Dynamic Analysis Procedures for Performance-based Seismic Engineering of Unsymmetric-plan Buildings

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

While nonlinear response history analysis (RHA) is the most rigorous procedure to estimate seismic demands for buildings, it remains impractical for widespread use by the profession. This is especially true for unsymmetric-plan buildings, which require three-dimensional analysis to account for coupling between lateral and torsional motions. Before nonlinear RHA can become a standard tool in structural engineering practice, commercial software must become more robust, reliable, and convenient for structural modeling, input data preparation, and interpretation of response results. The overall objective of this research proposal is to explore the possibility of developing an analytical procedure to estimate seismic demands for unsymmetric-plan buildings. This method must be sufficiently accurate and reliable for performance-based seismic engineering, but at the same time, it should not be so complicated that it is impractical for use by the profession. The challenge then is to develop a simplified method based on structural dynamics theory for nonlinear seismic demand analysis of buildings. A Small Grant for Exploratory Research (SGER) would provide an opportunity to explore the several conceptual issues that must be resolved before meeting this challenge. These issues include: coupling of x-lateral, y-lateral, and torsional motions of unsymmetric-plan buildings, and simultaneous action of two horizontal components of ground motion. The proposed research program will provide an opportunity to explore the feasibility of developing dynamic analysis procedures for performance-based seismic engineering of unsymmetric-plan buildings, considering various types of ground motions, including near-fault ground motions. The challenge is to develop a simplified method simpler than rigorous nonlinear RHA, rooted in structural dynamics theory for nonlinear seismic demand analysis of buildings. The method should be designed to work directly with the earthquake design spectrum, which is the standard approach to defining seismic hazard. If this exploratory research leads to promising results, it will provide the foundation for developing a novel procedure that is expected to be much superior than existing methods. Intellectual Merit: Based on structural dynamics theory, the MPA procedure has the potential to be a major improvement over other existing simplified methods for estimating seismic demands on buildings and other structures. It could provide a unified analytical formulation for tackling two- or .three- dimensional analysis of buildings for any type of excitation, near-fault or far-fault. Concepts underlying the MPA may be applicable to other classes of structures, e.g., bridges, intake-outlet towers, etc. The MPA procedure thus may open the door for research aimed at systematically developing approximate but rational methods for estimating the seismic demands for different classes of structures, recognizing their vibration properties. Broader Impact: This collaborative research program between Anil K. Chopra at the University of California, Berkeley, a major research institution, and Rakesh K. Goel at the California Polytechnic State University, San Luis Obispo, a primarily undergraduate university, could also lead to significant broader impacts, including integration of research into graduate and undergraduate education; increased participation of under-represented groups; broad dissemination of results to educators, researchers, engineers, and code-writing professionals; as well as integration of diversity into the NSF-sponsored research.