum Rethinking Engineering Licensure

A Joint Publication of NCSEA | CASE | SEI

STRUCTURE

By Kip Gatto, P.E., S.E.

NCSEA EXCELLENCE IN

STRUCTURAL ENGINEERING AWARDS

December 2014 Soils & Foundations

THE

COVER

The Chhatrapati Shivaji International Airport Terminal 2. The Headhouse Roof, supported by only 30 columns, produces a large column-free space ideal for an airport. The Terminal Building project is an NCSEA Outstanding Project winner. Photo courtesy of Robert Polidori, Mumbai International Airport Pvt. Ltd. See page 33 of this issue.

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

STRUCTURE magazine

December 2014

IN EVERY ISSUE 8 Advertiser Index 50 Resource Guide (Earth Retention) 52 NCSEA News 54 SEI Structural Columns 56 CASE in Point

Editorial

A Bold Vision: Educating Tomorrow’s new trends, new techniques and current industry issues Leaders and Innovators By David J. Odeh, S.E., P.E., SECB, F.SEI

hat inspired you to become a structural engineer? For me, it was a fascination with the great buildings of history, like the Parthenon and the Eiffel Tower, and the ingenuity and creativity of the civilizations that built them. Starting with that early inspiration, I have always been driven by a desire to create new structures that have a positive impact on the way people live. Regardless of why we chose structural engineering as a career, it is this underlying passion that yields our most impactful ideas and accomplishments. If we want the future of our profession to be one of leadership and innovation, then we need to better harness this energy by changing the way we educate and train young structural engineers. For the last fourteen years, I have taught a class in structural design for civil engineering students in their senior year of undergraduate study. Often, this class is the first glimpse these students get into the real world of professional practice. But while the practice of structural engineering has changed dramatically over the time I have taught this course, the way we prepare our students to enter the profession has been largely stuck in “neutral” for more than a generation. Fundamentally the system is still based on an undergraduate degree in civil engineering, followed sometimes by a master’s degree with more specialized technical coursework. Undergraduate degree programs are highly constrained by ABET, the organization that accredits most engineering programs, through prescriptive content requirements that must typically be met in a four-year program. These requirements allow minimal opportunity for students to explore areas outside of their chosen field. Most core courses are technical in nature and, with no formal internship or residency requirements, many young engineers become licensed to enter professional practice with limited practical experience or knowledge of disciplines outside of civil and structural engineering. To judge the effectiveness of these programs, consider what skills will be rewarded by the economy of the future. Typical structural engineering tasks like stress analysis, prescriptive code-checking, member size selection, and detailing will be increasingly handled by automated computer programs or lower-cost technicians, perhaps working remotely. To truly lead and innovate, structural engineers must be decision-makers instead of technicians. They must be able to leverage the output of computer models to create innovative conceptual designs and new solutions to difficult problems, or create new paradigms that apply technology from many core fields like materials science, solid mechanics, machine design, mathematics, and physics. This will require a mastery of the classical methods, but also new skills that respond to the changing dynamics of professional practice. To innovate, structural engineers must also learn to operate in a more collaborative and interdisciplinary manner. We will need to move beyond working alone on calculations and specifications in our offices, and contribute to a more holistic and integrated design and construction process. The industry is increasingly turning to newer and more collaborative approaches to construction such as “Integrated Project Delivery”, a contractual method in which designers, contractors, and owners align their goals and work in highly collaborative teams to tackle the complex problems presented by construction projects. On such teams, structural engineers might be “co-located” with architects, builders, and other engineers in rooms with high-tech displays of computer models where teams jointly develop design solutions. STRUCTURE magazine

Finally, to lead in the global economy, structural engineers must be able to operate in multiple languages and cultures, and have a broader understanding of different building systems in use throughout the world. In one of my firm’s recent projects located in the United States, the entire steel detailing package was completed by a team operating out of the Philippines. While initially concerned about this arrangement, I was eventually impressed by the ability of these detailers to communicate with our engineers and efficiently understand and execute our design. American structural engineers must similarly adapt their unique skills to a broader worldwide marketplace if we hope to remain competitive in the global economy. SEI is committed to addressing this challenge at its roots, and engaging in an effort to re-imagine the educational system to better align it with the vision for the future. Earlier this spring, the institute created the new “Committee for the Reform of Structural Engineering Education” (CROSEE) with a mission to engage with key stakeholders from both academia and the profession to create bold, new initiatives to transform structural engineering programs. CROSEE will focus on re-thinking undergraduate education, exploring the concept of new “professional schools” for structural engineers, creating new and more formalized models for engineering internship programs, and strengthening the links between academics and practice. Recognizing that change in academia is difficult and will face numerous obstacles, the committee intends to begin its work with workshop sessions designed to frame the key issues and identify both short-term and long-term goals for reform. If you are passionate about structural engineering education and the future of our profession, consider some ways you can get involved in this initiative. Stakeholder workshops will be a great way to contribute your ideas and opinions. Agree or disagree, this is your chance to influence the future of our profession. Additionally, as a key strategic initiative of SEI, the SEI Futures Fund is investing in CROSEE by providing seed funding for its first stakeholder workshop. If you believe, like I do, that our educational system needs to evolve to a new model of leadership and innovation, please consider making a gift to the Futures Fund this year. We can only imagine what the inspiring structures of tomorrow will be. Perhaps we will create buildings made from new materials that are better able to withstand natural disasters and improve public safety; conceive of new classes of structures that seamlessly blend with elements of mechanical systems to improve energy efficiency and reduce the impact of construction on the global climate; or invent more humble buildings that revolutionize the availability and affordability of housing for the world’s growing population. To remain at the forefront of these advances, future structural engineers must be critical and creative thinkers fueled by a passion to solve the world’s great challenges. Let’s take action to reform our educational system today to build a vibrant and engaged profession for the future.▪ David J. Odeh, S.E., P.E., SECB, F.SEI, is the current Vice President of the Structural Engineering Institute of ASCE. He is a principal at Odeh Engineers, Inc. of Providence, RI, and also serves on the adjunct faculty in the School of Engineering at Brown University.

December 2014

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STRUCTURE® (Volume 21, Number 12). ISSN 1536-4283. Publications Agreement No. 40675118. Owned by the National Council of Structural Engineers Associations and published in cooperation with CASE and SEI monthly by C3 Ink. The publication is distributed free of charge to members of NCSEA, CASE and SEI; the non-member subscription rate is $75/yr domestic; $40/yr student; $90/yr Canada; $60/yr Canadian student; $135/yr foreign; $90/yr foreign student. For change of address or duplicate copies, contact your member organization(s) or email subscriptions@STRUCTUREmag.org. Note that if you do not notify your member organization, your address will revert back with their next database submittal. Any opinions expressed in STRUCTURE magazine are those of the author(s) and do not necessarily reflect the views of NCSEA, CASE, SEI, C3 Ink, or the STRUCTURE Editorial Board. STRUCTURE® is a registered trademark of National Council of Structural Engineers Associations (NCSEA). Articles may not be

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December 2014

he Subgrade Modulus, also known as the Modulus of Subgrade Reaction, is a stiffness parameter typically used in defining the support conditions of footings and mat foundations, such as that shown on Figure 1. The parameter is expressed in units of [Force]/[Length]3. Physically however, it is defined as the (contact) bearing pressure of the foundation against the soil that will produce a unit deflection of the foundation. The use of the parameter implies a linear elastic response, and therefore in design the pressure generated by the subgrade modulus is always limited by the allowable bearing pressure of the soil. In practice, the parameter is often recommended by the Geotechnical Engineer and used by the Structural Engineer for analysis of the structure. The structural analysis is not only used to gain insight into the settlement of the structure, but also provides consideration of settlement-induced stresses within the structure. In a structural analysis process, the subgrade modulus is typically utilized to obtain a vertical spring constant ([Force] / [Length]) by multiplying the subgrade modulus with the tributary area of the spring support elements. As a parameter that spans the geotechnical and structural realms, the subgrade modulus has been used and abused in practice, to a point where engineers tend to forget the physical meaning of and implications of the use of the parameter. This article will revisit the concept of the Subgrade Modulus by presenting and discussing common misconceptions of the parameter.

Misconceptions Statement 1: The Subgrade Modulus is a soil property. False. The subgrade modulus takes its theoretical origins from the formulation of Winkler-type

beams-on-elastic-foundations (Hetenyi 1946). The subgrade modulus is a lumped constant of integration of the differential equation of a beam supported by elastic springs. It is a function of the following: 1) Soil elastic properties: Modulus of Elasticity, Es, and Poisson’s Ratio, νs. 2) Foundation plan dimensions: Length, L, and Width, B. 3) Foundation stiffness: Modulus of Elasticity, Ef, and Moment of Inertia, If. 4) Other indirect factors: Compressible soil layer thickness, Hs, and depth of foundation below ground surface, D. As early as 1955, Terzaghi had suggested a conversion factor that involves the ratio of the size of footings to that of a plate load test to obtain the appropriate subgrade modulus for the footing. This implies that, for a given soil, the subgrade modulus is inversely proportional to the size of the footing. It can be concluded from the above that an adequate evaluation of the subgrade modulus requires both geotechnical and structural information.

Structural DeSign design issues for structural engineers

Subgrade Modulus – Revisited

Statement 2: The Subgrade Modulus is constant beneath the foundation. False. The ratio of the bearing pressure to the settlement within the footprint of the foundation varies according to a number of factors. Some researchers (Dey et al. 2008) have proposed formulations that include confining stress effects on the stiffness of granular soil, which generally decreases from the center of the foundation to the edges. However, in the opinion of the authors, the most dominant factors causing non-uniformity of the subgrade modulus beneath the foundation are the bearing pressure distribution and deformation compatibility mode. continued on next page

George Aristorenas, Ph.D., P.E., is a Technical Principal of the Geostructural Group of Schnabel Engineering, Inc. Dr. Aristorenas specializes in the analysis and design of soil-structure interaction problems, using advanced analytical and numerical techniques. He may be reached at garistorenas@schnabel-eng.com. Jesús Gómez, P.E., D.GE, is a Vice President at GEI Consultants in West Chester, Pennsylvania. Dr. Gómez is an Adjunct Professor at Drexel University. In April 2011 he was honored by CE News Magazine as one of seven individuals on the “Power List of people advancing the Civil Engineering profession”. He may be reached at jgomez@geiconsultants.com.

Figure 1. Mat foundation for a building under construction.

STRUCTURE magazine

By George Aristorenas, Ph.D., P.E. and Jesús Gómez, P.E., D.GE

The distribution of the bearing pressure, even for a uniformly loaded finite foundation, is affected by the stiffness of the foundation as it settles, and the settlement profile. Consider the cases illustrated below. For a very flexible foundation, the uniformly applied load essentially produces a uniform bearing pressure, as shown on Figure 2a. However, by compatibility of deformation at the edges of the foundation, i.e., the settlement profile cannot be discontinuous at the edges, the foundation does not settle uniformly, producing a maximum settlement at the center and minimum at the edges. Taking ratios of bearing pressure to settlement suggests that the maximum subgrade modulus occurs at the edges of the foundation. On the other hand, a uniformly loaded very stiff foundation will essentially settle uniformly. However, because the edges of the foundation represent an abrupt change in stiffness causing a discontinuity in the slope of the settlement profile, the bearing pressures spike at the edges and decrease as the center of the foundation is approached, as shown on Figure 2b, noting that the bearing pressure at the edges may taper off to the bearing capacity if it is approached. The areas of the bearing pressures of Figures 2a and 2b are equal, but the intensity of the bearing pressure underneath a stiff foundation varies. Taking ratios of bearing pressure to settlement for a very stiff foundation, it is observed that the subgrade modulus also increases towards the edges of the foundation. The non-uniformity of the settlement profile, even under a uniformly loaded flexible foundation, is primarily caused by the soil deformation mode along the foundation as

imposed by continuity of settlement. Under the center of the foundation, the primary deformation mode is vertical compression. However, at the edges of the foundation, the soil is also undergoing shear distortion in addition to compression. This combined deformation mode produces a stiffer net vertical response from the soil, thereby resulting in a smaller settlement. Furthermore, the zone of influence, or stress bulb, of the bearing pressure is shallower at the edges than at the center of the foundation. A constant subgrade modulus used under a uniformly loaded very flexible foundation will result in a uniform settlement, which is clearly erroneous. To capture the intrinsically multi-dimensional nature of the deformation mode, as opposed to a purely vertical mode using vertical subgrade moduli, some researchers (e.g. Teodoru 2009) have developed a two-parameter formulation of beams-on-elastic-foundations involving the subgrade modulus and another parameter which considers the shear distortion of the soil and an assumption of the curved deformation pattern. Note also that, with finite element software more readily available, it may be more efficient to model the soil as solid finite elements as opposed to springs, thereby encompassing all soil deformation modes underneath the foundation and beyond.

(a)

Figure 2. (a) Flexible foundation. (b) Stiff foundation. (a)

False. As a stiffness parameter, a low subgrade modulus will result in large settlement. Ultimately, however, the effect of differential

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(b)

Figure 3. (a) Constant subgrade modulus assumption. (b) Non-uniform subgrade modulus assumption.

Statement 3: Given the range of subgrade moduli underneath a foundation, it is more conservative to use the lowest value uniformly.

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settlement on the structure is perhaps more important. Consider the cases illustrated below in which a symmetrical structure is supported by a mat foundation. If the lowest subgrade modulus is used uniformly underneath a foundation, as shown on Figure 3a, the mat will essentially settle uniformly with possibly very minor curvature due to the concentrated loads from the columns. Thus, even though an upper bound estimate of settlement is calculated, the model does not adequately convey the bending of the mat foundation or the consequent distortion of the structure due to the actual settlement profile of the foundation. Using higher subgrade moduli at the edges of the mat foundation produces less settlement at the edges, as shown on Figure 3b. However, the foundation settles non-uniformly. Consequently, there is bending of the mat foundation and its curvature causes the structure to experience more distortion. These settlement-induced stresses in the foundation and structure are not captured in a uniformly settling foundation. It is for the same principle that differential settlement is considered more critical to a structure than absolute settlement. It should further be noted that the stiffness of the superstructure will tend to increase the stiffness of the foundation. The increased overall stiffness of the foundation will further enhance the nonuniformity of the subgrade modulus, as illustrated in Figure 2b.

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As mentioned earlier, it is more accurate to model the soil as solid elements

Figure 5. Subgrade modulus along diagonal line from center to corner. B = 52 ft, L = 130 ft, tf = 3 ft, Ef = 3600 ksi, Es = 600 ksf, νs = 0.35, Hs = 60 ft, D = 3 ft.

