Study Of IDA Based On Artificial Ground Motion

The seismic capacity of building structures is an important part of structural engineering research.The traditional structural seismic design is based on the response spectrum theory,which consider the relationship between the dynamic characteristics of the structure and the ground motion characteristics,and the elastic reaction is assumed.In this theory,the construction cost is high if the structure is designed to guarantee safety under big earthquake.Therefore,the performance-based seismic design theory is proposed,the method is based on elasto-plastic time history analysis(IDA method)under a large number of ground motion.The input ground motion must be selected reasonable for the elastoplastic time history analysis of the structure.Sinec the actual ground motion is a very complex random process,the synthesis of statistically significant artificial earthquake will grealty reduce the compution of IDA.At present,the synthesis of artificial ground motion is based on the fitting target response spectrum.The rationality evaluation of the artificial ground motion is the accuracy of the produced response spectrum to the target response spectrum,and the synthesis parameters of artificial ground motion and the impact of structural elastoplastic time history analysis have not been studied.Therefore,the aim of this paper is to investigate the influence of different fitting parameters in artificial earthquake and structural hysteresis parameters on elastictoplastic time-history analysis,the main studies are as follows:(1)The engineering characteristics of ground motion and selection principle of time-history analysis input ground motion analysis are summarized and analyzed,and 21 actual ground motion are selected as a data source based on the station and seismic information,the average response spectrum is calculated as the target response spectrum.And according to this response spectrum and the basic method of synthetic artificial ground motion,artificial ground motion with different fitting parameters are synthesized by Matlab program.(2)Four different cycles of single degree of freedom system are established by finite element software OpenSees,and the structure is analyzed With different fitting parameters artificial ground motion and actual ground motion as input ground motion by IDA method.Through the discussion rise,smooth and decay time control points of the intense envelope,study the effect of strength shape on the artfical ground motion IDA analysis.The research shows:The shape of the strength envelope has a certain effect on the accuracy of the artificial ground motion and the peak acceleration.The length of time and the distribution on the time axis have a significant effect on the elastic-plastic response of the structure.(3)By studying the effects of the duration of the artificial earthquake,the damping of the target response spectrum and the phase on the structural IDA analysis.The research shows:The effect of hold time on structural elasto-plasticity is mainly manifested in cumulative damage,but its influence is related to structural period and ground motion intensity;The damping not only affects the magnitude of the artifical ground motion but also its frequency components,when selecting the target response spectrum damping coefficient,it should be consistent with the analysis structure damping;The elastic response of the phase to the artificial ground motion is directly related to the structural cycle,and it can effectively improve the fitting accuracy of artificial ground motion by reasonably improving the phase.(4)The effects of hysteresis characteristics such as ductility coefficient,strengthening coefficient,softening coefficient,hysteresis gripping and stiffness degradation on the IDA analysis of artificial ground motion are analyzed,The research shows that increasing the ductility coefficient can significantly improve the seismic performance of the structure.But also it has a great impact on the dispersion caused by the uncertainty of the ground motion and the elasto-plastic response of the artificial ground motion.The effect of different hysteresis characteristics on the elasto-plastic analysis of man-made ground motion is mainly manifested in the variation of the stiffness of the control structure at different stages.The parameters which greatly affects the stiffness of structure has great influence on the elastoplastic analysis results of artificial ground motion.