Study On The Influence Of Ground Motion Duration On Damage Measures Of RC Frame Structure

In recent years,earthquakes with large magnitude and long duration have occurred frequently,such as the Wenchuan earthquake in China on May 12,2008,the Chile earthquake on February 27,2010 and the East Japan earthquake on March 11,2011.These earthquakes have caused serious damage to engineering structures,resulting in huge economic losses and casualties.This is not only related to the amplitude and the frequency content of ground motion,but also related to the duration of ground motion.How to accurately consider the influence of ground motion duration on structural seismic response is one of the important hot topics in the field of earthquake engineering.In this paper,the spectral matching method is used to match the long and short duration ground motion records,which are input into three finite element models of RC frame structures respectively,and the incremental dynamic analysis is carried out.The differences of the maximum inter-story drift ratio,hysteretic energy dissipation and damage index of the structure under long and short duration ground motion are compared.The quantitative influence of ground motion duration on the damage measures of RC frame structure is analyzed.The correlation between ground motion duration and structural damage index is studied.Based on the damage index,the quantitative influence of long and short duration ground motion on structural fragility is evaluated.The main research work and conclusions of this paper are as follows:(1)Using the response spectrum matching method,100 long-duration and 100 short-duration ground motion records with similar response spectrum and different durations are matched based on the target spectrum.The accuracy and rationality of the finite element modeling method in this paper are verified by comparing the results of OpenSees finite element numerical simulation with the results of shaking table test.The finite element models of 3,6 and 9-story RC frame structures are established by using this modeling method.(2)The long-duration and short-duration ground motion records are input into the three finite element models of RC frame structures,and the incremental dynamic analysis is carried out.The results show that the ground motion duration has little effect on the maximum inter-story drift ratio of the structure.The ratio of the maximum inter-story drift ratio of the structure under the long-duration and short-duration ground motions is basically about 1.The duration of ground motion has a great influence on the hysteretic energy dissipation of the structure.Under the same ground motion intensity,the hysteretic energy dissipation of the structure under the long duration group is 1.8～3.2 times that under the short duration group.The duration of ground motion has a great influence on the damage index of the structure.Under the same ground motion intensity,the damage index ratio of the structure under long and short duration groups is greater than 1,and the ratio increases with the increase of ground motion intensity,indicating that the greater the ground motion intensity,the more significant the effect of duration on the damage index of the structure.(3)By studying the correlation between damage index(DI)and significant duration(Ds70)of three RC frame structures under different ground motion intensities,it is concluded that the correlation between ground motion duration and structural damage index is strong,and the longer the duration,the greater the structural damage index,which also explains the high correlation between earthquake duration and damages imposed on the structures during strong shaking.By comparing the fragility curves of different failure states of the structure under long and short duration ground motions,it is found that compared with the short duration ground motion,the probability of moderate damage,severe damage and collapse of the structure under long duration ground motion is significantly increased,and the median value of the structural fragility curve is decreased by 16.7%～28.2%.