Study On The Seismic Fragility Of RC Frame Structures

Considering of the erthquake intensity level, bay widith and storeys,66 typical RC frame structures are designed according to code for seismic design of buildings(GB 50011-2010) based on the statistic characteristics of RC frame structures located in China. The key points and derivation process of analytical fragilty were stated detailly. The 32 seimic records were chosed according some rules of the ATC 63 report and the component with bigger horizontal PGA were used. The effectiveness of the 22 records recommended by ATC 63 was studied through comparing the four record sets formed by adding the new records into recommended 22 records, and then the 22 records recommended by ATC 63 were used for the nonlinear dynamic history time analysis(NDHTA) in the following papragraf.Method 1 showed the built process of the fragility function of Light, middle and extensive limit state for 66 typical RC frames. Basd on the nonlinear analysis platform OpenSEEs, the fiber model based on the force-based beam-column elements was proper to accurately simulate the damage process from light to serious limit states. The two intensity measures, such as PGA and Sa(T1), were used to build the seismic demad model, supposing the intensity measure and the engineering demand parameters(EDPs) were following the log-linear realationship. The seismic demad model was built based on the mutiple stripe methods and seven intensity levels were used. The maximum storey drift ratio was chosed as the EDP, the four limit state, such as lignt, middle, extensive and collapse, were used during the seismic capacity analysis. The fragility fuctions of each limit state were built based on displacement-based seismic fragility model and total uncertainty included the record-to-record uncertainty, capacity uncertainty and modeling uncertainty. 66 statistic samples were used to describe the correlationship between the fragility fuction paramerters, such as median value and standard deviation, and structure design parameters, such as earthquake intensity level, storeys and bay width. The class-level fragility fuction for each earthquake intensity level and each storey were created based on the PGA.Method 2 showed the built process of the fragility function of collapse limit state. The deterioration hysteric model developed by Ibarra were used to calibrate the key points of the skeleton curve and cyclic deterioration index by Haselton through the experimental datas of 255 columns, and the corresponding empirical expressions were formulatd. ModIMKPeakOriented created in the OpenSEEs were used to build the RC frame numerical model considering the shear defomation of RC joint zones. Incremental dynamic analysis method was used to calculate the collapse point. Dynamic instability point was defined as the collapse point based on the IDA cures. The numerical unconvergence problem was solved by adjust the convergence tolerances and try different algorithms on each analysis step to assure the collapse point would be got. The total uncertainty included record-to-record uncertainty and modeling uncertainty. Supposing the collapse point following the lognormal distribution, the collapse fragility curves of each typical RC frame strucrues were built based on the PGA and Sa(T1). The regular and correlationlships between collapse seimic fragility fuction and structural design parameters were analyzed with correlation matrix. The class-level collapse fragility fuction for each earthquake intensity level and each storey were created based on the PGA.Comparing the collapse fragilty function derived by the method 1 and method 2, it was obvious that the collapse probability of method 1 was lower than mehod 2. Based on the total probabiliy method, the fragilty function built by method 1 was modified by the collapse fragilty function built by method 2. Finally, the seismic fragility function of each RC frame structure was built.