Seismic random vibration analysis of tall buildings

A highly efficient random vibration algorithm, the pseudo-excitation method (PEM), is developed for the random vibration analysis of seismic responses of tall buildings. A 40-storey tall building and a 79-storey super tall building are considered in this paper to illustrate the application of the PEM in the seismic analysis of tall buildings under random seismic actions. The finite element model of the 79-storey building has 18 171 nodes, 23 976 three-dimensional beam elements, 6057 membrane elements and 40 837 degrees of freedom. Seismic random vibration analysis of such a complex three-dimensional model can hardly be found in the literature because of low computational efficiency of the conventional random vibration methods. By using the PEM, the power spectrum densities of the structural responses can be obtained in a convenient and efficient way. This algorithm is an accurate complete quadratic combination (CQC) method because the cross-correlation terms between different modes are considered. The computation results show that random vibration analysis of the super tall building with large numbers of degrees of freedom can be conducted conveniently by the PEM on an ordinary personal computer, since the algorithm makes the structural stationary random response analysis be reduced to the analysis of structural harmonic response. In addition, the effects of several factors such as frequency integration interval and integration region, foundation conditions, number of participant modes and duration of earthquake excitation on the seismic random responses of the two tall buildings are presented and discussed in detail. (C) 2004 Elsevier Ltd. All rights reserved.