Seismic Performance And Damage Evaluation Of SRC Column With Unsymmetrical Cross-shaped Steel Sections

At present,in the structure of SRC transfer floor,in order to ensure that the side transfer beam has enough anchorage length,the construction method of adding welded steel bracket or section steel flange opening is usually adopted.These methods are not only complex in construction,but also difficult to ensure the welding quality.If these are adopted,the seismic performance of the joint will be affected.In order to solve this technical bottleneck,this paper proposes a kind of SRC column with unsymmetrical cross-shaped steel sections,studies its seismic performance,and carries out damage assessment under low cycle reciprocating load.Based on the quasi-static test and the finite element analysis,the damage assessment criteria from material to component are established.The specific research contents and conclusions include:(1)In this paper,8 SRC columns with unsymmetrical cross-shaped steel sections were designed and made.Through the quasi-static test,the influence of the steel distribution form,the shear span ratio,the axial compression ratio and the volume stirrup ratio on the seismic performance of the specimen is investigated.At the same time,it provides the foundation for the establishment and modification of the finite element model.According to the crack development characteristics of concrete and the yield of steel bar and section steel,the damage mode of concrete is divided.And the seismic behavior of columns is analyzed by energy dissipation capacity,stiffness degradation and ductility.The test results show that the SRC columns with asymmetric steel have asymmetric failure characteristics and seismic performance.Under the same steel ratio,it has similar bearing capacity and energy consumption capacity,showing good ductility.It shows that the specimen still has good seismic performance.(2)Considering the non-uniform constraint of steel section on concrete,the finite element model is established.Based on the analysis of the damage evolution characteristics of concrete under compression,the unsymmetrical SRC columns are divided into three damage modes: bending,bending and shearing.And through multi parameter analysis,it is found that the shear span ratio and axial compression ratio are the main factors affecting the damage mode of the specimen.Then considering the above two main factors,the damage mode criterion of SRC columns with asymmetric steel is established.(3)The skeleton curve and damage index curve are used to represent the damage of components,and the transformation between material damage information and component damage information is realized through the phase corresponding relationship between the performance critical points of these two curves.That is,the material damage value corresponding to the critical point on the damage index curve is obtained from the physical critical point on the skeleton curve.The material damage value of each critical point of damage performance is calculated,and the average value is taken as the damage index.The one can not only quantify the damage degree of the specimen,but also reflect the nature of the material damage,which has a clear physical significance.On this basis,the damage evaluation criteria for three damage modes of SRC columns with asymmetrical cross section steel are established.