Research On Failure Mechanism Of RC Frame Structure Based On Multi-criteria Ratings System

Controlled damage is permitted for building structures subjecting to rare earthquakes. How to control the failure mechanism of structure is the key factor to achieve the expected goal of seismic fortification. The column moment capacity amplification factor(CMAF) is the key parameter to realize the desirable failure mechanism.Although code(2010 edition) has improved the coefficient, based on the existing research and the actual seismic damage, the results show that although the effect is improved, column hinge still generated. Because of this reason, many scholars advocate that the CMAF still needs to be further improved. The inertial strategy via enhancing structural resistance is a natural mechanism which is helpful to the formation of beam hinge mechanism, but it needs to pay more economic cost. Therefore, it is necessary to evaluate the CMAF with reasonable damage assessment criteria. and find a balance between economic and structural safety,so as to provide reference for the rational coefficient. Reasonable damage assessment criteria should be taken into consideration such factors as economy, post earthquake rehabilitation, safety and applicability.In this paper, reinforced concrete(RC) frames with different CMAF is the research object.The damage mechanism, evaluating the rationality of structure damage and simplified calculation method are major research aspects in the dissertation. Major contents and achievements are as follows:(1) The multi index evaluation system of seismic failure mode of RC frame structure is proposed. Economy and security are two aspects of structural seismic failure mode.Economic evaluation includes construction cost and post earthquake restoration degree, and safe evaluation is based on collapse probability.(2) The response of different CMAF structure.is compared under rare earthquake. It is concluded that the seismic response of the structure with larger CMAF is smaller, and the seismic performance is better. With the increase of CMAF, structure layer decreases damage and the distribution of structural damage is more and more uniform, which can effectively avoid the local damage mechanism. The failure mode of “strong column and weak beam” type is more and more obvious.(3) Based on the Park-Ang damage model, The influence rules of CMAF on economic index are compared.. It is concluded that with the increase of the CMAF, the BRCR, the BRTR and the BRDI are gradually reduced, but the range exhibits a trend of attenuation. The economic index of the structure increased gradually, and he range exhibits a trend of increasing.(4) Based on IDA the seismic ragility analysis, the Security of examples is compared. It is concluded that The contribution of increasing of CMAF is mainly embodied in the plastic stage,and more obvious contribution under the greater ground motion intensity. The increase of CMAF can significantly reduce the failure mode of the RC frame structure, and the safety is better, but the decreasing trend is gradually fading.(5) According to the building design service life and the structure seismic fortification standard,using he Reasonable evaluation standards, the CMAF reasonable values of the 8 degree 0.2g area grade two frame are given. The rationality of the seismic damage model of RC frame structure is explored, and the validity of the simplified calculation method is verified by an example.