Seismic Fragility Analysis Of Nonductile RC Frame Structures Retrofitted With FRP

In previous earthquake events, it have been reported that a number of existingreinforced concrete (RC) frames experienced severe damage, or even collapsed,due to insufficient ductility and energy dissipation capacity. Fiber reinforcedpolymer (FRP) composites have been widely used for sismic strengthening orrehabilitation of concrete strucutures, which can improve the ductility and energydissipation capacity of the structure. Therefore, based on non-ductile RC framestructure as the research object, the seismic fragility analysis method as the researchtool, to evaluate and optimize the FRP reinforcement scheme as the researchpurpose, the seismic performance of on-ductile RC frame structure which isstrengthened with FRP is Systematic studied. The main contents are as follows:(1) Through the PKPM software, the different heights non-ductile RC framestructure was designed with the old seismic design code. Based on the nonlinearstatic Pushover and time history analysis, the ductility and energy dissipationcapacity of the sturctures were evaluated, determining the position of the weak layerto provide the basis for determining the FRP strengthening scheme.(2) Three kinds of FRP reinforcement scheme were designed. Based on theOpenSees finite element analysis platform, the finite element model of the structurebefore and after reinforcement were established. Based on the nonlinear staticPushover and time history analysis, the influence of FRP reinforcement scheme onthe seismic performance was analyzed from the perspective of certainty analysis.Strengthening reinforced concrete frame structure with FRP, FRP mainly influencethe performance of the structure in the nonlinear phase, when the structure is in theelastic stage, the effect of FRP is very small.(3) Selecting Saas the intensity of ground motion parameters, maximum driftratio θmaxas the seismic demand parameters, the probabilistic seismic demandanalysis of the structures before and after reinforcement is made by cloud method,and the uncertainty of ground motion is considered in the analysis. At the sameseismic level, FRP reinforcement of the structure has little effect on the maximumdisplacement reaction, namely FRP reinforcement does not reduce seismic demandof the structure.(4) Based on the Pushover curves, using the overall damage control principle,the seismic capacity analysis was made on the structure of FRP reinforcement,determining the drift ratio of the structures under the different limit states.According to the results of probabilistic seismic demand analysis and seismiccapacity analysis, use the analytical methods to obtain the seismic fragility curves of the structures, the quantitative evaluation of the three kinds of FRP reinforcementscheme adopted in this paper was made from the perspective of probability.(5) As the most serious problem of non-ductile RC frame structures, theseismic collapse resistance of the structures with different FRP reinforcementschemes was analyzed based on the IDA method. In order to illustrate the degree ofthe capaicity of seismic collapse resistance improved by FRP reinforcement,non-ductile RC frame structure was re-designed to compare with the three kinds ofFRP reinforcement scheme adopted in this paper, clearly understanding theimproving on collapse resistance level of FRP reinforcement schemes.