Research On Seismic Vulnerability And Collapse Resistance Of RC Frame

In many earthquakes in recent years,RC frame structures have suffered various degrees of damage or even collapse,causing serious losses to the safety of people’s lives and property.Therefore,it is of great theoretical significance and engineering value to study the seismic collapse resistance of RC frame structures.In this paper,the incremental dynamic analysis（IDA）method is used to study the collapse resistance of RC frame structures under earthquake action.Analyze the influence of axial compression ratio,concrete strength and number of layers on the seismic vulnerability of the structure,calculate the probability of the structure reaching different damage states under different ground motion strengths,and find out the influence of the above three parameters on the collapse resistance of the structure.main tasks as follows:（1）The six-layer RC frame was established as an analysis model,and modal analysis was performed on the model using ETABS and Open SEES respectively.The period errors of the first three modes were within 4%,indicating the rationality and accuracy of the basic frame structure model.Introduced a widely used seismic response analysis method based on incremental dynamic analysis.The structural damping ratio is 5%,and the spectral acceleration S_a（T₁,5%）corresponding to the first period T1 is used as the index of ground motion intensity for structural analysis（IM）,the maximum interlayer displacement angle(θ_max)is used as the index of structural response（DM）.And the evaluation method and evaluation process of structural collapse resistance based on incremental dynamic analysis are given.（2）Based on the Open SEES software,the RC frame column and the overall RC frame structure pseudo-static test and their corresponding fiber model simulation were compared and analyzed to verify the correctness of the fiber model.The IDA analysis of the structure was conducted through Open SEES,and then the probability demand model was determined and the structural vulnerability curve was established.The collapse resistance reserve coefficient（CMR）was used to quantitatively evaluate the collapse resistance of the structure under different ground motion levels.（3）The influence law of axial compression ratio,concrete strength and number of layers on structural vulnerability was studied.Through the analysis of the vulnerability curve,it is found that under the same earthquake motion strength,as the column axial compression ratio increases,the CMR value of the structure decreases from 4.49 to 1.89,and the collapse resistance of the structure gradually decreases;under the same earthquake motion strength,Increasing the concrete strength level,the CMR value of the structure increases from 2.14 to4.30,the structure’s resistance to collapse is gradually increasing;under the same ground motion strength,as the number of layers increases,the structure’s CMR value does not show regularity.The main reason is that as the number of layers increases,the column section also increases accordingly,improving the overall collapse resistance of the structure.Therefore,the influence of the number of layers and corresponding structural measures on the collapse resistance of the structure should be comprehensively considered.