Research On Effective Energy Of Ground Motion Based On Generalized S-transform And Wave Selection

Careful selection of ground motions forms the basis for performing time history analysis of building structures.At present,the design spectrum in codes is the most popular method to select ground motion records,which does not take into account the nonstationary and duration effects of ground motion as important factors leading to the uncertainty of the time history analysis results.In this paper,the concept of effective energy of ground motion,which can characterize the nonstationary and duration effects of ground motion,is proposed to study the ground motion selection method that matches the design spectrum in codes and effective energy of ground motion simultaneously.The main research contents and conclusions are as follows.(1)Based on the time-frequency energy spectrum of ground motion records obtained by generalized S-transform,the time length and frequency width of effective energy of single-degree-of-freedom and multi-degree-of-freedom structures are investigated by considering the effects of structural characteristics such as structure type,dynamic characteristics,degree of nonlinear development and the frequency characteristics of ground motion.A simplified calculation model of the effective energy time-frequency range is established.(2)A large number of time history analysis are performed for single-degree-offreedom and multi-degree-of-freedom structures,and the effective energy characteristic parameter is reasonably defined through statistical analysis and correlation analysis.The effective energy characteristic parameter not only reflects the influence of ground motion on structural response,but also reflects the nonstationary and duration effects of ground motion.(3)The ground motion selection method that simultaneously matches the design spectrum in codes and the effective energy characteristic parameter is investigated.It is shown that the method considering the effective energy characteristic parameter can select representative records with different time-frequency characteristics and can better estimate the seismic response of the structure,while the method considering only the design spectrum matching may cause the structural response to deviate from the true response because the selected records have similar time-frequency characteristics.The research results can solve the problem of the uncertainty in ground motion selection,thus improving the reliability of the time history analysis results.