Figure 4. Distribution of subgrade modulus (kcf ). B = 52 ft, L = 130 ft, tf = 3 ft, Ef = 3600 ksi, Es = 600 ksf, νs = 0.35, Hs = 60 ft, D = 3 ft.

8.9 k-ft

6.4 k-ft

12.2 k-ft

7.8 k-ft

Y Z

28.6 k-ft

10.9 k-ft Load 3 : Bending Z :

Displacement

0.56"

Load 3 : Bending Z :

To illustrate the concept presented in Figures 3a and 3b (page 11), a 1-foot strip along the transverse centerline of the mat is modeled using the program STAAD.Pro. It is assumed that the mat supports a two-story, two-bay frame structure. Each story is 15 feet high, and each bay is 20 feet wide. The walls and slabs are 1-foot thick concrete structures, while the mat is assumed to be 1.5-feet thick. In addition to selfweight, a 100 psf uniform load is applied on the roof, slabs and mat. Construction staging is ignored. For the first case, a constant subgrade modulus of 20 kcf supports the mat, while the second case uses a non-uniform subgrade modulus varying from 20 kcf to 37 kcf as shown along the transverse section of Figure 4. The frame displacements and bending moments for these two cases are shown on Figures 6a and 6b, respectively. Comparing results from these two cases indicates that, as discussed before, larger settlements are observed for the case when a constant minimum subgrade modulus is used underneath the mat foundation, but larger structural bending moments result when a non-uniform subgrade modulus is used.

Conclusions 1) The subgrade modulus is a function of the soil stiffness and compressible

Displacement

0.54"

Figure 6a. Case 1 – frame displacement and bending moments; constant subgrade modulus of 20 kcf.

STRUCTURE magazine

18.2 k-ft

32.6 k-ft

0.61"

December 2014

0.36"

Figure 6b. Case 2 – frame displacement and bending moments; subgrade modulus varies from 20 kcf to 37 kcf.

layer thickness, as well as the foundation dimensions and stiffness. 2) The subgrade modulus is not constant underneath a foundation. 3) Using a constant, lower bound, value for the subgrade modulus underneath a foundation produces upper bound settlement but does not result in a conservative design of the structure.▪ The online version of this article contains detailed references. Please visit www.STRUCTUREmag.org.

248

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with appropriate material properties using finite element software to capture multidimensional deformation modes (Material behavior using finite elements become even more efficient for time-dependent consolidation and creep responses.). If, however, it is imperative that subgrade moduli be used in a structural model, there are certain approximations that can be performed to obtain the variation of the moduli underneath a foundation. One general procedure that may be adopted is as follows: 1) Use published linear elastic half space theories for calculating settlements resulting from a unit bearing pressure; e.g., settlement at a corner of a rectangular area. Use superposition as necessary to define interior points within the foundation. These theories are typically extensions of Boussinesq equation using the soil modulus, Es, Poisson’s ratio, νs, and the thickness of the compressible layer, Hs. 2) Apply appropriate influence factors for foundation shape and size (B and L), foundation embedment, D, and foundation stiffness (Ef and If or thickness tf). The foundation stiffness may also include the stiffening effects of the superstructure. 3) Calculate the inverse of the settlement from a unit bearing pressure; this is the subgrade modulus at the particular location. For instance, following the theory of elasticity presented in Das et al. (2009), the contours of subgrade modulus for a quadrant of a rectangular mat is shown on Figure 4. The distribution of subgrade modulus along the foundation’s diagonal line from the center to the corner is shown in Figure 5. Both figures show that the use of elastic half space theories also support the statement that the subgrade modulus is not constant beneath a foundation, and the subgrade modulus increases at the edges of the foundation.

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Structural rehabilitation renovation and restoration of existing structures

erforming renovation or restoration work on historic houses of worship presents a unique set of challenges for design professionals, and in particular structural engineers. These structures often feature large open-space areas, archaic structural systems and hard-to-define load paths, and varying degrees of deterioration or distress (often lack of maintenance and upkeep driven). All of these factors can make even the most simple-seeming renovation projects difficult, unique, and, in some cases, even stressful. Depending on the scope of planned renovations, structural upgrades aimed at preserving safety and mandated by building codes may also be triggered, which can be hard to implement or cost-prohibitive for structure types typical for historic houses of worship. However, renovating older, historic buildings to keep them functional and to equip them with modern amenities is a necessary undertaking. Understanding the inherent challenges at the outset of a project is key to making the renovations successful. Historic houses of worship are commonly part of the social fabric of neighborhoods, and it is important to preserve them for the benefit of the community, as well as for their architectural significance. This article discusses commonly encountered structural issues on renovation projects of this type, and provides guidance on ways to address them. Part one of this series focuses on foundations. Parts two and three, to be published in upcoming issues of STRUCTURE magazine, will focus on wall and roof systems, respectively.

Divine Design: Renovating and Preserving Historic Houses of Worship Part 1: Foundations By Nathaniel B. Smith, P.E. and Milan Vatovec, P.E., Ph.D.

Nathaniel B. Smith, P.E., is a Senior Project Manager at Simpson Gumpertz & Heger’s office in New York City. He serves as Project Manager on numerous projects involving repair and rehabilitation of houses of worship. He can be reached at nbsmith@sgh.com. Dr. Milan Vatovec is a Senior Principal at Simpson Gumpertz & Heger Inc. He serves as the Principal-in-Charge of numerous repair and rehabilitation projects. He can be reached at mvatovec@sgh.com.

Foundations Foundations are a critical component of any building structure; however, they also pose a significant maintenance and troubleshooting challenge as main foundation components are typically buried below grade and not readily accessible. Modern reinforced-concrete foundations typically require little if any maintenance over the life of a building. However, historic buildings commonly feature stone masonry and other archaic foundation systems that are more susceptible to damage due to movement or changed load paths, as well as deterioration due to exposure to moisture or other environmental factors. As a result, they require periodic evaluation, troubleshooting, and maintenance.

Stone Masonry Walls Unreinforced stone masonry is a brittle building material, and is susceptible to damage from

Typical stone masonry foundation wall.

almost any type of movement. The actual construction details and quality of construction invariably affect the robustness and in-service performance of the walls. Stone masonry walls come in a variety of styles, and usually reflect the vintage of the building, the materials that were readily available at the time of construction, and the style of the local craftsman that built the wall. High quality walls are typically constructed from cut-stone fully laid in mortar. The mortar in these walls helps to hold all of the pieces together, and enables them to act as a single, homogeneous component. Sturdiness of such walls is always greater than that of dry-laid stone walls. However, while dry-laid walls do not contain any (or much) mortar, if they were carefully constructed they could be fairly robust. A dry-laid stone constructed with cut stone will typically be more robust than a wall constructed from irregularly shaped stones. In the worst case, one may encounter a rubble stone wall that was constructed by basically dumping stone in a trench with some mortar to “hold things together.” Poor quality of construction of such walls makes them very susceptible to damage and performance issues. Movement of foundation walls can occur for a number of reasons; the two most common are related to settlement of the soil below the foundation, and/or lateral soil pressures on the cellar portion of the foundation walls. Because of the brittleness of masonry walls, differential settlement will typically result in cracks developing at mortar joints and in shifting of the stones themselves. This distress will often translate up the height of the building, and can also result in rotation or other out-of-plane movement of the walls above. Lateral soil pressures, on the other hand, often cause bowing or leaning of the masonry walls. The walls typically span vertically between the cellar floor and the first floor, and are incapable of resisting the induced bending without distress. Wall cracking can be locally repaired through a number of conventional methods (e.g. repointing, brick stitching, etc.). However, if cracking, vertical displacement, bulging or bowing of the foundation walls is significant, the wall may need to be rebuilt, or additional lateral support

16 December 2014

walls is to excavate test pits at select exterior locations, to observe the typical condition of the stone and mortar up close, and, if necessary, collect samples for subsequent testing. If sufficient deterioration of the mortar exists, repointing or strengthening of the wall may be necessary. When repointing, care should be taken to try to match the composition of the new mortar to the existing mortar. Modern mortar mixes use Portland cement as the binder, which is much stronger than limebased binders and creates a much stiffer mix. Using a stiffer mortar mix for repointing can result in unintended performance and cracking. Repointing the exterior of the foundation wall will also typically require excavation to expose the face of the wall, and is therefore an expensive exercise. If this work is undertaken, it is also a good time to consider providing a waterproofing or water-management system to minimize the contact of wall components with moisture, and to prolong the life of the foundation system. Upon completion of the work, proper site grading should also be provided to promote surface drainage away from the walls. Similar to the above-discussed methods, strengthening of deteriorated stone masonry walls may include construction of a reinforced-concrete (or shotcrete) liner wall on the inside face of the wall, providing supplemental framing, adding bracing, etc. Using a thin reinforcing-mesh, such as fiber-reinforced polymer sheets or laminates (FRP) is difficult given the typically uneven face of the stone and the variation in mortar joint locations.

Deep Foundations Depending on the local soil conditions, historic houses of worship may be founded on deep foundation systems. A commonly used historic deep-foundation system is untreated timber piles. Untreated wood piles have successfully been used for centuries throughout the world to transfer the weight of structures sitting on fill or other types of weak top strata to deeper soil layers capable of providing adequate support. Untreated timber piles can have a long service life if the tops of the piles stay submerged below the local groundwater elevation. However, groundwater elevations can be affected in numerous ways, but most critically by man-made actions: adjacent construction work, leakage into sewage systems, sumps installed within newer buildings located nearby, paving and diverting surface runoff away from foundations, etc. If the tops of the timber piles become exposed to oxygen due to lowering of the groundwater, the wood can quickly deteriorate due to fungal

STRUCTURE magazine

December 2014

Effects of differential settlement.

attack (rot). Wood destroying fungi ‘eat away’ at the wood cell structure, causing severe deterioration that can result in a significant loss of cross-section, change in mechanical properties, and a significant decrease in strength. This deterioration can lead to crushing of the wood fibers, pile failures, and localized or global differential settlement of the superstructure. If the deterioration is minimal or caught early, the piles may be able to be salvaged if the groundwater elevation can be restored and maintained to a level above the tops of the piles. This is typically accomplished by re-charging the groundwater to raise the water surface, installing coffer dams that surround the building footprint, etc. If the deterioration is too advanced, underpinning and re-supporting the building structure is typically required. The difficulty, of course, is that evaluating the condition and understanding the magnitude of the problem is often a difficult and expensive proposition: extrapolations of remaining service-life

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provided to prevent further distress or collapse of the wall. Rebuilding a wall will typically require extensive excavation on the exterior of the building, as well as temporary shoring of floor framing so that the wall can be removed and rebuilt. This option is frequently not cost effective, and consideration should be given to providing supplemental lateral support. Additional lateral support can be provided by constructing a liner wall on the inside face of the wall, or installing buttresses or tiebacks. The tradeoff may be that these supplemental elements could encroach on the interior or other usable space, but are likely less expensive than a rebuild. As with any below-grade space, the exterior of the masonry foundation walls are exposed to moisture. Stone and mortar are porous materials that absorb water; prolonged exposures will degrade the mortar, which is often lime-based and more susceptible to moisture-driven damage than current Portland cement-based mortars. Deterioration of mortar can lead to loosening and shifting of the stone elements, which may in turn cause distress in the structure above: brick masonry bearing walls may crack and bulge, floor framing can experience loss of bearing, or other distress may ensue. The stones themselves may also degrade from exposure to moisture; the amount of deterioration depends on the type of stone and level of exposure. Less dense and more porous stones such as sandstone and limestone will absorb more moisture and are therefore more susceptible to deterioration. This becomes especially critical if they are located near the ground surface and are subject to freeze-thaw cycles, which will accelerate the deterioration. More dense stone like granite, schist, or gneiss will absorb minimal amounts of moisture, and are much more resilient to deterioration. Evaluating the condition of stone masonry walls is difficult because typically only a portion of the interior face of the wall is exposed (or can be easily exposed by removing finishes), whereas the majority of exterior wall may be below grade. The interior face of the wall is typically also in the best condition because it is exposed to a relatively dry environment and, chances are, it has been maintained over its life (repointed, painted, etc.). Trying to extrapolate the condition of the exterior face of the wall based on the observed condition of the interior face is likely fruitless, given the potentially drastic exposure-condition difference; deterioration, if any, may not have spread through the thickness of the wall (foundation walls are typically on the order of 2 to 4 feet thick). The best way to evaluate the exterior of the foundation

Supplemental piles.

Cut and post underpinning method.

predictions often need to be made based on a very small sample size (limited number of test pits), yet the variability in damage amongst the population can be significant. Typical remedial approaches include either adding new pile elements (essentially circumventing the existing piles), or the cut-and-post method (underpinning). The cut-and-post method involves removal of the deteriorated tops of the piles, and replacement with concrete-filled steel posts wedged to the underside of the foundation or pile cap. When a group of piles is cut and posted, excavation is then filled with concrete to create a new cap and to fully encase the steel posts (therefore making the whole system less susceptible to water fluctuations). Planning and phasing of this approach is critical, especially for columns where temporary supports may need to be provided (especially if only a few piles support the entire column cap). Adding supplemental piles to the perimeter walls is an effective option in lieu of underpinning. There are numerous pile options available: push-pier, helical, micro-piles, etc. Several items need to be considered when providing supplemental elements to the existing system. First, whenever possible, piles should be added to both sides of the walls to avoid eccentricity issues. Second, the most challenging part of adding supplemental piles to masonry foundation walls is usually attaching the piles to the walls to be able to transfer the loads into the new system. This can be accomplished in several ways. One way is to place piles opposite each other adjacent to the wall, and to construct a connecting grade (needle) beam under the wall to transfer the load from the wall to the piles. However, this requires

extensive excavation and coordination with existing pile locations. Another option is to install the piles on opposite faces of the wall, to construct concrete caps atop each pile, and then install rods through the existing wall to each cap. The rods are then post-tensioned to “clamp” onto the existing wall to transfer the wall loads to the piles. For smaller loads, specialty or bolted brackets can be used to attach the piles to the wall. If none of these options work, independent foundations can be installed to support new structural framing to carry the increased loads Distress to the structure can also be due to eccentrically loaded existing piles. The crude historic methods used to install timber piles can result in piles not being in the proper locations. Eccentrically placed and loaded piles along perimeter walls, and especially at interior column pile caps, can cause distress and problems in service. The eccentric loading can cause rotation of the pile caps and leaning of the columns or walls extending up from the cap. The eccentricity can be addressed by adding piles to the cap in a similar manner as described above. Replacing the pile cap below a column may also be necessary in some situations, which can be extremely difficult. This typically requires that the column load be temporarily removed so that the cap can be removed and replaced. Extensive shoring,

Timber piles and grillage.

