Study On Seismic Collapse Probability Spectrum Of Engineering Structures

Under the strong earthquake,the collapse of the structure is the main cause of personal injury and economic losses.In the seismic design of structures,how to improve the seismic performance of building structures and consider what damage index can truly reflect the response and damage characteristics of structures under earthquakes have always been the research focus of structural seismic researchers.At present,Park & Ang damage index model is simple in form,considering the effects of the maximum deformation and cumulative energy dissipation of the structure under earthquake action,and has been verified by actual earthquakes,so it is widely used by researchers.Based on this classic model,many scholars have proposed improved damage calculation models for different materials and different structures.Based on the Park & Ang damage model,considering the influence of moment magnitude,site,fault distance,strength reduction factor,initial period of structure and ductility factor of ultimate displacement,this paper proposes and establishes earthquake collapse probability spectra of three types of sites in China,in order to explore the regular variation characteristics of earthquake collapse spectra.The main research contents are as follows:Firstly,this paper introduces the concept,classification and the corresponding relationship with earthquake damage level of damage index.Through this correspondence,collapse probability and collapse probability spectrum are defined in this paper.Secondly,according to the energy term in the damage index calculation,the energy conversion equation is established.Newmark-? linear acceleration method is used to derive the incremental form of Newmark-? method.The restoring force model for nonlinear time history analysis in energy calculation is introduced in detail.The calculation program of collapse probability spectrum was compiled though MATLAB.Thirdly,from the NGA database in the United States,seismic records suitable for the site categories classified in China's seismic code are selected through a certain corresponding conversion relationship.The collapse probability spectra of the three types of sites in China,I,II and III,are calculated and obtained by using the program compiled by MATLAB.The influences of moment magnitude,fault distance,strength reduction factor,initial period of structure and ductility factor of ultimate displacement on collapse probability are analyzed.It is found that the structural period,moment magnitude,strength reduction factor and ultimate displacement ductility factor have significant effects on the collapse probability spectrum,while the influence of fault distance on the collapse probability spectrum is limited.Based on this result,when considering earthquake resistance,the structure with medium-long period,small strength reduction coefficient and large displacement ductility coefficient is preferred in theory..Finally,the functional relationship and fitting parameters of the collapse probability spectra of the three types of sites are obtained through regression analysis and fitting.