Study On Axial Compressive Behavior Of Concrete Confined By Tapered Circle Steel Tube

According to the mechanical characteristics of steel pipe outsourcing concrete,it can be subdivided into two main forms,namely the concrete filled steel tube and steel tubed concrete.Under vertical load,the steel pipe of concrete filled steel tube both bears vertical load directly and constraints concrete,but the steel pipe of steel tubed concrete doesn't bear vertical load directly.Both forms of composition are passive constraints model.In order to improve the bearing capacity of the reinforced concrete column ends,this paper put forward a new idea which is adding tapered steel tube with a local constraints at the end of reinforced concrete column.Under vertical load,only the tapered steel tube at one end of the specimen bears vertical load directly;on the other side it can slip relatively,and in the process of slip,steel tube can provide active constraints on the concrete.In order to study the feasibility of this new type of steel tube confined concrete,this paper studies the mechanical properties of the concrete confined by tapered circle steel tube under axial compression state.Firstly,we have designed and produced six types of specimens,namely five kinds of the concrete confined by tapered circle steel tube specimen and one kind of concrete specimen;the number of each type specimen is two,a total of twelve specimens.Main influence parameters include the angle of tapered steel tube with horizontal plane and whether to set stiffening rib.The results show that the specimens occurred local buckling in the process of axial compression;on the premise of other parameters were constant,with the decrease of the steel pipe inclination angle,the bearing capacity of the specimens,the elastic stiffness increased and the ductility of descending branch reduced;initial lateral deformation coefficient increased at the same time,and the steel tube provided active constraints earlier.Setting stiffener rib made the bearing capacity and local stability of the specimens increased correspondingly,but the stiffening rib did not significantly affect the elastic stiffness and the ductility of descending branch.Secondly,with the help of finite element analysis software of which name is ABAQUS,this paper makes numerical simulation on the concrete confined by tapered circle steel tube;through the comparison with test data,this article verifies the rationality of the finite element analysis model from the aspects of the load-displacement curve,the bearing capacity,the elastic stiffness.Afterwards,this paper carries out a supplementary simulation analysis of otherinfluencing parameters on this basis,including height of the specimen,diameter of top surface of the concrete,thickness of steel tube,number and size of stiffening rib.Finally,based on the results of test and finite element simulation analysis,this paper puts forward the calculation formula of the bearing capacity of tapered round steel tube confined concrete under axial compression on the basis of Mander et al.Model of confined concrete.By comparison of the theoretical calculation value with experimental value and finite element simulation analysis value,the formula is of high accuracy within a certain range,and it can be used in subsequent analysis and guidance of this kind of engineering design.