Study On The Influence Of Ground Motion Duration On The Seismic Response Of Reinforced Concrete Frame Structures

In recent years,earthquakes occur frequently at home and abroad,resulting in huge economic losses and casualties.The extent of earthquake damage is determined by the characteristics of ground motions and the seismic performance of building structures.The amplitude,spectrum and duration are the three elements of ground motion,which determine the characteristics of ground motions.The influence of spectrum and amplitude can be quantified by response spectrum,but the seismic codes of various countries have not explicitly considered the effect of ground motion duration on the seismic response of structures.More and more scientific researchers are paying attention to the effect of ground motion duration on the seismic response of structures.With the increase of ground motion duration,the reinforced concrete（RC）frame structures are subjected to more cyclic loads,and the degree of fatigue damage increases.Therefore,it is necessary to study the impact of ground motion duration on the seismic performance of RC frame structures.In this regard,this paper uses a dynamic analysis method,inputs ground motions of different durations to the 3,6,and 9 story frame structures,and research the impact of ground motion duration on different types of seismic response parameters according to analysis results.The main research contents are as follows:（1）Four different duration indicators are introduced,significant duration D_s5-75or D_s5-95were chosen as ground motion duration analysis index.Based on the synthetic ground motion software,120 artificial ground motions are synthesized by taking the building seismic design spectrum as the target spectrum value.Three frame structures,which modeled by OpenSees finite element software,were designed under the fortification level of 7 degrees.The structural damage model parameters for calculating the hysteretic energy dissipation and damage index of the frame structure were selected.（2）The impact of ground motion duration on the parameters that didn’t consider the cumulative effect were analyzed,including maximum acceleration,maximum intensity drift ratio and vertex displacement of the structure.It was found that the slope of the fitting curve of maximum acceleration,maximum intensity drift ratio or vertex displacement and significant duration,was very small through linear fitting,That is,with the increasing of duration,the distribution states of maximum acceleration,maximum intensity drift ratio and vertex displacement remained basically unchanged.And the correlation coefficient of the fitted curve was only 0.01～0.23.It could be considered that the correlation between maximum acceleration,maximum intensity drift ratio or vertex displacement and the important duration is not strong.（3）The impact of ground motion duration on the parameters that consider the cumulative effect were analyzed,including hysteretic dissipation energy and damage index of the structure.It was found that hysteretic dissipation energy and damage index increased with the increasing of ground motion duration.For three-story and six-story structures,ground motion duration was highly correlated with hysteretic dissipation energy in most cases,and the correlation coefficient is between 0.70 and 0.88.Duration was moderately correlated with hysteretic dissipation energy,and the correlation coefficient is between 0.70 and 0.88.For the nine-story structure,the correlation between the duration and hysteretic dissipation energy and damage index is less than that of the three-story and six-story structure.