Seismic Performance Analysis And Evaluation Of RC Frame Strengthened With Externally Bonded Steel Based On Pushover

In recent years, with the world wide rapid development building strengthening and retrofilting trade, RC frame strengthened with encased steel as a kind of wide spread application and economical and effective method has become an important research topic. In the past, there was some research on strengthening with encased steel at component level concerning bearing capacity, seismic performance test and theoretic research. However, the seismic performance test research of frame structures at the level of integeral construction awas rarely reported. There were few literatures theoretic research on the numerical simulation of structure overall elastoplastic earthquake resistance ability of a structure.This article discusses work mechanism of the componets strengthened with encased steel. On the basis of stirrup confined concrete model and, the confining effect of concretes strengthened with encased steel has been analyzed, which provided the basis for the following earthquake resistance performance analysis of constitutive relations. In addition, the article summarized the structural earthquake resistance analysis method, systematically introduced the theoretical foundation of elastioplastic Pushover analysis method, common lateral load patterns and the structural earthquake resistance appraisal goal. In combination with a project case, the dynamic performance of the finite element software SAP2000 was adopted to analyse.Through comparison of the free vibration characteristics such as cycle and frequency of the structure before and after strengthening find that the vibration periods smaller. But from the overall, the influence of bottom columns strengthened with encased steel on the whole structure vibration cycle is not obvious. Under eight degree earthquake resistance fortification intensity, "the uniform distribution load" pattern and "the triangle distribution load" pattern were exerted and Capacity spectrum method was adopted to carry out the Pushover static nonlinear analysis. With the analysis of target displacement, interstory drift, plastic hinge and so on of a frame structure strengthened with externally bond angles, the seismic resistance of the structure was evaluated. The result indicated that, in the initial period of loading, there is little increase in the structural rigidity at the initial stage of loading, structural-load-carrying capacity is improved to some extent. With the increase of lateral load, the structure overall rigidity reduces gradually. At same displacement, the rigidity of structure strengthened with encased steel is obviously increased. Under the attack of rare earthquake, the structure enters the elastoplasticity stage when it reaches its capability point. With the bottom floor columns strengthened with encased steel, the interbedded displacement of bottom floor is greatly reduced. As the first and second floor columns are strengthened with encased steel, interbedded displacements are also decreased, and at the same time, the biggest inter-story drift ratio position move to upper story. So this kind of encased steel rigid strengthening is applicable to the cases where the floor displacement is to be reduced.