Fem Analysis On The Seismic Performance Of Concrete Frames Retrofitted With In-filled Brb-braced Steel Frames

China is a quake-prone country. Many earthquakes in past hundreds years hadbrought inestimable damages for people’s life and safety. Rural townships who haveso many people, underdeveloped economy and other disadvantages don’t builtbuilding, which have enough capacity to resist earthquake. The existed buildings weredamaged seriously in Wen-chuan and Yu-shu, and not only these buildings’anti-seismic capacities were low, but also some of them were based on the old codes.So, the existed concrete frames’ retrofitting is very important, because itconcerns social stability and life.BRB as a new type of energy dissipation brace, it canyield in both tension and compression without buckling, has good dissipation capacity,which overcomes the shortcomings of traditional common brace’s buckling andgravity is low.BRB have been applied to projects widely in the word to improve theanti-seismic capacities when the main and large earthquake happen.The capacity of load bearing and seismic resistance performance on the existingframes are not enough to meet requirement. On an experimental study aboutreinforced concrete frames retrofitted with in-filled steel frames-BRBs basis, thepaper makes non-linear finite element analysis on three models to get furtherreasonable retrofitting parameters. Two of them are retrofitted with in-filled steelframes-BRBs (BRBCF), and the other one is an ordinary frame. During the finiteelement simulation process by ABAQUS, the load is applied with the method ofdisplacement increment, and the model of steel is hardening elastic-plastic model, andthe concrete`s model is damaged plastic model. The skeleton curves which areobtained by numerical simulation are compared with the experiments. The procedureof structure inner load-bearing capacity, inner force re-distribution and the mechanicalperformance of joints are analyzed. It can supply with scientific basis for thefollowing research with in-filled steel frames-BRBs to improve inner structure,optimize structure design. The result of FEM shows that BRB by inner steel framescan enhance the resist lateral stiffness, load capacity and don’t bring burden tooriginal frames. Inner force re-distribution is obvious and BRB’s distortion is stable.On the above models basis, this paper gets other failure mode and inner forcedistribution by changing the parameters of BRB. By the contrast analysis between these results, this paper suggests some advises for the retrofitting:(1) the loadcapacity of original frames is very important when retrofitting the existed frames.(2)the (N-M,N-V)envelope diagram of pre-embedded part in beam and column byoverall process analysis can be used for the most unfavorable combination of theselected plan of BRB, to get the security evaluation in elastic-plastic stage ofstructures. It can provide model for further study by the study of this paper, becausethe laws of changing in load capacity and failure mode is all known through this paperstudy.