Modeling and identification of multistory buildings using seismic recordings

Abstract

This study proposes a continuous-discrete model for one-dimensional wave propagation in a multi-story building with seismic excitation and shows its applications in forward predicting analysis and inverse system identification. In particular, the building is modeled as a series of continuous shear-beams for columns/walls in inter-stories and discrete lumped-masses for floors. Wave response at one location of the building is then derived from an impulsive motion at another location in the time and frequency domains, termed here as wave-based or generalized impulse and frequency response functions (GIRF and GFRF). The GIRF and GFRF are fundamental in relating seismic wave responses at the two locations of a building structure subjected to seismic excitation that is not fully known due to the complicated soil-structure interaction. Additionally, they play a key role in characterizing seismic structural responses, as well as in identifying dynamic parameters and subsequently diagnosing local damage of the structure. For illustration, this study examines the ten-story Millikan Library in Pasadena, California with recordings of the Yorba Linda earthquake of September 3, 2002. With the use of the proposed continuous-discrete model as well as its degenerated ones, seismic wave responses are interpreted from the perspective of wave propagation, and more importantly, validated with the recordings and pertinent discrete-model-based results. Finally, a wave-based approach for system identification with a limited number of seismic recordings is presented, which can be used to evaluate structural integrity and detect damage in post-earthquake structural condition assessment.