Characteristic Parameter Analysis Of Elastic And Elastic-Plastic Design Spectra Based On Southwest China Ground Motion Data

Design response spectrum is an important basis for seismic design.The characteristic parameters controlling the value of design spectrum are firstly affected by statistical ground motion data,while the ground motions have significant regional differences.As a result,the characteristics of regional ground motions should be considered when determining the characteristic parameters of design spectrum.The design spectrum is based on the elastic response spectrum,but the seismic fortification in China allows the structure to enter the elastic-plastic stage.Therefore,based on performance-based seismic design,the elastic-plastic analysis of the system is carried out,and the elastoplastic design spectrum is constructed.The main research contents are as follows:（1）Based on southwest China ground motion data with high quantity,the horizontal and vertical design spectrum parameters in southwest China are calibrated by using the high-stability GLDE algorithm and the four-stage design spectrum model,showing the law of the change of design spectrum parameters in ground motion.By comparing the calibration results with the characteristic parameters of Chinese standard spectra,we give the calculation results of characteristic parameters of design spectrum in southwest China based on Chinese seismic grouping-the maximum magnification factor(β_max),the first inflection point（T₀）.the characteristic period（T_g）,the third inflection point（Td）and the downward decay index（y）.（2）Based on the calibration results,the proposed parameters of the horizontal design spectrum with regional characteristics are compared with those of the standard design spectrum,and the effects of the proposed parameters on each segment of the design spectrum are analyzed.The results show that the values,starting points and ending points of the platform segment of the designed spectrum are greater than the standard spectrum,and the falling rate of the descending segment is also greater than the standard spectrum.Different from the vertical design spectrum obtained by reducing the horizontal design spectrum on the basis of the standard spectrum,the vertical response spectrum is calculated directly in this paper,and the parameters of the vertical design spectrum are obtained.The results show that the reduction coefficient of 65%is small.In addition,the results of this paper can also provide a reference for the revision of the long period section of the standard design spectrum and the establishment of the southwest design spectrum.（3）Based on three different elastic-plastic models,the equal ductility strength reduction factor of the structure is calculated,and the whole comparison is made based on different models,ground motion direction and ductility coefficient.Based on different parameters such as source depth,epicentral distance,peak acceleration,peak velocity,peak displacement and site classification,the law of the variation of the horizontal and vertical intensity reduction coefficients with the ground motion parameters in southwest China is revealed.According to the site conditions and design seismic groups of China,the R-μ-T relation is given,and the elastic-plastic design spectrum is constructed,which reflects the seismic design concept of China.