Seismic History Analysis of Asymmetric Buildings with Soil–Structure Interaction

Abstract

An efficient approximate method that uses the multi-degrees-of-freedom (MDOF) modal equations of motion for the seismic response history analysis of asymmetric elastic buildings with soil–structure interaction (SSI) is presented in this paper. The systems considered are two-way asymmetric shear buildings resting on the surface of an elastic half-space, which are excited by two-directional seismic ground motions. The SSI forces were simulated using frequency-independent soil springs and dashpots. First, the MDOF modal equations of motion for the SSI systems were derived. The modal response histories were obtained by solving the MDOF modal equations of motion using the step-by-step integration method. Subsequently, the seismic response histories of the whole SSI system were determined from the arithmetic summation of the modal response histories. The MDOF modal equations of motion retain the property of nonproportional damping of the original SSI system. The proposed method has the advantages of the conventional modal response history analysis, which requires only the first few vibration modes to obtain accurate analytical results. Finally, the efficiency of the proposed method was validated using numerical examples of a two-way asymmetric four-story building with large and small SSI effects.