Study On The Design Response Spectrum Of Long-period Ground Motion And The Method Of Ground Motion Selection

Because of the strong randomness of the ground motion,the seismic response of the structure varies greatly with the input ground motion.As a special kind of ground motion,long-period ground motion will make the long-period structure produce violent structural response,and even cause serious damage.However,there is not much research on long-period ground motion in China,and the code response spectrum does not take into account the influence of long-period ground motion reasonably,which can not guide engineering practice well,so it is necessary to modify the code response spectrum properly.In addition,with the acquisition of a large number of strong earthquake motion records,it is necessary to put forward a ground motion selection method which can meet the requirements of our code and is suitable for elastic and elastic-plastic analysis.The main contents of this paper are as follows:(1)The method of defining ordinary ground motion and long period ground motion is put forward: Hilbert energy spectrum is introduced to reflect the energy distribution of ground motion more accurately.From the point of view of energy,this paper defines that for a ground motion,if the ratio of the energy spectrum area to the total energy spectrum area in the 0-0.4Hz range is greater than 0.2,the ground motion is a long period ground motion.In addition,this paper also compares the difference between ordinary ground motion and long period ground motion from two aspects of response spectrum and seismic response ofstructure.The numerical example shows that the response of structure under long-period ground motion is larger than that of ordinary ground motion.(2)Recalibrate the design response spectrum: Based on 25862 strong motion records collected from Ki K-net and K-NET strong motion observation networks in Japan,the response spectra of ordinary ground motion,long period ground motion and rare ground motion are calibrated and calculated by evolutionary algorithm,and the corresponding parameters are suggested.(3)Based on the requirements of Chinese code for dynamic time-history analysis,considering the influence of high-order vibration modes and period extension of structure,combined with the basic principle of structural dynamics,two kinds of ground motion selectionmethods are proposed,which are suitable for elastic time-history analysis and elastic-plastid time-history analysis respectively.Numerical examples show that the ground motions selected by the two methods can meet the requirements of the code and effectively reduce the discreteness of the structural response.