| A large number of seismic historical data show that a strong earthquake is usually accompanied by multiple aftershocks.Due to the cumulative damage effect of multiple earthquakes,the earthquake damage of structures under the action of main aftershocks sequence is often more serious than that under the action of single main earthquake.As one of the most important forms of structure,masonry structure is widely used in our country,especially in rural areas,which will still exist for a long time.Therefore,in view of the lack of current seismic research on masonry structures considering the effect of mainshock-aftershock sequence,this paper,relying on typical masonry buildings,carries out research on the vulnerability of masonry structures under the effect of mainshock-aftershock sequence,which can provide support for Chinese earthquake prevention and disaster reduction work,and has important engineering significance and research value.The main research contents and conclusions of this paper are as follows:(1)Establishment of finite element model of typical masonry structure.Based on the preliminary investigation data,a typical masonry structure in Wenchuan earthquake(House 1)and a typical masonry structure in Jiangxi Province(House 2)are selected as the research objects.ABAQUS software is used to establish the three-dimensional finite element model of the structure,and modal analysis and elastoplastic time history analysis are carried out.By comparing and analyzing the basic period and earthquake damage characteristics of the structure,The rationality of the finite element model is verified,which lays a foundation for the study of the main aftershock vulnerability of masonry structures.(2)Analysis method of mainshock-aftershock vulnerability of structure and determination of main parameters.Incremental dynamic time-history analysis(IDA)is selected as the seismic vulnerability analysis method.The selection method of main aftershock is studied,and 20 real main aftershock sequences are determined by combination and amplitude modulation as ground motions for vulnerability analysis.The division of vulnerability function parameters and failure state and the definition of limit state in vulnerability analysis are determined.(3)Determination of masonry structure performance parameters under the action of mainshock-aftershock sequence.Based on the elastoplastic time-history analysis results of two masonry structures under the action of the mainshock-aftershock sequence,the aftershock damage sensitivity analysis of the interlayer displacement Angle of the structure and the overall damage energy dissipation were carried out,and the overall damage energy dissipation of the structure was verified by statistical information,and the overall damage energy dissipation was determined as the structural performance parameter.Through the linear fitting of the maximum interstorey displacement Angle and the overall damage energy dissipation,the specific mapping relationship and function expression between them are obtained,and then the limit state of masonry structure divided by the overall damage energy dissipation value is determined.(4)Main aftershock vulnerability analysis of typical masonry structures.Taking House 1 as the research object,IDA method was used to analyze the seismic vulnerability of the structure under 20 mainshock-aftershock sequence.The results show that aftershocks can cause additional damage to the structure,and the larger the damage is caused by the aftershocks,the larger the damage is.The damage level of the structure under the effect of the mainshock-aftershock sequence is higher than that under the effect of the main shock alone.When ?PGA is less than 0.6,the maximum increment of the structure limit state exceeding probability is less than 10%,and the aftershock effect is small.When ?PGA is greater than 0.6,the maximum increase of the structure’s limit state exceedance probability can reach 33.1%,and the aftershocks have a greater impact. |
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