Analysis On Seismic Fragility Of Steel Reinforced Concrete Frame Structures

Performance-based seismic design is an important part of today's seismic engineering research,which is mainly evaluated by the seismic vulnerability of the structure.The steel reinforced concrete(SRC)composite structures have been widely used in large-span structures and high-rise buildings because of their good seismic performance.In this paper,the finite element analysis and seismic vulnerability of SRC frame structure are studied.The main work and the key scientific achievements are as follows:(1)Numerical simulation and parameter analysis on seismic performance of the SRC frame structure.On the OpenSees platform,applying the Mander and modified Kent-Park concrete constitutive model and considering the restraint effect of section steel and stirrup on core concrete,the beam-column fiber unit model whose section is divided into strong and weak constraint region is suggested.The nonlinear finite element analysis on the seismic behavior of the model frame under cyclic loads is carried out,and the calculated results are much coincided with the tested results,which proves that the numerical simulation on the seismic performance of SRC frame structures based on OpenSees is accurate.And the influence of axial compression ratio,concrete strength and section steel strength on the seismic performance of SRC frame structures is analyzed by finite element simulation.The suggested values of the performance parameters are presented to provide reference for engineering design.(2)Analysis on seismic fragility of SRC frame structures.The Incremental Dynamic Analysis(IDA)is carried out for a typical nine-story SRC frame structure,and the seismic fragility analysis is carried out with the peak interstory ratios as the Engineering Demand Parameter(EDP).The predicted results conform to the structural design principles,and meet requirement for seismic design.At the same time,the vulnerability assessment results of SRC frame structures achieved by respectively using Sa and PGA as the ground motion intensity parameters are compared and discussed.The results show that the dispersion and safety reliability of the evaluation results obtained by using Sa as the intensity parameter are better than those obtained by PGA.(3)Seismic fragility analysis of SRC frame structures based on different engineering demand parameters.At present,the peak interstory ratios are mainly used as the engineering demand parameter(EDP),which does not reflect the cumulative damage caused by energy dissipation.Hence,the applicability of the material damage model proposed by YeongAe Heo for the SRC frame structure is discussed through numerical analysis,then the calculations based on material and component damage indices are realized.And the peak interstory ratio,component and material damage indices are taken as EDPs to analyze the seismic fragility of SRC frame structure,and the evaluation results are analyzed and compared.The results show that the assessment results based on drift are conservative,and results based on material damage index are unsafe.However,the achieved results for seismic vulnerability assessment of SRC frame structures based on component damage index showed to be more cost-effective,practical,and robust overall.