Research On Seismic Performance Of CFRP Reinforced Non-ductile RC Frame Structures

At present,a great number of reinforced concrete(RC)frame structures have been built by using old seismic design codes in China.The seismic design of structures did not consider the horizontal loading or cannot satisfy with the current seismic code requirements due to the revision of the code for seismic design of buildings.This kind of structures is named as non-ductile RC frame structures;they have the risk of damage,and even collapse,when suffering from strong earthquake.In this way,the non-ductile structures need to be reinforced.Carbon Reinforced polymer fiber(CFRP)is widely used in the field of structural reinforcement,and it shows that wrapping CFRP is an effective method for structural reinforcement.However,the performance index,failure mode and reasonable reinforcement scheme of the CFRP reinforced non-ductile RC frame structures are in lack of study.Thus,this thesis aims to study the seismic behavior of non-ductile RC frame structure reinforced by CFRP,The main research contents and corresponding results are summarized as follows:(1)A plane RC frame structure,1/2 scaled,with two spans and two stories,which was designed without considering seismic fortification,were carried out by cyclic load.The failure mechanism of non-ductile reinforced concrete frame structure under cyclic load is revealed,and bearing capacity,energy dissipation capacity and displacement ductility coefficient of the frame structure were studied.(2)Based on Abaqus software package,the multi-scale model of non-ductile reinforced concrete frame structure was established,and the multi-scale model was verified by using the experimental data.In terms of the established multi-scale mode,damage degree of the key components and beam-column joints were studied.Based on the improved double parameter seismic damage model,the damage values at different times of each layer in the non-ductile frame structure were calculated,and the damage evolution process of the structure under earthquake was analyzed.(3)For the non-ductile reinforced concrete frame structure,this thesis proposed a strengthening scheme by using CFRP.The reinforced RC frame was tested under the same loading as the non-ductile reinforced concrete frame structure.One frame was reinforced by CFRP,and the other one was without reinforcement.The test results of the reinforced RC frame structure,such as the failure mode,bearing capacity,energy dissipation capacity and displacement ductility coefficient,were compared with these of non-ductile reinforced concrete frame structure.The results show that the strengthening scheme is reliable and applicable to future use in practical engineering.(4)This thesis adopted the response modification factor to evaluate the anti-collapse capacity of RC frame structures.Based on OpenSees platform,the finite element models of non-ductile reinforced concrete frame structure before and after by reinforced using CFRP were established,and verified by the experimental data.Because the experimental condition is limited,the structure with two spans is inconsistent with the actual project.Therefore,based on the verified numerical models,the numerical models of five stories,eight stories and ten stories of multi-span RC frame structures were established.Then,the response modification factors of RC frame structures with various stories under different earthquake magnitude(six,seven,eight and nine degree)were calculated by using elastic-plastic static analysis method to evaluate the overall anti-collapse capacity of RC frame structures.(5)An assessment method for the seismic performance of the non-ductile RC frame structure strengthened by CFRP was proposed based on probability,in which annual exceeding probability was used to assess the seismic performance of RC structures.Based on OpenSees platform,the seismic performance of reinforced and unreinforced frames was assessed.The results show that seismic performance of reinforced frame is in conformity with the requirements and has security reserve by using CFRP.In addition,compared with load and resistance factor design method,the demand and capacity factor method is closer to the actual condition.