Experimental Investigation Of CFRP-retrofitted Earthquake-damaged Masonry Infilled RC Frames

Masonry infilled reinforced concrete(RC)frame structure is one of the most widely used structural systems in the world.In recent years,there have been many serious earthquake disasters around the world.The existence of infilled wall will affect the force of the frame,and the force of the frame structures with the infilled wall with opening become more comple.As a result,many masonry infilled RC frame structures suffer varying degrees of damage.Some buildings have collapsed and cannot be used any more,however,a considerable number of buildings can still be used after repair and retrofit.Carbon Fiber Reinforced Polymer(CFRP)is widely used in the reinforcement industry because of its excellent performance,such as corrosion resistance,light weight and high strength.Therefore,it is very necessary to study the CFRP-retrofitted earthquake-damaged RC frame structures.Three masonry infilled RC frame specimens damaged in the initial quasistatic test and one RC frame specimen without damage were studied in this paper,the details of the research are following.(1)The scheme of repairing and retrofitting the specimens was designed in this paper according to the code,including the repair of concrete,the area of pasting CFRP,the number of CFRP and the way of pasting CFRP.Then four specimens bad been repaired and retrofitted according to the determined scheme and the relevant requirements of the code.(2)The four retrofitted specimens were tested through reversed cyclic quasistatic tests in this paper.During the loading process,it was found that the failure mode of the RC frame was changed compared with that before the reinforcement,especially in the definite reduction of damaged condition and improvement of ductility.And without the reinforcement of CFRP,the failure mode of the wall with opening was the same as before.(3)Through the experimental data,the hysteresis curve,skeleton curve,stiffness degradation curve,energy curve,strength degradation coefficient and ductility coefficient of the specimens were obtained.By contrast,the results show that:the bearing capacity,energy dissipation capacity and ductility of the specimens strengthened by CFRP were all improved,and the stiffness degradation rate was slower,but the initial stiffness of the specimens is slightly lower than that of the specimens without damage.(4)Based on OpenSees,the masonry infilled RC frame specimens were modeled.The beam and column were simulated by nonlinear beam-column element which was defined with dispBeamColumn in OpenSees.The infill wall was simulated by equivalent strut which was defined by Truss in OpenSees with the four branches skeleton curve model proposed by Panagiotakos and Fardis.For the infill wall with opening,considering the influence of the size and position of the opening,the calculation formulas proposed by Mansouri A and Akhoundi F are used to reduce the stiffness and strength of the infill wall.The simulation results were in good agreement with the experimental results,which verified the accuracy and applicability of the model established in this paper.