| The severe damage or collapse of existing buildings in earthquake is one of thereasons that cause the losses of life and poperty. So it is of great significance to studythe seismic performance of exciting RC frame structures.In common atmospheric environment, concrete carbonation is the main factor thatcauses the steel corrosion. In this paper, SAP2000, a software of finite-elementanalysis, is selected to build the modles of exciting RC frame structures and getdifferent modles’ pushover curves on three lateral forces through pushover analysis.Based on the above works, a seismic evaluation method based on displacement angle isapplied to evaluate the seismic performance of existing RC frame structures. The mainresearch are as follows:This paper expoundes the degraded material constitutive relation models, andtakes a theoratical derivation on the bearing capacity of beam and column. Thetheoretical analysis indicates that with the increase of material degradation degree, thebearing capacity of beam and column are in a falling trend.Existing structures models (the new, used5years,20years,60years) can beobtained by modifying the constitutive relation model of steel and concrete in SAP.The paper gets the above different modles’ pushover curves under three lateral forces(uniform, inverted triangle, the first vibration mode) through pushover analysis. Theanalysis results show that at the same performance status, with the increase of workinglife, the base shear and energy dissipation of existing structures are slightly reduced.In order to make a equivalent linearization on the pushover curves, Energy andparabolic methods are adopted to get the yield points. The computed results show thatthe yield points get by the energy method is small, however the parabola method isreasonable.Under all the above results, a seismic evaluation method based on displacementangle is applied to evaluate the seismic performance of existing RC frame structures.The results show that material degradation of the existing buildings has much greaterimpact in high intensity area than in low intensity area.The paper studies the development and evolution of the component section plastichinge at the different performance status and different working life, and the change rule of plastic hinge along the height. The conclusion can be obtained eventually thatthe plastic deformation capacity of structures can be weakened by the materialdegradation. |
