Spatial Coherence Of Ground Motions And Practical Coherence Model

In the seismic analysis of the structure,the ground motion data needs to be input into the model.Determination of the ground motion input method is the first step of structural seismic analysis.The ground motion coherence function model is the basis of ground motion multi-point input.With the gradual improvement of the construction of dense arrays in various countries around the world,a large number of real and reliable ground motion records have been generated,which provides a data foundation for the study of ground motion spatial coherence and the establishment of coherence function.This paper discusses the necessity and feasibility of coherence function research,compares and analyzes the coherence function that has been proposed by scholars at home and abroad,and explores the characteristics and influencing factors of spatial coherence of ground motion,and puts forward a practical coherence function model.The article mainly contains the following parts:1.Based on the dense array records of the three ground motion events from the SMART-1 array,plot the coherence coefficient as a function of frequency.Under the same conditions of station spacing,analysing the coherence coefficient between the different ground motion components(between different components of the same measuring point and different components of different measuring points)and the same component of different measuring points.Provide a theoretical basis for the establishment of subsequent coherence function models.2.Based on the small station spacing,the coherence coefficient shows a decreasing trend with increasing frequency.According to the dense array data of 9 earthquake events obtained by PEER,use Chen Qingjun model for fitting.Under the same conditions of station spacing,the influence of site conditions and magnitude factors on the coherence of ground motion is discussed.3.In order to consider the influence of site conditions and magnitude factors on the coherence of ground motion,an improved coherence function model based on Chen Qingjun model is proposed,and the influence factor of considering the magnitude is added to the model.A fitting model of several station pairs was performed using the improved model,and the improved model was compared with the Chen Qingjun model.Finally,according to the site conditions and the ground motion component direction,specific value suggestions are given to facilitate practical engineering applications.