Selection Method Of The Most Unfavorable Ground Motion For Super High-rise Building Structures

Because of the particularity and importance of super high-rise structure,in order to analyze the seismic potential of super high-rise structure,the most unfavorable ground motion for super high rise structure should be selected.The most accurate determination of the most unfavorable ground motion is to find the ground motion which produce the maximum response of the structure on a given site.However,it is not realistic to carry out a large number of time history analysis for super high-rise structures.The most effective method for the determination of the most unfavorable ground motion in previous studies is mainly aimed at the structure whose period is below 5.5s.This problem remains to be solved for the selection of the most unfavorable ground motion of super high rise buildings.Based on the theory of resonance vibration,to consider the contribution of the frequencies of ground motion not equal to structure period for the incremental dynamic analysis of super high rise structures,a new parameter is proposed by the dynamic amplification coefficient multiplied by Fourier amplitude.Through theoretical derivation,the rationality of this hypothesis is proved.At the same time,corresponding modal mass participation proportions is used as weights to quantify the effects of high mode.Through correlation analysis,the most reasonable number of modes is two and finally modified Fourier amplitude is determined.The Pacific Earthquake Engineering Research(PEER)NGA-West database is selected as an alternative seismic database.Comprehensive evaluation for earthquake damage potential method,skyline query algorithm,the average spectral acceleration method,and modified Fourier amplitude methods were selected for two different structure group of the worst seismic response analysis.By comparing story drift ratio of the structures,it is found that story drift ratio obtained by the modified Fourier amplitude method is the largest.Therefore,the modified Fourier amplitude of the ground motion selection method is the most unfavorable to the super high-rise structure.On the different levels of PGA,correlation analysis is carried out between max story drift ratio of two high-rise structures and 13 kinds of ground motion intensities,3 intensities which are suitable for high-rise structures and the modified Fourier amplitude.The result shows that the correlation coefficient between the modified Fourier amplitude method and max story drift ratio is larger and more stable than others.In order to test the robustness of the modified Fourier amplitude,the P values of the modified Fourier amplitude and three intensities which are suitable for high rise structures are calculated at different levels of PGA levels.The P values obtained by modified Fourier amplitude method are far less than the other three indicators at different PGA levels,for different structures.The trend observed by the modified Fourier amplitude method is very significant in statistics.