Seismic Fragility Analysis Of RC Frame Structure With Flexible Connected Opening Infilled Walls

Chinese architects usually regard infilled walls as non structural components when they design structures,the infilled wall in RC frame is more to separate the structure space.However,recent research found that the infilled wall will significantly change the seismic performance of RC frame,and the existence of opening makes this situation more complex.Therefore,it is suggested that the infilled wall and the frame should be separated and filled with flexible materials.The seismic fragility analysis of three different 6-storey RC frame models will be carried out,and conclusions are as follows:(1)The displacement-based beam-column element is selected as beams and columns.The infilled wall is replaced by equivalent diagonal struts and simulated by Truss element.The Two Node Link element is used to simulate flexible connection.The hysteresis curves obtained by Open Sees are in good agreement with those of experiment,and the rationality of the modeling method is verified.(2)At the beginning,IDA curves of single model increase linearly.When the value of IM increases to a certain value,the slope of a curve begins to decrease until it tends to be straight.But there are also some IDA curves with hardening or softening characteristics,this reflects the influence of the randomness of ground motion on the dynamic characteristics of a single structure.However,under the same 44 records of ground motion,due to the different structural characteristics,the IDA curves of the three models show obvious differences in the initial slope.(3)The results of seismic fragility analysis show that under the same IM,the probability of bare frame reaching or exceeding every limit state is the highest,and the probability of RC frame with rigid connection opening infilled wall reaching or exceeding every limit state is the lowest,while the probability of RC frame with flexible connection opening infilled wall is between bare frame and RC frame with rigid connection opening infilled wall.Based on the collapse margin ratio,the collapse margin of models has been analyzed.It is found that the CMR value of the bare frame is the lowest,and the CMR value of RC frame with flexible connection opening infilled wall is the highest.The existence of infilled wall improves the lateral stiffness and horizontal bearing capacity of the structure,and the actual seismic performance of RC frame with rigid connection opening infilled wall is also improved.However,when the earthquake occurs,the RC frame with rigid connection opening infilled wall may bear more earthquake action.Using high elastic rubber as flexible connection material can maintain enough bearing capacity of RC frame with opening infilled wall.At the same time,it can reduce the earthquake action that the structure may bear in the earthquake.Therefore,compared with RC frame with rigid connection opening infilled wall,RC frame with flexible connection opening infilled wall has higher safety margin and stronger ability to avoid collapsing.In the practical engineering application,if the RC frame needs to be arranged with an opening infilled wall,it is suggested to adopt flexible connection between wall and frame,and the infilled material can be high elastic rubber.(4)The collapse probability of three models designed according to the seismic code of China is less than 10% under strong earthquake,which shows that three models can meet the requirements of strong earthquake performance.