STRUCTURE magazine

December 2014

jacking, and monitoring is often needed to accomplish this, and can be prohibitively expensive. Supplementing the existing piles and maintaining the existing cap should be the first option considered. In some instances, timber grillages (horizontal timbers) were placed over the tops of piles during original construction to provide a flat surface to lay the base course of masonry. Grillages act as continuous beams to transfer loads from the masonry to the piles. As building loads are transferred through the timber grillage to the piles, the timber is loaded perpendicular to the direction of the grain. However, due to its cellular structure, wood is weak in the perpendicular-to-grain direction and may be inadequate to resist such loading. This weakness, combined with the relatively high concentrated loads at the piles, can lead to local crushing of the timber grillage and settlement of the structure. Timber grillage that is placed eccentric to the pile tops can cause further crushing and splitting of the wood, leading to larger localized displacements. The cut-and-post method of underpinning alleviates this condition as the tops of the piles and timber grillage are removed.

Increased Loading Renovations can often add load to the building foundations due to increased weight of finishes, additional proposed occupancy loads, addition of HVAC systems, and many other items that can be part of a typical renovation project. Accounting for and assessing how these additional loads affect the existing foundations, especially those featuring timber piles, can be difficult. Due to their age, there are often no available building plans, as-built documentation, or pile-installation records for historic houses of worship. However, expensive investigations to determine the type, layout, configuration,

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Conclusion Foundations are a critical part of any building. Problems with foundations, if not addressed, will almost invariably affect the superstructure, often in significant and irreversible ways. Understanding existing conditions, limitations, and expected in-service behavior of the foundation systems is especially important in historic structures such as houses of worship, and are a key to success for any renovation or restoration project.▪

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STRUCTURE magazine

December 2014

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and then capacity (through testing, analyses, etc.) of the existing foundations may not be needed, depending on the projected load increase. A reasonable rule of thumb, supplemented by engineering judgment and other considerations, is to take no further action if the additional building loads increase the foundation loads by less than 5%. For load increases above 5%, and in some cases up to 10%, determining the existing foundation layout and capacity is needed. This may require a potentially significant investigative effort: in-situ testing of stone or masonry, probing and sampling for subsequent testing, test pits to expose foundations, evaluation of support and soil conditions, soil and other testing, additional analyses, etc. If pile foundations are involved, typical size and configuration of the piles needs to be documented as well. A load test may also be prudent to ensure that the piles have sufficient capacity and that the increased loading (or suspected deterioration) will not cause settlement of the structure or other distress. Load tests on existing piles should be performed on piles along the perimeter walls, where the weight of the masonry wall above can be used as a reaction load. Typically, one of the piles exposed in the test pit is selected for the test. The top of the pile is removed so that a hydraulic jack can be installed and wedged between the pile and the underside of the wall. The jack is then used to load the pile in increments up to and beyond the current pile load, and the pile displacement is measured. The load and displacement measurements are recorded and evaluated, in a similar manner to any other pile load test, to determine an allowable capacity for the piles. Often, the existing foundation systems will not have any reserve capacity, and adding new loads to the building will require supplemental foundations. A number of effective options, some described above, can be used to achieve greater foundation capacity: wall or column strengthening, underpinning, increasing the bearing area, adding supplemental components (or piles), etc.

REACHING NEW

HEIGHTS IN LOS ANGELES By Gerard M. Nieblas, S.E., LEED AP

The grand pour (Guinness World Record).

he skies above downtown Los Angeles will see a new high rise office/hotel building by March of 2017. Rising out of a 90-foot deep excavation in the earth, the building will dominate the skyline of Los Angeles. The Wilshire Grand project takes up an entire city block. The site is bounded by Wilshire Boulevard and Francisco to the north, and 7th Street and Figueroa to the south.

Unbalanced soil loads.

Project Description The project is approximately 2,000,000 square feet with 900 hotel rooms, 400,000 square feet of office space and 45,000 square feet of retail space. The five-level subterranean parking covers the entire site and will accommodate 1,100 vehicles. The structure will have a rooftop pool with ocean views, highly advanced pressurized double decker elevators, an architectural roof top sail and a 200-foot tall architectural spire. The Tower structure is 73 stories, with the lower floors comprised of office space and the upper 40 floors as hotel rooms. The lateral system for the building is a concrete core wall with concrete filled steel box columns and structural steel framing outside the footprint of the core. The lateral system of the Tower is extremely slender, with a 30-foot wide core wall in the transverse building direction and nearly 1,000 feet tall. Along the height of the structure there are buckling restrained braced frames to reduce the overturning demands of the core wall on the mat foundation and to stiffen the structure for transverse wind and seismic drift. In order to meet the aggressive schedule, the project is fast track. The building permits were issued as Foundation Only, Foundation +, Superstructure part A to the 26th floor, and a “Building Permit Set” to the 73rd floor.

Rat slab with starter columns.

Shoring along 7th street.

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December 2014

Performance Based Design The upper 40 floors of the Tower are hotel rooms. To maximize views for all the rooms, it was architecturally important to provide floor to ceiling glass. A conventional code design of this structure would have required a secondary lateral system along with the core wall design. This system would have been some type of steel frame with deep members around the perimeter of the structure where views of the Pacific Ocean were most valued. The design team selected Performance Based design to eliminate this second lateral “back up” system. A secondary benefit to the Performance Based Design allowed the design team, along with the owner and the peer review panel, to set the performance objectives for the structure. Len Joseph with Thornton Tomasetti provided invaluable consulting on the performance based design of the Tower and its interaction with the podium structure.

Mat reinforcing with shear reinforcing.

Unbalanced Site Loads The northwest corner of the site is 39 feet higher than the southwest corner of the site. This unbalanced soil load results in an unbalanced horizontal force of approximately 25,000,000 pounds. This unbalanced force is approximately 80% of the base shear of the Podium superstructure and approximately 50% of the Tower base shear. In the east west direction, this unbalanced soil force accounts for 23% of the total base shear of the entire project. The addition of interior basement walls and fin walls off the core walls are required to resist these additional horizontal soil forces. These supplemental basement walls are supported on grade beams as large as 18 feet wide and 12 feet thick, with over 1 million pounds of reinforcing steel.

Elevator pits before top of mat reinforcing.

Shoring The excavation for the site encompassed an entire city block. There are 316 soldier piles around the perimeter of the excavation. The excavation along 7th Street is as close as 5 feet from the subway tunnel. To provide additional stiffness in the shoring system, rakers were added at 8 feet on center along 7th Street, adjacent to the subway tunnel. The x, y and z coordinates of the tunnel along the length of the excavation are monitored on a daily basis. This will continue until the entire podium structure reaches street level. Because of the removal of the soil adjacent to the tunnel, it has moved vertically approximately ½-inch.

Grade beam with one million pounds of reinforcing.

Lateral Foundation Analysis The Tower mat foundation was designed for two levels of earthquake resistance, as well as a 1,700 year wind event. The tower was designed for MCE (the Maximum Considered Earthquake – 2% probability of exceedance in 50 years, or 2,475 year return period) site specific response spectra utilizing several damping values, and for the SLDE (Service Level Design Earthquake – 50% probability of exceedance in 30 years, or 43 year return period) site specific response spectra utilizing several damping values. The SLDE earthquake design values were typically 15-20% of the corresponding MCE values. The Tower was designed for a suite of eleven time histories utilizing a Non-Linear Time History Analysis provided by our consultant, Thornton Tomasetti. continued on next page

STRUCTURE magazine

Cooling pipe for mat pour.

December 2014

Vibrating the mat pour.

Night time photo of grand pour.

The Podium structure and basement were designed for the prescriptive requirements of the 2010 California Building Code and ASCE 7-05 with a response spectra analysis. The interaction of the Tower structure with the podium structure and the framed parking levels was worked out by comparison of relative rigidities of each structure between Brandow & Johnson Inc. and Thornton Tomasetti.

Tower Foundation The foundations for the project are supported on bedrock. The allowable bearing pressures for sustained vertical loads under Allowable Stress Design were 12 ksf and 30 ksf for transient loads at localized areas from wind and seismic forces. The ultimate soil bearing pressure was 90 ksf for localized transient loads under the MCE design event. The footprint of the mat foundation extends past the outside of the Tower to reduce bearing pressures under the mat, and provide more stability for the foundation. Under service loads, the average net bearing pressure under the mat is 12 ksf. Under the maximum considered earthquake (2,475 year return period) the bearing pressures are as high as 58 ksf in small localized areas. The vertical loads from the core wall and the applied loads on the mat foundation are so great that it is anticipated that the 18-foot thick mat will dish approximately 1 inch under the weight of the core wall, and the mat will settle approximately 2 inches from the weight of the tower. The foundation for the Tower was poured in mid-February of 2014. It set a Guinness Book world record for the largest continuous concrete pour in history. The USC Marching Band led the first concrete truck. In total, 21,200 cubic yards of concrete were poured in 18.5 hours between Friday night and Saturday morning. The mat pour was 17 feet - 6 inches thick and had 6.7 million pounds of reinforcing steel. The original reinforcing in the bottom of the mat was 13 layers of #11 @ 6-inch on center each way. The reinforcing steel subcontractor was concerned about placing these bars and threading the headed #9 shear reinforcing through a clear space of 4½ inches. To alleviate this congestion, #18 bars with couplers were utilized. The bottom mat reinforcing was modified to 13 layers of #18 bars at an average of 15-inch on center. Since #18 bars may not be lapped spliced, mechanical couplers were utilized to join the bars. Each of these bars had to be hand spun onto the coupler and tightened with a torque wrench. In the top of the mat are 4 layers of #11 bars at 12-inch on center. To reduce the amount of reinforcing required, grade 75 ksi steel was utilized throughout the mat foundation. In the center portion of the mat, bars were spaced at 4 feet on center max in each direction for temperature expansion and contraction, and to provide support for the cooling pipe. STRUCTURE magazine

Concrete Temperatures Mat The heat of hydration was so great due to one continuous pour, the concrete temperatures were predicted to exceed 160 degrees without mitigation. To combat this, an active cooling system with on-site cooling towers was provided. Approximately 2,000 vertical loops of ¾-inch PEX pipe were manifolded together to remove heat from the concrete. This cooling system was left in place for two weeks for continued heat removal. Another concern with the temperature of the concrete was the differential temperature from the interior to the exterior of the mat. We were limited to a maximum 35 degree temperature differential from the exterior edge to the core of the mat. In order to keep the extreme edges of the concrete from “catching cold”, thermal insulation was added on the top of the mat to keep the concrete warm. This thermal insulation was left in place for two weeks. The Contractor waited patiently for two weeks to get on the mat to start forming the core wall. Core Wall The concrete shear walls at the base of the structure are 48 inches thick and heat of hydration was always a concern for the design team. Initially it was planned to build a mockup of the 48-inch wall, with thermocouples to monitor temperature and reinforcing to model congested areas of the walls. Due to the nature of the schedule, time did not allow for a mockup. To provide the design team with a level of comfort, the Contractor retained a concrete expert from Illinois. Computer models were made to simulate the heat of hydration, and the concrete mix and cement were analyzed. It was determined that the core wall concrete was DEF (Delayed Ettringite Formation) susceptible. DEF is a type of internal sulfate attack on concrete. In order for DEF to be an issue, three things need to be present: • Unfavorable Cement Chemistry – 12% fly ash in the concrete and unfavorable cement chemistry. • Long Term exposure to water – concrete core wall exposed to the elements for 1½ to 2 years. • Temperatures over 160 degrees – with a large amount of cement in the mix, a great deal of heat of hydration, and warm summer temperatures in Los Angeles, this was an issue.

Insulating the mat for two weeks to keep extremities warm.

December 2014

First lift of corewall reinforcing.

Typical corewall reinforcing.

To avoid DEF, it was necessary to chill the concrete mix so that concrete temperatures would never exceed 160 degrees. Los Angeles had numerous days where the ambient air temperature has exceed 100 degrees. Typically concrete can be delivered at point of placement as warm as 90 degrees; to avoid DEF, concrete delivery temperatures were limited to 70-75 degrees. The reduced concrete delivery temperature retarded the mix from maturity, which complicates the 4-day cycle of the concrete core wall. The Contractor’s schedule requires that the form system be jumped 12 hours after the pour. With lower delivery temperatures of concrete and slower maturity, the concrete is reaching approximately 1,000 psi at 12 hours. It was initially assumed that the concrete would reach 2,500 PSI at 12 hours. This created schedule problems with the coil inserts utilized in the core wall to jump the form system. Currently, test protocols are under development to demonstrate a safety factor of 3 in the design loads of the form system for 1,000 psi concrete.

Conclusion The Wilshire Grand Hotel/Office building will continue rising from the ground over the next three years. In late 2015 the structure should top out, with the remaining time devoted to the completion of the architecture and building skin. This will be the tallest structure west of the Mississippi. Outside of New York and Chicago, it will be the tallest structure in the United States. It will be the only highrise building in Los Angeles without a flat roof top, redefining the Los Angeles skyline with its elegant sail atop the structure.▪ Gerard M. Nieblas, S.E., LEED AP, is President of Brandow & Johnston Inc. Gerard may be reached at gnieblas@bjsce.com.

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Shoring Up the Past

New York CitY Style

By Alan M. Rosa, P.E. and Stephen Lehigh

he design of temporary shoring for existing buildings offers the engineer challenges on multiple levels, especially on vintage structures in New York City when not all the existing conditions can be known. This article presents a project that involved temporary shoring at the second floor of approximately ninety feet of exterior bearing wall and storefront of a depression-era six-story apartment building located on a busy intersection in midtown Manhattan. The building was continuously occupied during shoring operations. The design included an innovative rigid support of an excavation system designed for removal of existing foundation walls, and support of temporary shoring systems. The project, located at the corner of East 63rd Street and 3rd Avenue, is part of the construction of a new Metropolitan Transit Authority (MTA) 2nd Avenue Subway Line project. This building will serve as a new entrance to the 63rd Street/Lexington Avenue Station by way of a newly installed escalator entry.

Proposed Construction The proposed permanent design creates access to the lower level of the subway station adjacent to the building using an escalator at the northwest corner of the building. The access point exits at street level within the envelope of the existing apartment building. During the construction of the new entrance, the building will receive a new reinforced concrete foundation wall that will replace an existing stone rubble wall. The masonry bearing walls and the existing storefront above the street level will be replaced with a new perimeter steel support frame. The new foundation will include a reinforced concrete slab, at approximately the same elevation of the existing basement, that will ramp down fifteen feet below the basement level for the new escalator.

to any demolition, and their sequences were limited to occur after installation and preloading of the temporary support steel. A system utilizing eight 5-foot, 6-inch x 5-foot, 6-inch post-tensioned unreinforced concrete piers spaced at 9 feet on centers was developed. Hand excavated pits were advanced using horizontal sheeted timber rings forming a box, similar to conventional underpinning methods. The base of each pier was extended below the bottom of the proposed excavation to an adequate subgrade bearing strata. Once the concrete was poured and cured, the tops of the piers were post-tensioned using self-drilled rock anchors installed at a 1:4 slope to accommodate the proximity of the existing building foundation (Figure 1). The steeply sloped tiebacks were also advantageous to avoid the existing street utilities. The anchors were located at the center of the piers in a Polyvinyl Chloride (PVC) sleeve within the pier, and grouted into ledge rock. The embedment into rock ranged from twelve to fifteen feet and each tieback was tested to 133% of the anticipated 240 kip lock-off load, i.e. the design anchor load at the tallest pier. At the northwest corner of the building, the existing adjacent below grade station entrance framing was used for support of the temporary shoring system.

