Research On The Most Unfavorable Design Ground Motions Of Building Structures

The nonlinear dynamic time history analysis is now recognized as the precise analytical method for the structural responses. The most popular seismic design codes in the world have the provision that the time history analysis should be carried out for substantial structures as a supplemental check to the results obtained from the response spectrum method. However, due to the complex mechanism of earthquake, the characteristics of the ground motions display immense uncertainties. As a result, the differences of the responses of the same structure are sometimes very distinct under different ground motion inputs.The recent earthquake investigation have shown that some structures have suffered an earthquake action which has a much larger value than the previously designed one. Hence, how to select ground motion inputs under this extreme state is a big problem. So far, when it comes to the problem of the choice of rational ground motion inputs, researchers and engineers at home and abroad mostly select the inputs which were recorded at the early stages, such as the El Centro ground motion (1940). Although great efforts have been made on this subject, no consistent conclusions have been achieved. On the basis of ground motions that have been collected, this study presents the vast statistical analysis to find out the parameters that can reflect the damage potential of the ground motions, and then the unfavorable ground motions are given.The main contents of this study consist of the following:(1) A summary of the parameters that can reflect the damage potential of ground motions is made. Then the seismic parameters that will be used in this study have been selected; Based on the structural models which were established according to the Chinese codes, the damage states of each model are analyzed by the time history analyses and then the overall structure damage indices are obtained.(2) For the near-fault pulse-like ground motions and far-field ground motions, the correlation analyses between the seismic parameters and the overall structure damage indices are carried out.And the parameters that can characterize the damage potential of each kind of ground motion are found out.(3) The guideline that can be used to select the ground motions are established, through this formula the most unfavourable design ground motions are determined from the collected database of ground motion records.