Study On Mechanical Properties Of Concrete Filled Rectangular Steel Tubular Column To Steel Beam Joints

With the continuous development of engineering construction in recent years,concrete-filled steel tubular(CFST)structures have been widely used.The joint plays a crucial role in the security and integrity of the structure.Therefore,it has important value and significance to further study the mechanical properties of structural joints for the popularization and application of concrete filled steel tubular structures.In this paper,the mechanical properties of three kinds of concrete filled rectangular steel tube column-steel beam joints are studied by numerical simulation when the joints are subjected to monotonic loading and low cyclic loading.Furthermore,shear load-carrying capacity of joint region is analyzed.The details are as follows:(1)The ABAQUS software is used to establish the finite element models of joints,and the analysis results are compared with the results of experiments on skeleton curves and failure modes.The results show that the finite element modeling method in this paper is reliable.(2)Based on the reliable finite element modeling method,three types of finite element models for concrete filled steel tubular column-steel beam joints(Internal diaphragm joint,Diaphragm-through joint,Outer reinforced diaphragm joint)are established.The mechanical properties of these three kinds of joints are compared,and the result shows that:Diaphragm-through joints have higher load-bearing capacity and better energy dissipation capacity,while the properties of ductility,stiffness degradation,and strength degradation of Internal diaphragm joints and Outer reinforced diaphragms joints are better.Further researches are made on the influence of concrete strength,steel grade and axial compression ratio to the skeleton curves of the three kinds of joints.The results show that the influence of steel grade is the most obvious,and the effect of axial compression ratio is small.(3)The model of joint region is established by finite element software ABAQUS,the shear load-carrying capacity of the core concrete of different joints is obtained by using the numerical simulation results and principle of virtual work.Considering the contribution of each part of the joint to the shear load-carrying capacity,the shear load-carrying capacity formula of the joint region is obtained.The results based on the formula in this paper areconsistent with numerical simulation results and experimental results,which can provide references for practical engineering.