Temporary Shoring

Existing Building Construction Typical multi-story residential construction of this era consisted of wood floor framing, masonry bearing walls, and perimeter steel storefront framing. The estimated temporary shoring loads of this project at the second level varied from 8 kips per foot (kips/ft) to approximately 13 kips/ft of wall. The foundation consisted of mortared stone rubble foundation walls, with brick masonry piers at existing column locations within the basement. The interior of the building is supported by steel beams and columns on spread footings.

Support of Excavation A rigid support was required for both the support of the temporary shoring frames needed upon removal of the existing rubble foundation walls and for the deep excavation system below the basement level. Conventional methods were not possible due the proximity of the street to the building and the vast amount of existing street utilities. The supports of the excavation were required to be installed prior STRUCTURE magazine

Figure 1. Elevation of temporary shoring system at north storefront and bearing wall.

The existing building is classified by the MTA as a fragile structure, defined as the limit of damage allowed is no more than very slight. This is defined as damage that contains fine cracks (up to 1/32 inch wide) in the exterior wall façade that are easily treatable and damage that is generally limited to interior wall finishes. The restrictions for the temporary shoring requirements were many, and included stringent tolerances on the maximum and relative movement. A maximum limit of 1/8 inch, with a threshold limit of 1/16 inch in both the horizontal and vertical directions, was required. Of the variety of temporary shoring designs required on this project, including one for removal of a six story steel interior column, the two main systems discussed in this article will be one for the support of the existing perimeter beams over the storefront and another for the support of the existing brick bearing walls. At Storefronts Within the limits of the new entry, the existing structure was demolished up to the underside of the existing steel beams that support

December 2014

Figure 2. Typical A-Frame shoring at storefronts.

the masonry above and span the storefronts. Thus, any temporary shoring system must leave clearance for the installation of new perimeter beams and columns installed directly below the existing second floor perimeter steel framing. In addition, a system was required to allow the installation of a new concrete foundation wall to replace the existing rubble foundation wall. An A-Frame system consisting of compression struts and tension ties was developed (Figure 2). The exterior ends of the frames were supported on the post-tensioned concrete piers, and the interior ends of the frame were supported on a steel frame system which in turn was supported on 3-foot by 4-foot concrete piers to a depth of approximately thirty feet below

Figure 3. Elevation of northwest corner with post-tensioned pier supporting the A-Frames.

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STRUCTURE magazine

December 2014

the street level (Figure 3). The tops of the A-Frames were attached directly to the existing steel beams by welding the compression struts to the existing girder (Figure 4, page 28). The frames straddled the existing beam ends above the existing columns that were being removed so as to not change the existing support conditions of the beams; that is, one A-Frame at each beam end. The A-Frames were preloaded using hydraulic jacks at each side on the frame. The jacks were supported by channels connected to the main temporary girders just below the tension members of the frames. At other locations, it was possible to jack only from one side of the A-Frame. In these cases, the lateral movement of the frames at the apex due to the one-sided jacking was determined to be negligible. Jacking loads were limited to ninety percent of the calculated dead load plus a small allowance for live load throughout the building. Since each frame was jacked independently, the expectation was that little to no vertical movement would occur due to the restraint provided by the existing brick walls. Thus, it was important that the jacking loads be determined as precisely as possible, and that the A-Frames and supporting system would have a significant amount of extra strength available to confidently remove the existing steel columns supporting the perimeter storefront steel. Monitoring systems were installed to register any movements. As a result, all original building columns were removed successfully without any appreciable movement measured or cracking observed.

not practical given the various frame deflections required to preload the system. It was therefore determined that the best approach was to wedge-shim each needle beam at each end to the required vertical displacement and then to pack it with flat shims to provide uniform bearing support. The required displacement was determined from an estimate of the uniform wall load and the tributary width of an individual needle beam. In order to account for deformations in the piers and the steel columns, and the deflections of the supporting frames, a comprehensive structural analysis was performed on both the interior and exterior frames to determine the exact level of shims required for each needle beam. Shimming could not commence until the entire web space and the top flange was packed with grout so that the masonry bearing area was increased and the masonry

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Along East 63rd Street, a thirty-eight foot long section of an existing 16-inch thick brick masonry bearing wall was required to be removed to the same elevation as the adjacent storefront (Figure 5, page 28). Needle beams spaced at two feet on centers, on average, were utilized. As in the case of the A-Frames, the interior ends of the beams were supported on the steel frames, which in turn were supported on the 3-foot by 4-foot concrete piers. The exterior frames were supported on the post-tensioned concrete piers (Figure 4). At the second floor, there were four existing steel beams supported by the existing bearing wall that needed to be shored prior to wall removal. Hung beams adjacent to the wall being removed provided the support of the existing beams and were attached to the bottom flanges of the needle beams. Distribution beams adjacent and parallel to the exterior wall were required at the larger window openings, and at the existing fire escapes, to evenly distribute the wall load to all needle beams (Figure 6, page 28). In order to uniformly load the existing wall, jacking methods were

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At Bearing Walls

Figure 4. Typical A-Frame and needle beam construction sections at existing storefront and bearing wall.

Figure 6. Needle beam support at existing masonry bearing wall with window distribution beam.

this project. On this project, multiple prisms and rotational meters were strategically placed at the face of each building elevation. All instruments were measured continuously from a remote location. The tops of the post-tensioned concrete piers were monitored during preloading of the A-Frames and the needle beams, in anticipation of possible settlements and possible horizontal displacements due to relaxation of the post-tensioning anchors. Monitoring will extend to the end of construction. Figure 5. Post-tensioned concrete pier construction.

Conclusion

was not overstressed (Figure 6). Concrete piers were monitored for settlement during shimming operations, with the understanding that the required design shim thicknesses may need to be adjusted if settlement occurred. The heaviest loaded needle beams were shimmed to an estimated mid-span concentrated load of 24 kips. Once completed, the masonry wall was removed in sections starting directly under the bottom flanges of the needle beams. Removal was completed within two days with no movement or cracking registered.

The design of temporary shoring systems in New York City offers the engineer many challenges given special constraints, existing utilities and unknown conditions. Innovative, yet practical solutions are necessary to achieve the desired result, one that is cost effective and on time. A sound monitoring program is an essential part of the temporary shoring design and construction.▪ Acknowledgment: Contractor – Judlau Contracting, Inc., College Point, NY

Monitoring One of the more important aspects of this temporary support design was the monitoring of the existing building for displacement and rotation. With close monitoring and tight restrictions given for movement and rotation, it allowed adjustments to the design if unintended movements occur. Therefore, the implementation of a sound, well thought out monitoring program was an important design consideration for STRUCTURE magazine

Alan M. Rosa, P.E. (arosa@scs-pc.com), is a Principal and Stephen Lehigh (slehigh@scs-pc.com), is a Senior Project Structural Engineer at Structural Consulting Services, P.C., Brookfield, CT. December 2014

Formwork for Concrete Completely revised and updated; still the formwork reference of choice

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Excellence in Structural Engineering NCSEA 17th Annual Awards Program

he National Council of Structural Engineers Associations (NCSEA) is pleased to announce the following 2014 Excellence in Structural Engineering Awards. The awards were presented on the evening of September 19 during the Awards Program at NCSEA’s 22nd Annual Conference in New Orleans, LA. The awards have been given annually since 1998 and highlight some of the best examples of structural ingenuity throughout the world. All structures must have been completed, or substantially completed, within the past three calendar years. Awards were given in eight separate categories, with one project in each category being named the Outstanding Project. The categories for 2014 were: • New Buildings under $10 Million • New Buildings $10 Million to $30 Million • New Buildings $30 Million to $100 Million • New Buildings over $100 Million • New Bridge and Transportation Structures • International Structures over $100 Million • Forensic / Renovation / Retrofit / Rehabilitation Structures • Other Structures The 2014 Awards Committee was chaired by Carrie Johnson (Wallace Engineering Structural Consultants, Inc., Tulsa OK). Ms. Johnson noted: “We had a great group of judges from the Structural Engineers Association of Oregon this year, and some truly outstanding projects. They had the enormous task of evaluating a wide variety of projects from twenty different states and five different countries. The judges did an outstanding job of thoroughly analyzing each entry and thoughtfully discussing which ones should receive an award. Seeing the entries each year continues to make me proud to be a structural engineer.” Please join STRUCTURE® magazine and NCSEA in congratulating all of the winners. More in-depth articles on several of the 2014 winners will appear in the Spotlight Department of the magazine over the course of the 2015 editorial year. STRUCTURE magazine

2014 PANEl of JudgES The judging was held Tuesday July 22, 2014 at the offices of KPFF in Portland, OR. The 2014 awards jury from the Structural Engineers Association of Oregon included the following individuals: Rick Amodeo, P.E., S.E. AAI Engineers Joe Gehlen, P.E., S.E. Kramer Gehlen & Associates, Inc. Ron Kernan, P.E., S.E. KPFF Consulting Engineers Amit Kumar, P.E., S.E. City of Portland Mark Libby, P.E. HDR Engineering Brad Moyes, P.E., S.E. KPFF Consulting Engineers Trent Nagele, P.E., S.E. VLMK Ed Quesenberry, P.E., S.E. Equilibrium Engineers, LLC Tim Rippey, P.E., S.E. Tim Rippey Consulting Engineers Wade Younie, P.E., S.E. DCI Engineers

December 2014

Category 1 New Buildings under $10 Million

outStANdiNg ProJECt Jasper Place Library Edmonton, Alberta

fast + Epp

Jasper Place Library is a 15,000 square foot replacement of an existing facility. The striking new structure was built with the goal of becoming the new social heart in an older suburban neighborhood. Predominantly cast-in-place concrete on piles, the primary feature is the expressive curved plate concrete roof that spans the entire library space, punctuated with skylights. The overall result is a response to the changing needs of the Library of the Future.

Courtesy of Stephan Pasche.

Category 2 New Buildings $10 Million to $30 Million

outStANdiNg ProJECt Theatre for a New Audience at Polonsky Shakespeare Center Brooklyn, NY

robert Silman Associates

The Theatre for a New Audience is a laboratory for modern theatrical interpretation of classical plays. Its new home, a sleek glass and steel building in Brooklyn’s BAM Cultural District, is deceptively simple in form, belying its structural complexity and the intricate acoustical isolation that prevents the sounds of the subway running underneath and the traffic on the busy streets around it from interfering with the performances happening within. A cantilevered front façade allows the entire front lobby of the theater to hover above the plaza below, rather like a curtain being raised for a performance.

STRUCTURE magazine

December 2014

Category 3 New Buildings $30 Million to $100 Million

outStANdiNg ProJECt P750 Helicopter Maintenance Hangar San diego, CA

frankfurt Short Bruza Associates, PC

The U.S. Navy required a three squadron helicopter maintenance facility located along the northern waterfront at Naval Air Station North Island. With prime inward views throughout San Diego, this hangar had to be worthy of its location, reflect an equally positive image, become a significant part of the installation’s waterfront and a source of Navy pride. Structural engineers collaborated with the project team to deliver strong aesthetic solutions to the project’s numerous physical challenges including clear space, volume, environmental design factors and client requirements. This 112,000 square foot facility was successfully completed at an approximate cost of $50 million.

Courtesy of Heliphoto.net.

Category 4 New Buildings over $100 Million

outStANdiNg ProJECt Newport Beach Civic Center and Park Newport Beach, CA

Arup

The conceptual vision of architectural firm Bohlin Cywinski Jackson paired with the sculpted steel designed by Arup structural engineers celebrates the use of exposed structural steel as architectural form and function. New structures include the City Hall, Community Room, Council Chambers, expansion to the public library, parking garage, and four pedestrian bridges. The iconic curved wide-flange waved roofs, vierendeel trusses, and buckling restrained brace frames of the City Hall, and the large cantilevers of the Library roof and the San Miguel Bridge, allow the public to see the structure “at work” while providing memorable experiences.

Courtesy of David Wakely.

Courtesy of Nick LeHoux.

STRUCTURE magazine

December 2014

Category 5 international Structures over $100 Million

outStANdiNg ProJECt Chhatrapati Shivaji International Airport – Terminal 2 Mumbai, india

Skidmore, owings & Merrill llP

Chhatrapati Shivaji International Airport Terminal 2 adds 4.4 million square feet of new space to accommodate 40 million passengers per year. The primary design feature of the building is a long-span roof covering a total of 70,000m2 (83,720 square yards) over various functional requirements, making it one of the largest roofs in the world without an expansion joint. The Headhouse Roof, supported by only 30 columns, produces a large column-free space ideal for an airport. The Terminal Building also includes the largest and longest cable wall system in the world. The structural design prioritized modular construction for economy and facilitation of an accelerated construction schedule.

Courtesy of GVK.

Courtesy of Robert Polidori | Mumbai International Airport Pvt. Ltd.

Category 6 New Bridges and transportation Structures

outStANdiNg ProJECt Floating Cofferdam for Repair of the Washington State SR-520 Floating Replacement Bridge Seattle, WA

Ben C. gerwick inc.

Structural cracking in the new pontoons for the replacement SR-520 floating bridge required repair in a dry environment. A floating cofferdam was designed to act as a floating dry dock that seals against a bridge pontoon afloat. The cofferdam features two sliding side gates, a cofferdam-pontoon seal, and 28 struts with hydraulic jacks for load transfer. It is 96 feet wide, 44 feet long and 35.5 feet tall with a weight of 600 tons. The cofferdam was fabricated on a barge and side launched at the Lake Washington site.

Courtesy of Washington State Department of Transportation.

STRUCTURE magazine

Courtesy of Aequalis Photography.

December 2014

Category 7 forensic/renovation/retrofit/rehabilitation Structures

outStANdiNg ProJECt 680 Folsom Street San francisco, CA

tipping Mar

The transformation of 680 Folsom – a 1960s steel-moment-framed building that no one had wanted – into desirable office space involved a complete gut renovation, seismic retrofit, and expansion. At the behest of TMG Partners, a value-engineering effort impelled Tipping Mar to once again boldly innovate, reaching centuries into the past and oceans away to medieval Japan. The result? A unique isolative lateral system – unprecedented in modern engineering – that saved $4 million on a $110 million project and provided enhanced seismic performance.

