Study On Seismic Design Response Spectrum Of Hydraulic Structure Based On Japan KiK-net Downhole Array Data

The response spectrum refers to the maximum acceleration response,velocity response and displacement response of a single mass point system with a certain damping effect during a certain ground motion.Currently design response spectrum method is widely used around the world,and the basic principle of design response spectrum method is to forecast the maximum acceleration response of structure during an earthquake ground motion based on the acceleration response spectrum,which could be used in seismic design of structures.In theory,the design response spectrum should vary with different geological conditions,but the design response spectrum methods in some codes are simplified by experience design method without considering the influences of geology and site conditions,which need to be improved and more representative of real seismic effects.In this paper,more than 1400 groups of KiK-net earthquake data in Japan are analyzed,and the sites are classified according to site classification methods of specifications for seismic design of hydraulic structures(DL5073)and Eurocode 8 respectively.Then average response spectrum curves of different site conditions are calculated and calibrated,followed by comparing with the design response spectra in codes,and finally modification Suggestions to optimize the design response spectrum are proposed.Bedrock average spectrum and amplification spectrum are obtained by bedrock seismic motion data,comparing with ground response spectrum to verify variation of response spectrum curves.Site response software is written based on study of seismic wave with principle of signal,predicting ground motion from bedrock motion,and the influence of soil layer on seismic wave propagation is studied.The results show that site conditions have an effect on the characteristic period of the response spectrum,the height of the platform and the decrease rate of the descending segment.Through the comparison of the response spectrum of various sites,it is found that the height of the platform decreases gradually as the site is softer,which is different from the provisions of specifications for seismic design of hydraulic structures and Eurocode 8.In long period,acceleration response of structures with large natural vibration period is greater on softer site.There is no obvious difference in the response spectra of bedrock of varied site conditions.The difference of ground response spectra is completely caused by different amplification effect of soil layers of varied site conditions.The values of response spectra of different site types vary in different period segments,which is due to the filtering effect of various sites on the seismic wave frequency.The contents of surface seismic wave frequency are related to the hardness of the site.The frequency components of ground seismic wave are related to the degree of hardness of the sites.