Research On Modeling Of Hysteretic Characteristics Of RC Frames Damaged During Earthquake

Destructive earthquakes occurred occasionally in our country, which led to a large number of damaged building structures, but this does not mean that all buildings are seriously damaged or collapsed, there are a large number of earthquake damaged structures still have certain residual bearing capacity and the repair ability. Therefore, it is significance to evaluate the seismic performance of earthquake-damaged reinforced concrete structures. Earthquake damaged structures are different from the new ones, when the damaged structures suffer from earthquakes in the follow-up service period, the strength, stiffness and other mechanical properties of structure have degraded. Study content about the seismic performance evaluation of seismic damaged reinforced concrete frame structure is wide. This paper took RC frame structure as the object, and to determine the hysteretic model of seismic damaged reinforced concrete frame were deply studied in this paper. The main contents and results of this paper as following:①On the basis of existing research results, the ideas and methods to detetmine the hysteretic model of seismic damaged reinforced concrete frame were given, and the hysteresis curve datas of 97 reinforced concrete members under cyclic loading were selected from the Pacific Earthquake Engineering Research Center in the study.② According to the hysteresis curve datas of 97 reinforced concrete members under cyclic loading, the damage index values corresponding to different damage status of 97 damaged concrete members were calculated using the Park-Ang damage index calculation formula. Through regression analysis, Respectively, the fitting relations between stiffness(strength, hysteretic parameters) degradation coefficient and damage index values of damaged members were obtained, and on this basis, hysteretic model of reinforced concrete frame based on the degree of earthquake damage was given. And the prediction formula of strength degradation coefficient was properly modified. At the same time, results show that the prediction formulas according to 97 specimens are reliable by adding test datas of 18 reinforced concrete members under cyclic loading into regression analysis.③ By using the Open Sees program as a platform, the applicability of the modified Ibarra-Medina-Krawinkler hysteretic degradation model was verified. The model can well reflect the strength and stiffness degradation of reinforced concrete members under cyclic loading. It is reasonable and feasible to carry on structural dynamic elastic-plastic time history analysis using the model to define plastic hinges of components. It is not only applicable to intact structure, but also suitable to seismic damaged reinforced concrete frame structure by reduction of RC member’s strength, stiffness and hysteretic energy parameters according to the damage degree.④ By using the modified Ibarra-Medina-Krawinkler degradation model to define plastic hinges of intact and seismic damaged reinforced concrete members, and from the two aspects: the simulation of RC members under cyclic loading and dynamic elastic-plastic time history analysis of frame structures, hysteretic model of reinforced concrete frame based on the degree of earthquake damage proposed by this paper was verified reasonable. By the design of comparison calculation models considering earthquake damage or not, the influence caused by earthquake damage can not be ignored when elastic-plastic seismic response analysis carried on seismic damaged reinforced concrete frame structures.