Category 8 other Structures

outStANdiNg ProJECt East Station Plaza – Danseurs (Dancers) union City, CA

Simpson gumpertz & Heger inc.

The City of Union City, California sought to develop a civic plaza, which included a centerpiece – a terraced fountain with three bronze sculpture “Danseurs” on platforms positioned within the fountain. The fountain would be built 0.6 miles northeast from the Hayward fault line. With that in mind, Simpson Gumpertz & Heger suggested mounting the sculptures on base-isolated platforms – put them on a suspension with springs and shocks to reduce the lateral forces on the sculptures. Using isolated platforms, the architect and city were provided with an elegant solution to protecting their civic sculptures from earthquake damage for future generations.

STRUCTURE magazine

December 2014

AWArd WiNNEr – CAtEgorY 1 The Brelsford Visitor Center – Washington State University Pullman, WA KPff Consulting Engineers The 4,200 square foot Brelsford Visitors Center orients guests to WSU and serves as a vital resource for other attractions in the region. Pivoting display walls build public awareness, and support of the University’s lifechanging teaching, research, and outreach activities. The glazed pavilion is topped by an overhanging CLT roof that is supported by the 15-foot concrete “U” on one end and a 40-foot-tall steel plate tower on the other.

AWArd WiNNEr – CAtEgorY 1 The Dorrance K. Hamilton Rooftop Garden at the Kimmel Center for the Performing Arts Philadelphia, PA the Harman group, inc. The enclosure of the Dorrance K. Hamilton Rooftop Garden at The Kimmel Center is a structural glass gem within the barrel vault of Philadelphia’s premier Performing Arts Center. Structural elegance and simplicity were key to developing a workable supporting structure for the glass box, enclosing the space while maintaining the high level of vibration and acoustic separation necessary to the Perelman Performing Arts Center below.

AWArd WiNNEr – CAtEgorY 2 Denver Union Station Train Hall denver, Co Skidmore, owings & Merrill llP SOM Structural Engineers, working closely with SOM Architects, designed several steel and fabric pavilions for Denver Union Station Intermodal Hub. The focal point for the new station – the Train Hall structure – was conceived as an efficient and formally expressive means of clear-spanning 180 feet across multiple railway tracks. The primary structural system consists of eleven steel “arch trusses” spanning nearly 180 feet from a single large-diameter pin connection. The arch-trusses and cantilevered trusses support a tensioned PTFE fabric.

STRUCTURE magazine

December 2014

AWArd WiNNEr – CAtEgorY 2 “Trefolo” University Building forlì, italy Proges Engineering S.r.1 The so-called “Trefolo” is the set of paths that connect the lecture halls at the University Campus in Forlì, Italy. It consists of three twisting tubes with variations in height and plan. The three tubes (with a total length of about 100 meters or 328 feet) rest on irregularly spaced vertical elements (props and stairwell partition walls) with several significant spans. Structural challenges included aspects in relation to the structure’s behavior under static and seismic conditions. In addition, difficult site conditions presented numerous challenges during construction.

AWArd WiNNEr – CAtEgorY 2 University of Louisville Student Recreation Center louisville, KY rangaswamy & Associates, inc. With a growing urban campus, the University of Louisville student body saw an increasing need for additional intramural and recreation space. The steel framed $27 million Student Recreation Center encompasses 128,000 square feet and contains six new gymnasiums, a multi purpose court, an indoor cantilevered jogging track, and more. Due to space constraints on campus, the building has an irregular geometry which includes stacked gymnasiums and multiple cantilevers. Several innovative structural systems were required to meet the multiple framing complexities on this building.

AWArd WiNNEr – CAtEgorY 3 Krishna P. Singh Center for Nanotechnology – University of Pennsylvania Philadelphia, PA Severud Associates Consulting Engineers, PC The intra-disciplinary Singh Center for Nanotechnology ascends as a spiral to The Forum, which is a 68-foot cantilevered room. By design, it accommodates collaboration and sensitive nanotechnology research including clean rooms and a transmission electron microscope. The cantilevered Forum is designed to accommodate lectures and social events, with vibration considerations such as dancing. The stepping southern façade encloses the sunny galleria atrium with a curtain wall cut in two directions by a sloping roof.

Courtesy of Večerka/Esto.

STRUCTURE magazine

December 2014

AWArd WiNNEr – CAtEgorY 3 MAST Foundation Bologna, italy Proges Engineering S.r.1 MAST Foundation is a cultural and philanthropic institution that focuses on art, technology and innovation. Steel structures are used for the main building functions; secondary functions are underground construction in reinforced concrete. Steel structures forming the building are the synthesis of the research for specific solutions to complex problems. The result is that it is not possible to recognize the presence of structures in part of the building while, in another part of the building, structures emerge in all of their strength and elegance of expression.

Courtesy of Christian Richters.

AWArd WiNNEr – CAtEgorY 4 Music City Center Nashville, tN ross Bryan Associates, inc. Nashville is known as Music City USA, and when a new convention center was proposed, it was aptly named the Music City Center. Located in the rolling hills of Middle Tennessee, the architects incorporated both Music City and rolling hills themes into the design of the building. The grand ballroom is shaped like a guitar. The 14-acre roof is curved in two directions and includes a 4-acre vegetated green roof to mimic rolling hills. These features resulted in a stunning building and presented significant design challenges for Ross Bryan Associates, Inc.

AWArd WiNNEr – CAtEgorY 4 San Bernardino Justice Center San Bernardino, CA Skidmore, owings & Merrill llP The San Bernardino Justice Center (SBJC) is the largest project constructed for the Administrative Office of the Courts, and the first to embrace life-cycle analysis considering the structural performance and return on investment in a region of high seismicity. With extraordinarily high site-specific ground motions, SBJC utilizes base isolation bearings and dampers to manage large ground motions. SBJC features a steel superstructure with special moment frames and supplementary viscous damping devices. The triple-concave friction pendulum seismic isolation system, located on the mat foundation, accommodates 42 inches of lateral movement.

Courtesy of Bruce Damonte.

STRUCTURE magazine

December 2014

AWArd WiNNEr – CAtEgorY 4 Utah Museum of Natural History Salt lake City, ut dunn Associates, inc. Nestled in the foothills above Salt Lake City, the 163,000 square foot Natural History Museum of Utah houses a collection of 1.2 million artifacts. The building is composed primarily of exposed concrete with copper-alloy cladding. Between the copper, the lighter concrete and the metal panels, the building blends into the mountainside by using colors that complement its natural surroundings. Intended to teach and inspire visitors about the natural world and our place within it, the museum creates a distinct architectural and cultural significance for the state of Utah.

AWArd WiNNEr – CAtEgorY 5 JW Marriott Hanoi Hotel Hanoi, Vietnam leslie E. robertson Associates The Marriott International Hotel, Hanoi also serves as the home of Vietnam’s National Convention Center. This project consists of a nine story, five-star, 500 room Marriott hotel and attached parking garage. The estimated size of this waterfront project is 800,000 square feet. The complex building uses steel trusses combined with reinforced concrete. The building’s design takes its inspiration from the dragon, which evokes the rich heritage of Vietnam.

AWArd WiNNEr – CAtEgorY 6 San Francisco-Oakland Bay Bridge New East Span oakland, CA t.Y. lin international/Moffatt & Nichol, Joint Venture Located between faults capable of producing destructive earthquakes, the San Francisco-Oakland Bay Bridge New East Span is a regional lifeline structure with a 150-year design life, and is designed to open to emergency traffic within days after a major seismic event. It features engineering innovations and advancements such as shear link beams in the single tower, hinge pipe beams and specially-designed expansion joints in the bridge decks, and foundations that reach up to 300 feet below the water’s surface to anchor in stable soils.

Courtesy of T.Y. Lin International.

STRUCTURE magazine

December 2014

AWArd WiNNEr – CAtEgorY 7 140 New Montgomery San francisco, CA Holmes Culley With the latest analysis technology and an innovative strengthening scheme, Holmes Culley designed a seismic retrofit to preserve San Francisco’s first skyscraper. Using Performance Based Engineering, a full non-linear analysis model was developed to analyze the existing building. The new structural solution utilizes outrigger trusses distributed at two locations over the height of the building, supported by super-columns at the exterior, to maximize effectiveness of the core walls; and it satisfies the Secretary of the Interior’s standards for the treatment of historic properties. Courtesy of Henrik Kam 2013.

AWArd WiNNEr – CAtEgorY 7 Everyman Theatre Baltimore, Md Keast & Hood Co. The project to renovate historic Everyman Theatre in Baltimore, Maryland, revitalized an abandoned property for new use by a community theater organization. Encompassing historic preservation, creative design, construction craftsmanship, and good stewardship, the project did more than create a modern performing arts venue – it contributed to positive neighborhood and economic renewal in Baltimore’s West Side arts district. Structural design challenges included accommodating acoustics for two stacked theaters, isolating the structure from an adjacent train tunnel, developing a unique and cost-effective system to restore the deteriorated façade, and reacting to structural surprises and not one, but two, natural disasters.

AWArd WiNNEr – CAtEgorY 8 Richard Serra’s “7” Sculpture doha, Qatar leslie E. robertson Associates Located on a man-made peninsula in Doha, Qatar, Richard Serra’s sculpture “7” is composed of seven 4-inch thick, 80-foot high by 8-foot wide rectangular steel plates arranged as a heptagon in plan. Each plate leans and tilts towards the top of the sculpture. The material is intended to rust in a pattern conducive to the artist’s vision. Leslie E. Robertson Associates (LERA) determined the geometric layout of the sculpture in 3-dimensional software, reviewed the stability of the slender plates under thermal, wind, and seismic loads, and designed the connections between the individual plates and the sculpture’s supports.

STRUCTURE magazine

December 2014

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Building Blocks updates and information on structural materials

Too many Pipes! Using a lightweight flowable product saved significant time and labor.

espite the fact that cellular concrete has been used in the construction industry for nearly a century, it is not uncommon for designers to be unfamiliar with this versatile lightweight product. “What is this stuff?” and “Why haven’t I heard of this before?” are very common questions. The primary reason cellular concrete has gained popularity so slowly in the civil/structural market is that the manufacturers have focused on flooring and roofing for the past 50 years. Now that installers are casting a wider net due to the recent economic downturn, the civil/structural engineering world is starting to realize the vast benefits of cellular concrete. We are seeing the variety of uses expanding daily by enthusiastic and creative engineers everywhere. There are rumors of a Swedish patent for cellular concrete from 1923. If the patent is proven true, the origins of cellular concrete could be traced back to before 1923. Unfortunately, the actual origins remain unconfirmed. It has also been widely believed that cellular concrete was developed in Germany in the 1940s. We do

know it was brought to the United States in the 1950s as a lightweight floor leveling product.

What Is Cellular Concrete?

Cellular Concrete

Cellular concrete is a carefully crafted mixture of cement, water and preformed foam. This material is mixed to a specified density and pumped into any void. The fundamentals are simple, but the applications and the ability to mix properly and at high production rates can be challenging. The highly specialized equipment varies by contracting company. Each has spent years developing its own version of high-production equipment. The equipment cannot be purchased off the shelf and must be custom made. There is a network of foam manufacturers and highly trained specialty contractors throughout in the country to provide competitive pricing. In many areas of the country, state departments of transportation (DOTs) have developed standards

Large volumes in congested areas and difficult access are easy with cellular concrete. Shown is an 18-inch deep utility fill in San Francisco.

STRUCTURE magazine

What Is It and Why Would I Use It By Scott M. Taylor, P.E., MBA

Scott M. Taylor, P.E., MBA, is Vice President for Cell-Crete Corporation, managing the Engineered Fill department. He can be reached at staylor@cell-crete.com.

Lightweight foundation fills that are excavatable yet placed cost effectively and extremely fast.

for cellular concrete, and more are in development. Large agencies, such as the U.S. Army Corp of Engineers, Caltrans, Florida DOT and many large-scale builders are steady consumers of this product and proponents for its many uses. Many agencies and engineers are learning about the benefits, and the cellular concrete industry hopes the product will soon be a standard product in all 50 states. Cellular concrete can be provided at any density desired. As it gets heavier, it gets stronger but also more expensive. Your local provider is the best source for the determining the strength-to-weight relationship, as it varies a little with local cement quality and fly ash content. The standard cellular concrete mix weighs 30 pcf, with an average compressive strength of approximately 100 psi (14,400 psf ).

Where Does It Go and Why?

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Basically, cellular concrete can be pumped into any space. It is highly fluid and easily pumpable. This geotechnically strong,

Load balancing fills adjacent to existing structures do not cause adverse movement.

ultra-lightweight fill provides the following benefits to the structural engineer: 1) Lightweight fill in or below the structure 2) Zero lateral loading on adjacent walls, sheet piles or retaining structures 3) Long distance placement for tight locations 4) Extremely high bearing capacities 5) Insulation properties 6) Quick and easy void filling within the structure 7) Plaza fills at lower costs than those of other lightweight fills 8) Roof fills paired with expanded polystyrene (EPS) 9) Rat slabs

Why Would I Use Cellular Concrete on My Project?

Zero Lateral Loading Another standard use for cellular concrete is the “zero lateral load” concept. For a structure that requires exterior retaining walls, replacing some amount of heavy soil on the outside of the structure significantly reduces the lateral loading in the design. Cellular is placed in relatively shallow lifts, creating minor lateral fluid pressure for about 6 hours. After it hardens, the cohesion is so strong there is no lateral loading applied to the retaining structure. If there is no lateral loading, why does it need a retaining wall at all? A simple erosion face, is all that’s needed to protect the vertical face which is self-supporting. Rehabilitations and Metropolitan Work In rehabilitation work, there are often voids under slabs, behind walls, or in newly

The reason is simple: money!!! Basic economics require any new solution to be either better or more cost-effective than the current system. With cellular concrete, both may apply depending on the application. Here are a few examples: Building Support and Load Balancing What if you put the material under your building because you are concerned about the bearing capacity of the site soils or deep settlement? Placing cellular concrete in a uniform layer under the building provides a strong non-expansive base and reduces the overall weight of the new structure. Structural engineers then can revise the foundation system for this stronger, more stable, non-expansive subgrade. A win-win situation, especially in challenging site conditions such as those near waterfronts and over soft soils.

STRUCTURE magazine

December 2014

Cellular concrete flows into every nook and cranny with no vibration or placement effort.

continued on page 44

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constructed hidden areas. An example is buildings constructed in pits, which are then backfilled around each building after the below-grade portion is complete. Utility trenches also require backfilling, but the large numbers of pipes within a trench may pose a challenge for proper compaction. These areas can be filled with highly fluid cellular concrete at high-volume rates by running a hose to the location and pumping from the street. This method is relatively easy and clean (no wheelbarrows). The work above the fill can proceed the next work day.

