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Tall Buildings Initiative - Tasks

Task 1 - Establish and Operate the Tall Buildings Project Advisory Committee (T-PAC)

Task description – Select members for the T-PAC, including experts and representatives from the seismology, geotechnical engineering, structural engineering, and building regulation communities. Convene the T-PAC to initiate the project, define operating procedures, and advise on scope, tasks, and investigators. Meet on a regular basis to review ongoing work and recommend revisions in tasks as well as recommend new tasks. Seek expanded participation and funding as appropriate. Serve as an overall project quality control board, ensuring that main findings of this project have achieved consensus of the T-PAC prior to release.

Lead investigator – Jack Moehle

Team members – In addition to the lead investigator;

• - Yousef Bozorgnia (Project Manager, PEER);
• - Paul Somerville (SCEC);
• - Marshall Lew (LATBSDC);
• - Mark Moore (SEAOC);
• - Ray Lui (SFDBI);
• - Norm Abrahamson, Ron Hamburger, Helmut Krawinkler, and Farzad Naeim (experts at large)

Task 2 - Develop consensus on performance objectives

Task description – Using an appropriate methodology, develop a consensus on performance objectives. Some emphasis on residential construction, i.e., condominiums, but including other occupancies. Document methodology and performance objectives in a final report. Basic performance objective to be the minimum performance specified in the building code, but this project has an assignment of defining specifically what that performance objective is. Considered performance objectives should include conventional performance objectives and alternative ways of expressing objectives. Alternative performance considerations may include reparability and reoccupancy. Final objectives should clearly define confidence levels associated with objectives. An analysis of socio-economic impacts associated with tall building performance should be considered.

Lead investigator – Bill Holmes

Team members – Charlie Kircher, Laurence Kornfield, Bill Petak, and Nabih Yousef, plus contributions from position paper writers and workshop attendees as appropriate.

Task 3 – Assessment of ground motion selection and modification procedures

Task description – Conduct analyses of multistory building models subjected to a large number of earthquake ground motions to determine the native statistics of the responses, compare results with results obtained using various proposed ground motion selection and modification procedures, and recommend appropriate ground motion selection and scaling procedures. Document methodology and results in final report. Work to be conducted in coordination with the PEER working group on ground motion selection and scaling. Buildings models to include two core wall models (of different heights) and two frame models (of different heights). Building models preferably based on actual building projects, preferably the models (slightly modified) from the actual projects. Collect statistics on important design parameters including roof drift, interstory drift, floor accelerations, moment profiles, shear profiles, collector forces, etc. Identify ground motion parameters that correlate best with response quantities. Recommend selection and scaling procedures for design.

Lead investigator – Jack Moehle

Team members – John Hooper, Stephen Mahin, two research assistants

Task 4 - Synthetically generated ground motions

Task description – Using validated broadband ground motion simulation procedures, generate ground motion time histories in San Francisco and Los Angeles for large earthquakes on the major faults in the region. The time histories will be simulated for geographic areas of specific interest for San Francisco and Los Angeles. These broadband simulated time histories are to contain long period effects such as rupture directivity effects and basin effects that are specific to the fault geometry and geological structure of the regions.

Lead investigator – Paul Somerville

Team members – Brad Aagaard, N. Collins, Rob Graves

Task 5 – Review and validation of synthetically generated ground motions

Task description – Conduct review of procedures and results obtained in Task 4, with purpose of establishing a validated reference set of synthetically generated broadband ground motions. Work closely with researchers in Task 4 to ensure the final results are based on the best available technologies and assumptions, and are properly interpreted. Develop final report documenting procedures used to generate motions as well as validation procedures. Provide digital set of validated synthetic ground motions.

Lead investigators – Farzad Naeim and Yousef Bozorgnia

Team members – N. Abrahamson, B. Chiou, CB Crouse, D. Dreger, J. Hooper, N. Luco, J. Maffei, Y. Moriwaki, Y. Zeng

Task 6 - Guidelines on selection and modification of ground motions for design

Task description – Using findings from Tasks 3 through 5, write guidelines for selection and modification of ground motions for design of tall buildings. Apply recommendations to virtual sites in San Francisco and Los Angeles to demonstrate procedures and to establish a sample set of validated ground motions that can be used in subsequent research or for design of tall buildings.

Lead investigators – Yousef Bozorgnia and Nico Luco

Team members – Farzad Naeim, John Hooper, Norm Abrahamson, Joe Maffei

Task 7 - Guidelines on modeling and acceptance values

Task description – Develop practical guidance for nonlinear modeling of tall buildings in reinforced concrete (priority), steel, and composite construction. Conduct workshop to identify critical issues in tall buildings modeling and acceptance values, rather than covering the entire field. Identify researcher/practitioner teams to review the literature and conducted limited analyses to identify appropriate procedures. Methodology and findings to be documented in final report. Include recommendations for stiffness, strength, deformation capacity, hysteretic models, and implementation in software for nonlinear dynamic analysis. Provide guidance on appropriate use of overstrength parameters, capacity reduction parameters, etc. for capacity design. Work with experienced consultants to ensure focus on key components and systems that affect earthquake response and design, including modeling of podium force transfer. As appropriate, conduct analyses to validate procedures.

Lead investigator – James Malley

Team members – Greg Deierlein, Helmut Krawinkler, Joe Maffei, Mehran Pourzanjani, John Wallace, and others as needed.

Task 8 – Input ground motions for tall buildings with subterranean levels

Task description – Prepare interim report describing the state of the art and practice for definition and input of ground motions for tall buildings with embedded foundations. Define additional needed studies as appropriate. Rely on past analytical and empirical studies. Work with experienced engineers familiar with tall building configurations and analysis procedures. Also, identify any other major issues to be investigated for foundation design of tall buildings.

Lead investigator – Jon Stewart

Team members – C.B. Crouse, M. Lew, F. Ostadaan, E. Taciroglu, and structural engineer to be determined.

Task 9 – Presentations at conferences, workshops, seminars

Task description – Implement a vigorous outreach program to engage a broad group of stakeholders and end users in the program, so it is well known among key stakeholders and end users, and so it is aware of and responsive to needs of those stakeholders and end users.

Lead investigator – Jack Moehle

Proposed team members – T-PAC