Design for Lateral Loads/Systems

Single Abstract

343359 - New Studies to Assess and Improve Seismic Torsion Design Provisions

Friday, April 20
11:00 AM - 12:30 PM
Location: 204AB

This study evaluates ASCE/SEI 7 design requirements for seismic-induced torsion in buildings, using collapse resistance as the primary metric. Two of the main objectives of the study are to: (1) determine the effectiveness of ASCE/SEI 7 torsion design requirements for preventing seismic-induced collapse of torsionally irregular buildings, (2) propose modifications to ASCE/SEI 7 torsion design requirements to eliminate deficiencies and/or unnecessary sources conservatism.

The study finds that ASCE/SEI 7 torsion design provisions are generally conservative for most building configurations—exceptions are some buildings that rely heavily on lines of lateral resistance orthogonal to the design earthquake force to resist torsion moments. It is also observed that the ASCE/SEI 7 requirements that drift and stability limits are satisfied at the building edge are important for ensuring that torsionally sensitive buildings have adequate collapse resistance.

Based on preliminary findings, the following modifications to ASCE/SEI 7 would provide better consistency in collapse resistance over a large range of building configurations and degrees of torsional irregularity: (1) altering the triggers for requiring a redundancy factor of 1.3 so that fewer buildings are affected, (2) considering the effects of the orthogonal ground motion component for computing torsion moments in buildings classified as extremely torsionally irregular, (3) reducing the accidental torsion amplification factor.

Furthermore, the study demonstrates that buildings classified as extremely torsionally irregular need not be banned from Seismic Design Categories E and F, as long as the lateral system is proportioned properly; neither should the equivalent lateral force procedure be prohibited on the basis of torsional irregularity.

This study is of national significance, as it is anticipated to directly affect future editions of ASCE/SEI 7. The content of this study is of interest to building code developers, engineers who use ASCE/SEI 7 or codes that reference it, and earthquake engineering researchers. The audience will take away the following: (1) a better understanding of how torsion design provisions in ASCE/SEI 7-16 affect building collapse resistance, including when they are conservative vs. unconservative, (2) design strategies for obtaining more consistent performance among torsionally regular and irregular buildings, (3) insight into potential revisions of future editions of ASCE/SEI 7 and their technical basis.

The study is part of a project managed by the Applied Technology Council (ATC) under FEMA contract HSFE60-12-D-0242 task order HSFE60-16-J-0223, entitled “ATC-123: Improving Seismic Design of Buildings with Configuration Irregularities.” Any opinions are those of the authors and not necessarily ATC or FEMA.

David (Jared) DeBock

Assistant Professor
California State University, Chico

David (Jared) DeBock is an assistant professor of Civil Engineering at California State University, Chico. Prior to joining CSU Chico, Jared earned his PhD at CU Boulder and worked as an engineer at J.R. Harris and Company Structural Engineers in Denver. Jared’s research experiences include performance-based earthquake engineering, risk assessment for individual buildings as well as collections of spatially distributed buildings, nonlinear modeling, structural reliability, snow loading, and building codes and standards.

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Dustin Cook

Research Engineer
Haselton Baker Risk Group

Dustin has served as a technical product developer and a research engineer for Haselton Baker Risk Group since 2014. At the Haselton Baker Risk Group he has been a technical working member on several ATC and NSF projects, authored papers for SEAOC and ATC conferences, and helped develop and produce the Seismic Performance Prediction Tool (SP3). Dustin earned his M.S. in Civil Engineering from the University of California, Los Angeles in June of 2014 and received his PE license in the spring of 2017.

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Katie Wade

Research Engineer
Haselton Baker Risk Group

Katie has served as a research engineer for Haselton Baker Risk Group as well as a research assistant for the Haselton Research Group since 2014. During this time she has participated in implementing the Seismic Performance Prediction Program (SP3), consulted on seismic loss assessments for a number of new design and existing buildings, and contributed to several ATC and NSF projects. Katie earned her BS in Civil Engineering from California State University, Chico and her MS in Structural Engineering from Stanford University.

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Curt Haselton

CEO
Haselton Baker Risk Group

Curt is a leader in the field of structural earthquake engineering, with recent work focusing on building code development, building collapse safety assessments, and earthquake damage and loss estimation. In addition to his role as Co-Founder and CEO of HB Risk, he is a Professor in Civil Engineering at California State University, Chico. He received his Ph.D. in Structural Engineering from Stanford University in 2006. Among his awards, Curt received the 2013 Shah Family Innovation Prize from the Earthquake Engineering Research Institute, honoring an individual under the age of 35 for creativity, innovation and an entrepreneurial spirit in earthquake risk mitigation and management.

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Mike Valley

Principal
Magnusson Klemencic Associates, Inc.

Over the last 29 years, Mike has managed many large, complex projects involving both new construction and renovation. He brings special expertise in seismic and foundation analysis and design, and he has been a key participant in the U.S. development of performance-based seismic design approaches. Mike frequently serves on committees and advisory panels charged with the development and authoring of national engineering codes and standards, including those for FEMA, NEHRP, and the Building Seismic Safety Council. His expertise and contributions have been recognized with an “Engineer of the Year” award from the Structural Engineers Association of Washington and a James M. Delahay Award from the National Council of Structural Engineers Association. Mike also leads MKA's Earthquake Technical Specialist Team and will bring an enhanced understanding of state-of-the-art approaches.

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