Lightweight Plaza Fills Large structures are often designed to include roof gardens. To create the feel of a proper garden, the structure is built 4 feet below the finished grade to allow room for utilities and tree roots. This area is then filled with a lightweight material to provide subgrade for the surface slabs. Cellular Concrete is easy to apply in this situation as a poured-in-place product. There is no cutting required, and there is no concern about the shape/sloping of the structure. Nearly

the lightest of all fills, Cellular Concrete is simply the most cost effective solution. When designed for a mix design density of 25-27 pcf, the structural reinforcing rarely changes due to the weight of this fill over other alternatives. Hillside Residential Foundations: A Simpler Design For a new home to be built on a hill, a typical foundation design is to install deep piles typically spaced 8 feet apart. An alternative is excavating a trench at foundation lines down to bedrock and then backfill with cellular concrete. In some cases, savings of over 75% have been realized, with a dramatically more stable foundation system as it interlocks with the bedrock over larger areas. The foundation system should then be revised according to the new subgrade. Lightweight Insulated Concrete Roofs

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This long-standing hybrid system combines the high insulation value of Expanded PolyStyrene (EPS) with the strength of cellular concrete. In this system, an EPS tapered system is installed to create the insulation value then a 2-inch layer of 250 psi cellular concrete gives the roof the strong surface for the waterproofing layer to adhere. The savings starts in the ability to build the structure with a simple flat roof, and construct the slope-to-drain in the foam. Savings continue since EPS and Cellular are typically the least expensive insulation/sloping system. A very important long term benefit for the customer is that the insulation does not need to be replaced when reroofing the building.

Conclusions The various applications and benefits described above, as well as many others, are available to the knowledgeable structural engineer who has cellular concrete in his toolbox. This versatile, easy-toapply material is readily available from regional specialty contractors who can provide a wealth of knowledge, experience and design assistance.▪

Visit the new STRUCTURE website www.STRUCTUREmag.org

STRUCTURE magazine

December 2014

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

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

• Select the number of anchor points

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

• Predict mode of failure for anchor connections

• Model multiple edge and spacing distance configurations

• Recommend most efficient anchor size

• Calculate critical values for total strength design of anchor connections

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• Optimize designs across multiple scenarios. • Recommend most efficient anchoring method • Specify anchoring methods to achieve a desired failure mode

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InSIghtS

new trends, new techniques and current industry issues

Building Increased Productivity Using the Cloud By Sam Liu

n construction, time is money. And, when it comes to saving time and increasing productivity, the cloud is a catalyst for change. Arguably one of the most game-changing technologies of the century, the cloud to the computer industry is like utility grids for the power industry – a central fabric that powers the most complex computing tasks. However, it may be the simple things that result in the greatest business impact. Take, as an example, the access and sharing of important business documents and files. One of the most effective ways engineering firms can leverage the value of the cloud is to use it to share files. While it may sound like a simple task, sharing files can be one of the most tedious, time consuming drains on productivity in the construction industry. With the demand for mobility, the challenge of sending large files, the need to collaborate with external parties and the risk of version confusion and data loss, structural engineering firms have unique needs when it comes to file sharing.

Using the cloud to share files can give both productivity and power to the mobile worker. But, file sharing doesn’t only have to be used for files. Consider that there is a job change on site that demands quick action. By snapping a picture, or taking a video with a smartphone, workers can quickly convey a situation and its solution using the cloud. Using a sophisticated online file sharing solution, that photo can be easily shared with everyone involved for faster resolution. And, the photo and video files can be automatically archived and tracked for compliance and accountability. To best enable mobile collaboration, select a cloud file sharing solution that doesn’t restrict the device type which can be used. The best file sharing options support any mobile device and enable integrated document editing on tablets and mobile phones. This eliminates the need for additional and potentially cumbersome third-party mobile apps.

lead to unnecessary project slowdowns and cost overruns. By using a secure online file sharing solution, communication is streamlined and the turnaround time for project document modifications, reviews, and notifications can be shortened from hours and days down to minutes. When selecting a cloud file sharing solution that will empower your extended teams, be sure to select one that allows sharing with anyone, even if they are not a “member” of the file sharing service you use. The best solutions don’t require you to force your recipients to register or adopt a specific file sharing platform. They will offer access to shared files regardless of whether recipients are a registered user of that service or not, while still allowing the sender to remain in control of the document through access rights such as passwords and expirations.

Sharing Large Files

The Demands of Being Mobile

Large files present their own challenges. They are hard to email, time consuming to upload and challenging to manage. In the structural engineering field, this is particularly prevalent. The risk that part of an email attachment won’t be received can cause significant productivity impact, especially when sharing with vendors, partners or clients. With a secure online file sharing solution, site managers and subcontractors can easily and securely share vital files – no matter how large they are – without resorting to email or other unreliable systems. What’s more, new versions of files can automatically be tracked, updated and made available to all recipients.

When working on fast moving projects, data loss and breach are the last things a company wants to risk. In fact, data loss can not only be expensive, it can be devastating. According to market research firm Gartner Group, 43 percent of small businesses were immediately forced to close their business after experiencing a “major loss” of computer records. To be sure that your organization doesn’t become part of that 43 percent, look to a cloud file sharing solution that offers robust security features, including security audited geo-redundant data centers, data encryption, authentication technology, reliable data loss protection (DLP) and continuous monitoring against security risks. It is also wise to select a service that has received an independent SSAE 16 certification. Together, these multiple layers of security can safeguard your company data without the high costs and complexities of doing it yourself.▪

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Because building and engineering firms must work in a range of locations, from high-rises to remote areas, construction professionals are rarely in the office. Yet, regardless of where work is being done, access to files is paramount. Project documents such as design calculations, CAD drawings, reports, permits, and more need to be easily accessible both in the office and on the road. The easier and more ubiquitous the access, the more productivity can be achieved. ate or ce b a ll en co peri p x e velo de end att rn lea are sh eet m n joi

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Working with Extended Teams Compounding the need for simplified collaboration for professionals in the construction industry is the need to share content with multiple subcontractors, vendors, municipalities and clients that are outside the company firewall. Projects move fast; any miscommunication, lost document or a delay in response time can

STRUCTURE magazine

December 2014

Protecting Your Work

Sam Liu (sam@soonr.com), is the Vice President of marketing for Soonr (www.soonr.com) and an expert in mobile, cloud and enterprise technologies.

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CASE BuSinESS PrACtiCES

business issues

CASE on Contracts Part 1 By Steve Schaefer, P.E.

ood contracts are an important part of any structural engineering firm’s practice. Having a good contract can make your projects run more efficiently and improve your firm’s profits; conversely, an inappropriate or poorly written contract could be disastrous for your firm. This article is the first in a series of articles from CASE to help structural engineers have more profitable businesses by using contracts effectively.

The Basics What is a Contract? A contract is an agreement to do or not to do something. Saying that a contract is “valid” means it’s legally binding and enforceable. The point of a contract is to clearly outline an agreement so that the “object” is accomplished while preventing disputes that could lead to litigation. A lawsuit is a very inefficient and expensive way to resolve contract disputes; it also means you lose control over the issue being disputed since a judge or jury will be making the decisions instead. The essential parts of a valid contract include: • Parties. The contract must clearly identify the parties to the agreement. • Consent. A valid contract also requires the parties’ consent. Consent isn’t mutual unless the parties agree on the same thing in the same sense. This is often referred to as a “meeting of the minds”. Generally, there’s an offer and an acceptance communicated by the parties. • Object. The product or service being agreed to is also known as the object or subject. It must be lawful, possible and definite. For structural engineers, this is the “Scope of Services”. • Consideration. All contracts require consideration, meaning each party must gain something. Typically, your client gains your structural engineering expertise and your firm receives money in return; however, the consideration could also be free advertising, for example.

What Should a Good Engineering Services Contract Cover? In addition to the basic requirements, a good contract will provide additional protection by clearly documenting: a. When you will be paid. b. The consequences if you are not paid as required, such as being paid interest at the specified rate, allowing you to stop work on the project and/or forcing the client to reimburse you for legal expenses expended in order to collect the amount due. c. A detailed Scope of Services: i. Makes it clear what services you are providing. ii. Protects you from an expanded scope or scope creep by providing for extra compensation due to unforeseen circumstances or changes in the scope initiated by the client. iii. Protects you from claims regarding issues that were not within your scope of services. iv. In some cases, you may want to specify some services that you will not be providing. d. Other Terms and Conditions that are not the key elements of the contract but cover various situations that may occur. If a Contract Isn’t in Writing, is it Still Valid? Contracts do not have to be in writing. An oral contract is acceptable in many situations; however, there is no way to prove the terms of the agreement with an oral contract. In several states, a contract for engineering services must be in writing. Further, some states require a transaction over a certain dollar amount to be in writing. When the agreement doesn’t have to be in writing, all the other elements of a valid contract still have to be fulfilled.

before a contract is drawn up or signed, an attorney should review it; however, that can be expensive. Your professional liability insurance carrier probably provides a free contract review service, but this is usually only used for client-supplied contracts. You have other options available: The American Institute of Architects (AIA), the Engineers Joint Contract Documents Committee (EJCDC), the Council of American Structural Engineers (CASE), and others have written standard contracts for use in the architectural, engineering and construction fields. Contracts developed by these organizations cover typical conditions applicable to the members of their organizations and have been reviewed by attorneys. AIA and EJCDC have great contracts; however, AIA contracts are written to cover the work an architect will be providing to the owner, or the services that a sub-consultant will be providing to the architect. They are not written to address issues relative to the structural engineer. The EJCDC contracts are written to address large civil engineering projects. Neither organization has a good contract to cover structural engineering services for smaller projects with a limited scope. CASE has written over a dozen contracts specifically for structural engineers and the various situations they might encounter. By far the most widely used of these contracts is CASE Document 1, An Agreement for the Provisions of Limited Professional Services. This contract is in the form of a two-page Agreement and a one-page Terms and Conditions, and is intended to be used by structural engineers on investigations and small projects with a limited scope of services where the work will be performed within a relatively short time frame. As with all of the CASE contracts, it has been reviewed by attorneys experienced with structural engineering and construction litigation, and by Professional Liability Insurers.

Standard Contracts

Scope of Services

A well written contract is your best protection should a dispute arise. In a perfect world,

Even when using standard contracts, it is critical to specify an accurate and specific scope

STRUCTURE magazine

December 2014

Problems Caused By Poorly Defined Scope The intention of both the engineer and their client, a precast concrete supplier, was that the engineer would serve as a specialty engineer checking the reinforcing in the precast supplier’s proposed design, and modifying it where necessary so that it complied with the building code. Shortly after the precast was erected, non-structural cracks formed because of the way in which the precast supplier configured the structure. Because the engineer’s scope of services said “Design the precast structure” rather than the more specific “Review and modify the reinforcing in the precast supplier’s proposed design so that the precast concrete components complied with the building code”, the engineer and its professional liability insurer paid a very large claim for the expense of fixing the non-structural cracks.

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of services, and avoid language that would broaden your scope well beyond what you agreed to perform with the Client. Describe exactly what services you will be providing. For example, are you designing a repair to meet the current building code, a previous code or just to put a damaged structure back into its original condition (since that may be all that the client’s insurance company will pay for)? Since many projects are of a limited scope, you may be providing a lower level of service than on a large project; make sure that this is clear in the agreement. If necessary, note what services are not being provided. Some examples of exclusions or limitations are: 1) The preparation of a Construction Contract between the owner and contractor is not included. 2) The preparation or review of a construction cost estimate is not included. 3) Only one site observation visit during construction will be provided. It is good practice to offer providing these excluded services for an additional fee. Having an agreement that documents the additional services that were offered, but the client chose not to include, can reduce your liability if disputes arise.

Summary Although it may not be legally required, your contracts should be in writing and should cover the various conditions that may apply beyond the basics of Parties, Consent, Object and Consideration. Even when using a CASE or other organization’s standard contract, it is imperative that the scope clearly identifies what services you will and will not be providing. To help your firm use contracts more effectively, watch for these additional articles from CASE: • Terms and Conditions to be included in your contracts; • What new Project Managers need to know about contracts; • CASE’s survey of contract use; • How to respond to onerous clauses on Client supplied contracts.▪ Steve Schaefer, P.E., is the founder and chairman of Schaefer, a 60-person structural engineering firm, with offices in Cincinnati and Columbus, Ohio and is a member of CASE’s Programs Committee. Steve may be reached at steve.schaefer@schaefer-inc.com.

STRUCTURE magazine

December 2014

StruWare, Inc

Structural Engineering Software The easiest to use software for calculating wind, seismic, snow and other loadings for IBC, ASCE7, and all state codes based on these codes ($195.00). CMU or Tilt-up Concrete Walls with & without openings ($75.00). Floor Vibration for Steel Bms & Joists ($75.00). Concrete beams with/without torsion ($45.00). Demos at: www.struware.com

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A structural engineer agreed to check the proposed design for the contractor building the structural frame for an extreme sports event structure. The engineer’s contract said the engineer would “Analyze and design a temporary ramp structure” and that the engineer would “coordinate with (the event promoter and the ramp contractor)”. One of the athletes was seriously injured due to an error by the athlete compounded by a completely non-structural problem that developed during the competition. The athlete’s attorney used the usual “shot gun approach” and sued over twenty firms, any firm that was in anyway involved in the event. Because the judge interpreted the engineer’s term “ramp structure” to include all physical aspects for the event and not just the primary structural components, and assumed the engineer’s responsibility was to coordinate the entire event and not just the primary structural components, he did not agree to dismiss the engineer from the suit even though the structural components designed by the engineer performed perfectly. As a result, the engineer paid $25,000 in attorney fees plus $25,000 for a settlement since the cost to fight the suit would be considerably more than the settlement. If the engineer’s scope had been written to clearly say that the engineer was responsible only for the structural design of the primary structural components and to specifically list those components, the firm may have been dismissed from the suit, although they would have still had $25,000 in attorney fees.

CADRE Pro 6 for Windows

EARTH RETENTION GUIDE

news and information from earth retention companies

RetainPro Software

Software IES, Inc. Phone: 800-707-0816 Email: info@iesweb.com Web: www.iesweb.com Product: QuickRWall Description: That wall of earth won’t hold at all, it’s up to you: prevent its fall. Retain it fast with clear design, with Quick-R-Wall: nice bottom line!

