Seismic Evaluation Of Existing Reinforced Concrete Frame Structures

A lot of earthquake damages at home and abroad have showed with the passage of timeexisting building structures built in different years will produce the durability injury under theinfluence of various external and internal factors, which cause the seismic performance of thestructure to reduce, and the structure will be more prone to destruct during the earthquake.Seismic performance assessment methods used in the existing building structures just stay atthe qualitative assessment level, and not consider the member’s durability injury according tothe characteristics of the existing structures. Both of them will not truly reflect the seismicperformance of existing structures. Therefore, it is of great significance to take appropriatequantitative assessment methods based on the characteristics of the existing structures, andaccordingly to take appropriate and reasonable reinforcement measures for effectivelyreducing casualties and property losses caused by the earthquake．This paper, an existing reinforced concrete frame structure located in8-degree area asthe background, using ETABS finite element analysis software, and based on the resilienceskeleton curve of damaged members establish the corroded reinforced concrete framestructure model. In this model plastic hinge unit is added to simulate the nonlinear behavior ofthe component. Nonlinear Static Analysis (Push-over) as the theoretical basis, seismicperformance assessment is taken on existing structures which steel corrosion rate of0%,10%,15%and20%. During the evaluation process, equal risk probability theory is used to valuethe earthquake parameters needed for the assessment, and consider the follow-up serviceperiod of50years,30years,20years and10years. Uniform acceleration distribution andvibration mode distribution are used in the definition of push-over conditions, to consider theimpact of different lateral force load mode to the assessment results.By comparing the results of the analysis of the above various models, the followingconclusions can be drawn:1) With the increase in the rate of steel corrosion, the carryingcapacity, lateral stiffness and ductility of the structure showed a decreasing trend. Thestructure of steel corrosion rate of20%compared to the structure of the corrosion rate of0%,its base shear in yield state is reduced by about9%to19%, and it’s length of the yield plateauis shorten by about40%to50%.2) Under the frequent earthquake and rare earthquake, withshorter follow-up period of service, the base shear and top displacement in the performancepoint of existing structures showed a decreasing trend, which shows that the follow-up periodof service shortened interested in earthquake reduction.3) The structure in the vibration modeloading mode compared to the uniform acceleration loading mode, it’s yield strength andyield displacement reduce in various degrees, which indicates that the carrying capacity and lateral stiffness of the structure in the vibration mode loading mode are smaller than thestructure in the uniform acceleration loading mode.Through this study，it’s entirely feasible to evaluate the seismic performance of existingstructures using the static nonlinear analysis method (Push-over)．During analysis it needs toconsider the earthquake reduction caused by follow-up period of service shortening andperformance degradation of reinforced concrete components，and choose the right lateral loaddistribution pattern based on structural features，in order to make a real evaluation of seismicperformance of the structure．...