Input Identification from Structural Vibrational Response

摘要

The equivalent linearization method is applied to input identification from known structural response and system parameters, working in frequency domain. In addition to the commonly used one-model procedure, a two-model input identification procedure is proposed. Numerical examples of structural systems having elements of bilinear force-deformation relations are presented for different cases of stiffness, input motion and level of nonlinearity. Structural response obtained from true hysteretic loop analyses are used as the known responses with the unknown input motions to be identified. These identified motions are then compared with the real motions to check agreement with their maximum accelerations, response spectra, Fourier amplitude spectra, and acceleration time-histories. Shaking table tests of two three-story braced steel frames are used as examples to check the accuracy of the suggested input identification procedure. The bracing systems used, show strong nonlinearities due to buckling and material yielding. Sources of error in the analysis are discussed and possible improvements of the input identification procedure are suggested.