Nemetschek Scia Phone: 410-290-5114 Email: info@scia-online.com Web: www.Nemetschek-Scia.com Product: Nemetschek Scia Description: Looking to migrate to, or improve your 3D design workflows? Scia Engineer can help. Tackle larger projects with advanced non-linear and dynamic analysis. Design to multiple codes, or script your own custom checks. Plug into BIM with IFC and links to Revit, Tekla and others. Download the FREE trial! All Resource Guide forms for the 2015 Editorial Calendar are now available on the website, www.STRUCTUREmag.org.

Phone: 800-422-2251 Email: info@retainpro.com Web: www.retainpro.com Product: RetainPro 10 Description: The leading earth retention design program for nearly 24 years. RetainPro 10 handles complete design for many different types of Retaining Walls: Cantilevered, Restrained, Tapered, Gravity, Gabion, Segmental with optional geogrids and solder pile. With thousands of uses nationwide, RetainPro is the defacto standard program for earth retention design.

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“The Wood Experts” Consultants in the Engineering Use of Wood & Wood-Base Composite Materials in Buildings & Structures • Product Evaluation & Failure Analysis • In-situ Evaluation of Wood Structures • Wood Deterioration Assessment • Mechanical & Physical Testing • Non-Destructive Evaluation • Expert Witness Services

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Attention Bentley Users Have you received your automatic quarterly invoice from Bentley?

Phone: 949-951-5815 Email: info@risa.com Web: www.risa.com Product: RISAFoundation Description: RISAFoundation is the ultimate tool for analysis and design of a variety of different foundation types. Featuring an open modeling environment, finite element analysis, and full integration with superstructure analysis programs; you won’t find a better choice for retaining wall, spread footing, combined footing, mat slab, or pile cap design.

Use SofTrack to control and manage Calendar Hour usage of your Bentley SELECT Open Trust Licensing. Call us today, 866 372 8991 or visit us www.softwaremetering.com

Phone: 203-421-4800 Email: info@s-frame.com Web: www.s-frame.com Product: S-CONCRETE Description: A concrete design industry standard, displays instantaneous results as you optimize and design reinforced concrete walls, beams and columns. Check thousands of concrete section designs in one run. With comprehensive ACI1 318-11 design code support, S-CONCRETE produces detailed reports that include clause references, intermediate results and diagrams. Product: S-FOUNDATION Description: Quickly design, analyze and detail your structure’s foundations with a complete foundation management solution. Run as a stand-alone application, or utilize S-FRAME Analysis’ powerful 2-way integration links for a detailed soil-structure interaction study. Automatically manages the meshed foundation model and includes powerful Revit and Tekla BIM links.

StructurePoint

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Phone: 847-966-4357 Email: info@structurepoint.org Web: www.StructurePoint.org Product: Reinforced Concrete Design Software Description: spWall is used for design and analysis of cast-in-place reinforced concrete walls, tilt-up walls, ICF walls, and precast architectural and load-bearing panels. spColumn is used for design of shear walls, bridge piers as well as typical framing elements in buildings and structures.

STRUCTURE magazine

Malcolm Drilling Co., Inc. Phone: 253-395-3300 Email: jstarcevich@malcolmdrilling.com Web: www.malcolmdrilling.com Product: Geotechnical Construction Description: The premier specialty contractor for earth retention systems and deep foundations, providing Design/Build solutions including secant pile walls, soldier pile walls, soilnailing, tiebacks, and ground improvement.

Suppliers

RISA Technologies

S-FRAME Software

Wood Advisory Services, Inc.

Speciality Contractors

December 2014

Gripple Inc. Phone: 630-406-0600 Email: e.balsamo@gripple.com Web: www.gripple.com Product: Ground Anchoring Solutions Description: Complete ground anchoring solutions for erosion control and slope stabilization. Provided in ready-to-use kits that include: Gripple Anchors, TerraLock terminations, and cable lengths specific to the job requirements and geotechnical conditions. Designed to save time and labor through easy and efficient installation.

Insulfoam Phone: 800-248-5995 Email: geofoam@insulfoam.com Web: www.insulfoam.com Product: InsulFoam® GF EPS Geofoam Description: Lightweight fill eliminates lateral loads on retaining walls. Replacing the active wedge with EPS geofoam, which can be free standing and selfsupporting, saves up to 75% of costs compared to traditional concrete walls designed to retain soil. For applications from large residences and commercial buildings to infrastructure.

VERSA-LOK Phone: 800-770-4525 Email: versalok@versa-lok.com Web: www.versa-lok.com Product: VERSA-LOK Standard Unit Description: VERSA-LOK Retaining Wall Systems have a solid construction and unique pinning system that enables unparalleled design flexibility. From erosion control and waterway installations to residential and commercial hardscapes. The Standard unit is available in traditional split-face or vintage weathered textures.

Williams Form Engineering Corp. Phone: 616-866-0815 Email: williams@williamsform.com Web: www.williamsform.com Product: Anchor Systems Description: Williams Form Engineering Corporation has been providing threaded steel bars and accessories for rock anchors, soil anchors, high capacity concrete anchors, micro piles, tie rods, tie backs, strand anchors, hollow bar anchors, post tensioning systems, and concrete forming hardware systems in the construction industry for over 90 years.

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StructurePoint’s suite of productivity tools are so easy to learn and simple to use that you’ll be able to start saving time and money almost immediately. And when you use StructurePoint software, you’re also taking advantage of the Portland Cement Association’s more than 90 years of experience, expertise, and technical support in concrete design and construction.

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GINEERS

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News form the National Council of Structural Engineers Associations

NATIONAL

22 Annual Conference nd

The 22nd Annual NCSEA Conference featured over three days of technical sessions, committee meetings, networking, business and fun, at the Astor Crowne Plaza Hotel in New Orleans. As Conference Chair, I would like to extend a heartfelt “thank you” to the Conference Committee, including Jamie Lorenz (MT), Emily Guglielmo (CA), Jera Schlotthauer (WY) and Tom DiBlasi (CT); NCSEA Board members Carrie Johnson, Chris Cerino and Ed Quesenberry; as well as NCSEA Staff members Jeanne Vogelzang, Susan Cross, Jan Diepstra and Melissa Matarrese; for assembling a wonderful slate of speakers. This was without a doubt one of the best conferences that we have held. Distinguishing this conference, we welcomed a record number of Young Members to the value that NCSEA provides for the practicing structural engineer. In keeping with NCSEA’s goal of catering to the practicing structural engineer, there was something for everyone. Noted leadership coach Kelly Riggs kicked off the conference with his thought provoking keynote address, “Why Your Strategic Plan is Doomed to Fail”. Kelly tied his keynote to the new strategic planning process currently being undertaken by NCSEA. Technical sessions ran the gamut from a preview of future changes to building codes and standards, to wind design for tornadoes, to sessions summarizing the most common errors with wind and seismic design and how to avoid them, just to name a few. The Annual Awards Banquet included recognition of the dedication of individual engineers to the structural engineering profession, and the Excellence in Structural Engineering Awards celebrated the structural engineering achievements, creativity and ingenuity of a variety of outstanding projects. We introduced eight Young Member Group scholarship winners at the Banquet and honored outstanding engineering service award recipients Jim Cagley, Jim Malley, Susan Jorgensen, Dustin Cole and Tim Mays. If you were unable to join us, the photos on this page will give you a snapshot of what you missed. Be sure to mark your calendars for the 23rd NCSEA Structural Engineering Summit which will take place in Las Vegas from September 30 – October 3, 2015.

The festive Opening Reception.

Young Member Conference Scholarship winners.

A friendly game of Jenga between sessions.

Outgoing President Carrie Johnson and incoming President Barry Arnold.

NCSEA News

– Ben Nelson, Conference Chair Mark your Calendars! 2015 NCSEA Structural Engineering Summit September 30 – October 3 Las Vegas Young engineer attendees at the Awards Reception.

NCSEA President Carrie Johnson presented the James Delahay Award to honorees Jim Cagley and Jim Malley.

STRUCTURE magazine

NCSEA Past Presidents.

December 2014

January 29–30, 2015

Hyatt Regency Coral Gables, Florida

Building Strategies for Growth & Success Platinum Sponsor APPROVE WITH CONFIDENCE

News from the National Council of Structural Engineers Associations

• How can engineering firms increase their value to clients? • How do you get your firm hired and retain relationship? • Should your firm grow organically or by acquisition? • What will your banker say? • What should you take into account when deciding whether or not to purchase another firm? These questions and more will be addressed at the 2015 Winter Leadership Forum in Coral Gables, Florida. Structural engineering leaders and firm principals will gather to discuss the issues confronting engineering firms in today’s environment. The Forum will feature roundtable discussions, presentations from firm principals and professionals in banking and finance, and a debate between structural engineering leaders on “How to Grow.” Registration is now open for the Forum, as well as hotel reservations at the Hyatt Regency Coral Gables, Florida. Register today at www.ncsea.com.

NCSEA News

2015 W

Look for the trusted marks and be confident that a product meets codes and standards requirements of Conformity!

www.icc-es.org 14-10383

2015 Structural Engineering Summit: Call for Abstracts Open Abstracts are now being received for 60-90 minute presentations at the 2015 NCSEA Structural Engineering Summit, September 30 – October 3 at Red Rock Resort in Las Vegas. The 2015 Summit will feature education specific to the practicing structural engineer, with potentially non-technical sessions as well.

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NCSEA

Diamond Reviewed

These courses will award 1.5 hours of continuing education. Approved for CE credit in all 50 States through the NCSEA Diamond Review Program. Time: 10:00 AM Pacific, 11:00 AM Mountain, 12:00 PM Central, 1:00 PM Eastern. NCSEA oﬀers three options for NCSEA webinar registration: Ala Carte, Flex-Plan, and Yearly Subscription. Visit www.ncsea.com for more information or call 312-649-4600.

Webinar Subscription Option!

December 2014

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Set up your 2015 continuing education now! NCSEA offers a Webinar Subscription Plan. For an annual fee of $750, an individual can access all NCSEA live webinars over a one-year period. This option is only open to NCSEA members, i.e., members of NCSEA MO’s, Aﬃliate, Associate and Sustaining Members. Enrollment form and details are available at www.ncsea.com.

ASS

STRUCTURE magazine

January 20, 2015 Design Examples using the ACI Anchorage Provisions Donald F. Meinheit, P.E., S.E., retired, Wiss, Janney, Elstner Associates

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January 13, 2015 Behavior, Design and Special Installation of Adhesive Anchors Donald F. Meinheit, P.E., S.E., retired, Wiss, Janney, Elstner Associates

January 6, 2015 Behavior and Design of Cast-in-Place and Mechanical Expansion Anchors Donald F. Meinheit, P.E., S.E., retired, Wiss, Janney, Elstner Associates

More detailed information on the webinars and a registration link can be found at www.ncsea.com.

NCSEA Webinars

Abstract session proposals of up to 500 words must be received by February 23, 2015. Presenters of accepted abstracts will be notified by March 16, 2015. Speakers will be provided with required guidelines after acceptance of abstract. More information can be found at www.ncsea.com.

COUNCI L

Structural Columns

The Newsletter of the Structural Engineering Institute of ASCE

Registration Now Open for Structures Congress 2015 New ideas. New practices. New science. New resources. New colleagues. April 23–25, 2015 Portland, Oregon “The sessions I attended were informative but the opportunity to speak with the leaders in our profession is what keeps me coming back.” TOP REASONS TO ATTEND • Network with researchers, designers, project/construction managers, and contractors from around the world to discuss current and future challenges for structures • Gain knowledge by attending outstanding technical sessions – over 110 from which to choose • Visit a wide range of exhibitors in one location and find the latest tools to help your organization • Earn Professional Development Hours (PDHs) in technical sessions to maintain your professional licensure • Attend the opening and closing plenary sessions to hear compelling presentations by innovative top leaders in the field

• Interface with students and young professionals • Visit Portland for roses, parks, museums, outdoor adventures, great food, microbreweries, and so much more • Enjoy learning & earning PDHs from the Council of American Structural Engineers (CASE) at their Spring Risk Management Convocation Visit the congress website at www.structurescongress.org for more information and to register.

Call for Abstract and Session Proposals Now Open We are seeking dynamic sessions and presentations on topics addressing both Geotechnical and Structural Engineering issues. Final papers are optional and will not be peer reviewed. Consider submitting either session proposals or single abstracts related to the topics and subtopics of interest to both professions. The 2016 joint congress will feature a total of 15 concurrent tracks: there will be tracks based on traditional GI and SEI

topics, and tracks on joint topics. In addition, we will be offering interactive poster presentations within these tracks. All proposals must be submitted by April 7, 2015 (no extensions). Visit the joint conference website at www.Geo-Structures.org for more information and to submit your abstract.

Thank you to 2014 SEI Sustaining Organization Members:

Second ATC-SEI Conference

Improving the Seismic Performance of Existing Buildings and Other Structures December 10–12, 2015 Hyatt Regency San Francisco

Become an SEI Sustaining Organization Member Raise recognition for your organization in the structural engineering community, and increase visibility to more than 25,000 SEI members via the SEI website, SEI Update e-newsletter, and SEI’s Structural Columns in STRUCTURE magazine. Learn more at www.asce.org/SEI. STRUCTURE magazine

Call for abstracts and session proposals now open! Organized by the Applied Technology Council (ATC) and the Structural Engineering Institute (SEI) of the American Society of Civil Engineers (ASCE), this conference will be dedicated to improving the seismic performance of existing buildings and other structures. All proposals must be submitted by January 22, 2015 (no extensions). See the conference website at www.atc-sei.org/ for more information and to submit your abstract.

December 2014

New Committee on Advances in Information Technology

Ashraf Habibullah, structural engineer and Founder, President, and CEO of Computers and Structures, Inc., is offering a generous matching gift challenge to support the SEI Futures Fund. He will match, dollar for dollar, any new donations made by SEAOC members to the SEI Futures Fund by December 31, up to $25,000. Your gift, combined with Ashraf ’s, could total $50,000 in vital program funding for the Futures Fund, which invests in activities that advance the art, science and practice of structural engineering. Learn more about strategic efforts the SEI Futures Fund supports, and give today at www.asce.org/SEI.

SEI has created a new technical committee on Advances in Information Technology. The new committee will reside in the Analysis and Computation TAC. Chaired by Ronald T. Eguchi of ImageCat, Inc., the committee will focus on how emerging technologies can be used for structural design and analysis, post-disaster response and recovery, and pre-event planning and disaster preparedness. The committee will seek to bring together technologists and practicing engineers to bridge the gap between product idealization and implementation. See the SEI website at www.asce.org\SEI to learn more.

2015 ASCE Bridge Calendar Now Available

Promote your Business All Year Long Print your company name and logo across the full 12-inch width at the bottom of customized Bridges 2015 calendars. Your brand and message will be in front of your clients and colleagues every day. For additional questions about calendar advertising, contact ASCE at pubsful@asce.org.

