Seismic Vulnerability Analysis Of RC Fram-Bent Structures Under Near-Fault Earthquake

Because the distribution of seismic faults in China is complex,the number is large and some of them have not been found,so many cities are located near-faults or potential-faults.The damage degree of the building structure in the near-fault area is more serious than that in the general far-fault earthquake area.At present,the frame bent structure is seldom studied under near fault earthquake action.Therefore,in this paper,the nonlinear model of reinforced concrete frame-bent structure is established,and the incremental dynamic analysis(IDA)method is used to study the probability of exceeding various limit states of frame-bent structure under near-fault and general far-fault ground motions,and quantitatively analysis seismic vulnerability of frame-bent structure.The main research contents and conclusions are as follows:(1)This paper summarizes the basic characteristics of near-fault earthquakes and the differences between near-fault earthquakes and far-fault earthquakes,understands the national standards for the fortification of near-fault earthquakes,grasps and uses the Multi Pulse Analysis(MPA)method,according to the principle of the strongest energy,selects 8 pulse-like near-fault ground motions and 8 non-pulse near-fault ground motions with fault distance less than 20 km from the database of the United States earthquake research center through continuous wavelet transform For the records of ground motion,8 far-fault ground motins 80 km away are selected,with a total of 24 records.(2)The finite element software is used to establish a three-layer frame-bent structure analysis and calculation model,and 24 ground motion records are input into the frame-bent structure to conduct nonlinear dynamic response analysis.The results show that the maximum basement shear of the structure under pulse-like near-fault ground motion is 5.1 times that of far-fault ground motion and 1.47 times that of non-pulse near-fault ground motion.The maximum interlayer displacement under pulse-like near-fault ground motion is 3.8 times that of non-pulse ground motion and 19.7 times that of far-fault ground motion.The plastic hysteretic energy of the structure increases rapidly with the increase of the period of the structure under near-fault earthquake,on the contrary,the plastic hysteretic energy of the structure under far-fault earthquake is smaller.(3)IDA analysis of the structure is carried out and IDA curve clusters are obtained.Based on the results of IDA analysis,the full probability method and the semi probability method are used to calculate the probability of exceeding the five limit states of frame-bent structures.The results of vulnerability analysis show that for far-fault earthquake,when it is 8 degree frequent earthquake and basic earthquake,the five limit states of the structure was not exceeded,which well met the seismic requirements;in case of 8-degree rare earthquake,it only exceeds the limit state of normal use and the probability of exceeding is small,which meets the seismic requirements.However,the probability of the structure exceeding the service state after repair is small in case of near-fault earthquake with frequent earthquake of 8 degree.The probability of reaching the life safety state is 2.42%,and the probability of exceeding the state to prevent collapse is 10.38%in the rare earthquake,compared with the far-fault ground motions,the exceeding probability is higher.Therefore,the frame-bent structure is more vulnerable than the far-fault earthquake under the action of near-fault earthquake.The research results can provide reference for the frame-bent structure design and seismic risk assessment in the near-fault area.