Experimental And Theoretical Study On The Seismic Performance Of RACFST Frame Infilled With RHB Filler Wall

Recycled aggregate concrete filled steel tube(RACFST)frame infilled with recycled hollow block(RHB)not only has the advantages of good mechanical properties,but also can make full use of waste concrete blocks.Therefore,this kind of structures has broad engineering application.In this paper,based on the previous study results of our research group,the low cycle loading experiment was carried out on the RACFST frame infilled with RHB filler wall from the structural level.In this way,the seismic performance of this kind of frame structures was studied,and the influence of the RHB filler wall was analyzed deeply.The research results of this paper can provide references for the further engineering application and theoretical analyses of this kind of frame structures.The test results show that the specimen experiences elastic stage,elastic-plastic stage and failure stage in the loading process.The failure process of the specimen is infilled wall failure→RAC beam failure→column base bulging.The existence of RHB infilled wall can be the first anti-seismic line of RACFST frame.The failure mode of the specimen conforms to the seismic requirements of strong column weak beam,strong node weak member and strong shear weak bending.The hysteretic curve of the specimen presents a full shuttle shape,and the equivalent viscous damping coefficient exceeds 0.20 when the specimen failed,which shows the structure has good energy dissipation ability.The positive and negative skeleton curve has good symmetry at the initial loading stage.However,the symmetry gradually becomes worse when the specimen enters to the elastic-plastic stage and failure stage.Compared to the frame without infilled wall,the bearing capacity and ductility coefficient of the frame with infilled wall increase by 8.59% and 15.30%,respectively,which shows the existence of RHB infilled wall can improve the bearing capacity and elastic-plastic deformation ability of RACFST frame.The interlayer displacement angle is between1/89～1/104 when the specimen yielded,which can satisfy the elastic deformation requirement when the frequent earthquake occurred.And the interlayer displacement angle is about 1/35 when the specimen failed,which shows the frame structure has good collapse resistance.The existence of RHB infilled wall can effectively improve the lateral stiffness of RACFST frame at the initial stage,but has little effect on its residual stiffness.With the increase of the loading displacement,the lateral stiffness of the specimen decreases gradually,and the degradation rate shows a trend of fast first and slow later.Before the infilled wall failed,the existence of RHB infilled wall can improve the energy dissipation ability of RACFST frame.However,the existence of RHB infilled wall will decrease the energy dissipation ability of RACFST frame after the infilled wall failed.In addition,this paper also verifies that the RAC beam and RACFST column accord with the plane section assumption,which can provide a basis for the further theoretical research.Finally,based on the test results,the skeleton curve model,hysteretic rule and unloading stiffness of the specimen were analyzed,respectively,and the theoretical assumptions of the bearing capacity suddenly drop and the hysteretic curve goes to fixed point were adopted.In this way,the four poly-line restoring force model which was suited for this kind of frame structures was established,and the model has good agreement with the experimental results.Subsequently,based on the Fajfar single parameter and Park-Ang double parameters damage models,the damage evolution process of the specimen was analyzed.And the damage evolution characteristics were obtained,which can provide references for the further theoretical research and engineering application of this kind of frame structures.