Structural System Identification of Buildings by a Wave Method Based on a Nonuniform Timoshenko Beam Model

Abstract

A nonuniform Timoshenko beam model of a building, with piecewise constant properties along the height, is presented, along with an algorithm for structural system identification from earthquake records. The model accounts for shear and flexural deformation, rotatory inertia, and variation of building properties with height. The model stiffness parameters are identified by matching (in the least-squares sense) propagating pulses in impulse response functions. To minimize the effects of soil–structure interaction, the fit is performed on a band excluding the fundamental mode of vibration. This algorithm is a new development in a wave method for structural health monitoring of buildings, intended for use in seismic alert systems to facilitate decision making on evacuation immediately after the earthquake, and for general condition monitoring. The model can also be used with an earthquake early warning system for quick linear response prediction to decide on safe shutdown of sensitive equipment in advance of strong shaking. Identification and response prediction are demonstrated on the north–south response of the Los Angeles 54-story Office Building, a tall, steel-frame building in downtown Los Angeles.