Enter the 2015 SEI Student Structural Design Competition Deadline is January 5, 2015

Gain valuable professional and networking experience, compete for cash prizes, and raise visibility for your team and university. Awards include complimentary registration, sponsored by the SEI Futures Fund, to participate and present finalist projects at Structures Congress April 23–25, 2015 in Portland, Oregon. Visit the SEI website at www.asce.org/SEI to learn more and to enter.

Box Girders Survey

Professional Interest Inventory

The Seattle team of Parsons Brinckerhoff is developing an independent research project on the prestressed-concrete boxgirder bridges constructed in the past 20 years in the U.S. and internationally. The project includes creating a bridge database and analyzing the impacts of different construction methods on deck dimensions and quantities of concrete, mild reinforcement and post-tensioning. If interested in participating in this research, please contact Marco Rosignoli at atrosignolim@pbworld.com or Joan Zhong Brisbois at zhong@pbworld.com. A form will be distributed to collect a few project specifics – bridge geometry, construction method, moment of inertia and quantities of materials. The results of the research will be published.

Complete ASCE’s online Professional Interest Inventory. The PII will give ASCE the ability to tailor its email marketing to send you only the items that are relevant to you. The PII allows you to select specific topics such as Bridges, Buildings, and Electrical Transmission Structures. This will help ASCE avoid sending messages that don’t interest you. It takes less than five minutes. To complete your PII, log in to your ASCE account at www.asce.org/interests, check off your preferences and submit.

STRUCTURE magazine

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

December 2014

The Newsletter of the Structural Engineering Institute of ASCE

Bridges 2015 offers spectacular images of bridges from the United States and around the world. This calendar is a celebration of the unique blend of technology and art that is the hallmark of great engineering. Every photo in the calendar was selected from entries to ASCE’s Bridges Photo Contest. The photos selected for the 2015 calendar celebrate the form, function, and style central to excellence in civil engineering. Visit the ASCE website at www.asce.org to order your calendar today.

Structural Columns

SEI Futures Fund SEAOC Matching Challenge

CASE in Point

The Newsletter of the Council of American Structural Engineers

CASE Contracts – Now Available! CASE #1 – An Agreement For the Provision of Limited Professional Services BEST SELLER!! This is a sample agreement for small projects or investigations of limited scope and time duration. It contains the essentials of a good agreement including scope of services, fee arrangement, and terms and conditions. CASE #2 – An Agreement Between Client and Structural Engineer of Record for Professional Services BEST SELLER!! This agreement form may be used when the client, e.g. owner, contractor developer, etc., wishes to retain the Structural Engineer of Record directly. The contract contains an easy to understand matrix of services that will simplify the “what’s included and what’s not” questions during negotiations with a prospective client. This agreement may also be used with a client who is an architect when the architect-owner agreement is not an AIA agreement. CASE #3 – An Agreement Between Structural Engineer of Record and Consulting Design Professional for Services The Structural Engineer of Record, when serving in the role of Prime Design Professional or as a Consultant, may find it necessary to retain the services of a sub-consultant or architect. This agreement provides a form that outlines the services and requirements in a matrix so that the services of the subconsultant may be readily defined and understood.

CASE #4 – An Agreement Between Owner and Structural Engineer for Special Inspection Services Special Inspection services provided by a Structural Engineer are normally contracted directly by the Owner of a project during the construction phase. This agreement has a Scope of Service that directly relates to the applicable code or industry standard requirements. The Structural Engineer of Record or another structural engineer providing these services may use this agreement. The language for coordinating laboratory testing work is also included within this agreement. CASE #5 – An Agreement for Structural Peer Review Services A request to perform a peer review of another structural engineer’s design brings with it a different responsibility than that of the Structural Engineer of Record. The CASE #5 document addresses the responsibilities and the limitations of performing a peer review. This service is typically performed for an Owner, but may be altered to provide peer review services to others. These publications, along with other CASE documents, are available for purchase at www.booksforengineers.com.

Donate to the CASE Scholarship Fund! The ACEC Council of American Structural Engineers (CASE) is currently seeking contributions to help make the structural engineering scholarship program a success. The CASE scholarship, administered by the ACEC College of Fellows, is awarded to a student seeking a Bachelor’s degree, at a minimum, in an ABET-accredited engineering program. We have all witnessed the stiff competition from other disciplines and professions eager to obtain the best and brightest young talent from a dwindling pool of engineering graduates. One way to enhance the ability of students in pursuing their dreams to become professional engineers is to offer incentives in educational support. In addition, the CASE scholarship offers an excellent opportunity for your firm to recommend eligible candidates for our scholarship. If your firm already has a scholarship program, remember that potential candidates can also apply for the CASE Scholarship or any other ACEC scholarship currently available. Your monetary support is vital in helping CASE and ACEC increase scholarships to those students who are the future of our industry. All donations toward the program may be eligible for tax deduction and you don’t have to be an ACEC member to donate! Contact Heather Talbert at htalbert@acec.org to donate. STRUCTURE magazine

Follow ACEC Coalitions on Twitter – @ACECCoalitions. December 2014

Does your company have data but lack insight? Is the rapid pace of change a challenge to timely decision-making? Is valuable time wasted searching for just one more piece of data? As a leader of a small firm, you face increasingly complex decisions – decisions that are filled with ambiguity, uncertainty and risk. To remain competitive, you can’t wait for complete data and certainty. To save time and money, you must decide and decide now. It’s easy. Successful leaders know the secret. They gather as much information as feasible and they pay attention to intuition – gut feel. Powerful decisions come from balancing cognition and intuition in a skilled internal calculus. New research in neuroscience reveals the proven processes your brain uses to perform that calculus. Now you can harness that power for the management of your firm and development of future leaders.

Through these sessions, discover practical skills that put neuroscience to work for you and your business so that you can: avoid the pitfalls of over-thinking; sidestep analysis paralysis; learn techniques to simplify complex decisions; and develop future leaders who are both smart and insightful. Increase your decision-making skills now at ACEC’s Small Firm Council’s (SFC) annual Winter Meeting February 20-21 in Nashville. Speaker, Coach and Author, Shelley Row, P.E., of Shelley Row Associates LLC, will ignite an interactive exploration of complex decision-making based on her personal interviews with over 70 leaders. The data confirms that the most effective leaders make decisions by gathering information while trusting their intuition. That remarkable combination is what Shelley calls infotuition™. Don’t over-think it! Join the discussion today. Infotuition™…You’ve got it. Are you using it? To register, visit www.acec.org/coalitions.

NEW AMAZON PORTAL Knowledge is power – and your firm’s greatest asset. Whether it’s keeping ahead of the competition or improving your bottomline, beefing up your firm’s know-how can only help. And laying your hands on trustworthy A/E and business resources is about to become a whole lot easier. In mid-August, ACEC launched its new webstore, the ACEC Business Resource Center, on the Amazon e-commerce platform. Now ACEC members, as well as A/E professionals worldwide,

can enjoy fast access to hundreds of engineering and general business resources, published by ACEC and other publishers, through one convenient hub. As an added benefit, current Amazon Prime members can continue to enjoy the privileges of Prime membership – including free 2-day shipping – when making purchases at the ACEC Business Resource Center. Visit the ACEC Business Resource Center at www.ACECEngineeringBookCenter.org.

CASE Risk Management Convocation in Portland, OR The CASE Risk Management Convocation will be held in conjunction with the Structures Congress at the Doubletree by Hilton Downtown Hotel and Oregon Convention Center in Portland, OR, April 23-25, 2015. For more information and updates go to www.seinstitute.org.

The following CASE Convocation sessions are scheduled to take place on Friday, April 24: 7:00 AM – 8:15 AM CASE Breakfast: The Future of Structural Engineering Sue Yoakum, Donovan Hatem 8:30 AM – 10:00 AM Addressing Hidden Risks in Today’s Design Contracts Speakers – Rob Hughes, Ames & Gough; Brian Stewart, Collins, Collins, Muir & Stewart 10:30 AM – 12 Noon How to Succeed Without Risking It All! Moderator – John DalPino, Degenkolb Engineers 1:30 PM – 3:00 PM Lessons Learned From Structural Cases in Litigation Speaker – Jeffrey Coleman, The Coleman Law Firm 3:30 PM – 5:00 PM SE Practice for Quality and Profitability – Panel Discussion Moderator – Stacy Bartoletti, Degenkolb Engineers

STRUCTURE magazine

December 2014

CASE is a part of the American Council of Engineering Companies

ACEC Business Insights

CASE in Point

Strengthen your Competitive Edge: Increase your Decision-Making Skills

Structural Forum

opinions on topics of current importance to structural engineers

Rethinking Engineering Licensure By Kip Gatto, P.E., S.E.

t was a pleasure to read the 2013 report by the SEI Board of Governors Task Committee, A Vision for the Future of Structural Engineering and Structural Engineers: A Case for Change. This document provides great suggestions for significant changes in the profession if structural engineers are to remain a respected and vibrant part of the global community. Advancements in technology and ongoing globalization require reappraising the structural engineer’s role in the design, development, and preservation of the built environment. Although technical abilities remain important, other skills –leadership, innovation, diversity, and economics – now need to be considered of near-equal importance. Excessive risk aversion and over-reliance on prescriptive design criteria are hindering progress. Most of us who practice structural engineering are constantly reminded by our well-meaning colleagues about “liability” and are directed to an alphabet soup of codes and standards that constrain our innovations. The values espoused in the SEI document seek to restrain this tendency and pose refreshing goals for the future of our profession. The SEI committee recommends substantive changes in the way we educate new engineers, conduct business, and define our profession, all of which are clearly consistent with their stated goals. They also endorse the promotion of “structural engineering licensure …. needed to promote public safety in the built environment.” It is not as clear how this recommendation is consistent with their objectives. It feels to some like an attempt to restrain trade and legislate our way around the reality that automated design and specialty engineering are causing part of our profession to become obsolete. Although there have been some dramatic cases of design errors causing tragic loss of life and property, such as the Hyatt Regency in Kansas City and the I-35W Bridge in Minneapolis, many remain skeptical that licensure laws would have prevented these tragedies or will substantially contribute to safer structures in the future. Attributes such as innovation, leadership, and diversity are not well-captured in the

licensing process, implying that these “softer” skills are not as important to our profession. We are competing for candidates with other exciting disciplines that embrace these skills for designing cars, biomedical machines, spaceships, supercomputers, solar panels, and other fascinating and useful technologies for the global community. These thriving disciplines do not typically rely on licensure for furthering their profession or providing safe work products. To some extent, structural licensure actually has the potential to lead to complacency, implicitly relieving some licensed individuals from their duty to be innovative leaders and stay up-todate. Proposed solutions to this generally acknowledged issue typically include even greater reliance on bureaucratic processes, which seem just as attractive to us as codifying every aspect of engineering design. Structural licensure has been adopted in many states and is likely to be adopted in even more. The train has already left the station, so to speak. Assuming that this train will not be stopped, a logical analysis suggests that instead of resisting it, those with concerns may be better served by trying to redirect it. SEI identifies one indicator that its vision for the future is being realized as when “Earning a structural engineering license is viewed as a major achievement and aspirants would willingly rise to the challenge to earn the distinction.” It might be time to rethink what the challenge is so that the process of earning a license can be made more consistent with SEI’s stated objectives and can thus attract more dynamic and diverse candidates. Most engineers familiar with the licensing exam are aware that its primary goal is to evaluate a candidate’s ability to apply building and bridge codes properly to structural engineering design. If you do not have a good understanding of the codes, you are not going to pass the exam. Although this may seem like a sensible goal, it is actually inconsistent with the vision of SEI, which indicates that a heavy reliance on codes is not necessarily desirable for the future of the profession. Could we not instead encourage

up-and-coming engineers to focus their efforts on mastery of the fundamentals – such as Newtonian mechanics, material behavior, and structural response – rather than current code provisions? The code will be at least somewhat different three years from now, and substantially different 30 years from now, but proper application of engineering principles will result in safe structures in perpetuity. Consider (what should be) the simple design of a cast-in-place concrete anchor. Instead of requiring candidates to demonstrate that they can quickly navigate all 48 pages of ACI 318 Appendix D, would it not be better to have them instead demonstrate ability to calculate anchor strength from first principles such as failure cone geometry and concrete tensile strength? Have them recommend a factor of safety for the anchor design and justify it based on the expected reliability of the anchor. Or consider the calculation of seismic forces on a structure. Instead of requiring candidates to determine code values for various parameters and apply prescribed force distribution equations, they could be provided with an arbitrary response spectrum and be required to estimate the spectral acceleration based on the calculated period of the structure. They could then be asked to estimate an appropriate force reduction based on overstrength, ductility, etc. (not tables), and distribute calculated forces based on seismic principles. Consideration should also be given to exam questions that test for “softer” skills. Candidates could be presented with a scenario that includes economic and cultural sensitivities, and then asked how they would handle the situation. A rethinking of licensure priorities along these lines could help the process appeal to a broader group, require genuine demonstration of competence, and attract dynamic candidates with a desire to rise to the challenge.▪ Kip Gatto, P.E., S.E. (kgatto@wje.com), is an Associate Principal with Wiss, Janney, Elstner Associates, Inc. in Seattle, Washington.

Structural Forum is intended to stimulate thoughtful dialogue and debate among structural engineers and other participants in the design and construction process. Any opinions expressed in Structural Forum are those of the author(s) and do not necessarily reflect the views of NCSEA, CASE, SEI, C 3 Ink, or the STRUCTURE® magazine Editorial Board. STRUCTURE magazine

December 2014

Strong Structures Come From Strong Designs

With RAM™, STAAD® and ProStructures, Bentley offers proven applications for:

Build it with Bentley! Integrated projects, teams and software. Bentley’s Structural Software provides you the tools you need for strong designs and supports an integrated workflow all the way around. Having all the applications you need for the tasks at hand, along with the ability to easily synchronize your work with the rest of the project team, helps you get your job done right, fast and profitably.

Visit www.bentley.com/Structural to learn more! © 2014 Bentley Systems, Incorporated. Bentley, the “B” Bentley logo, ProjectWise and MicroStation are either registered or unregistered trademarks or service marks of Bentley Systems, Incorporated or one of its direct or indirect wholly owned subsidiaries. Other brands and product names are trademarks of their respective owners.

• Metal Buildings • Steel/Steel Composite • Aluminum • Reinforced Concrete • Foundation Design • Steel Connections • Structural Drawings and Details

… all easily coordinated with the Architect and other team members and their design applications – such as AutoCAD, Revit, MicroStation® and more.

STRUCTURE magazine | December 2014

Articles inside

Structural Rehabilitation

InSights

Structural Forum

Building Blocks

Structural Design