Research On Shear Bearing Capacity And Failure Modes Of Composite RCS Joints With Tapered-flange-type Details

The use of composite reinforced concrete column and steel beam(RCS) frame structures can make full use of the performance of steel and concrete materials.But the traditional joints are difficult construction. In order to promote the RCS composite frame structure in practical engineering, our team proposed a novel RCS interior joint with continuously web plates and tapered-flange-type details for solve the construction difficulties.This paper is based on the test results, study the reason of different failure modes of RCS joints with tapered-flange-type details, and various types of joint details impact on joints failure mode and shear bearing capacity with FEM simulation and theoretical analysis, and give the corresponding design suggestions.Firstly, A typical specimen RCSJ-1 models were established by finite element program ABAQUS and ABAQUS through setting suitable parameters can simulate the mechanical properties of composite RCS joints under the reversed loading. Meanwhile preliminary analysis of the local failure causes and stress mechanism of the specimen RCSJ-1, which concrete were crushed out in the end of column and in the interior part of joint. On this basis, through the finite element modeling and analysis, the influence of the length of flange extends into the joint on failure process and failure modes of the joints are deeply discussed, the length should not be less than 0.3 column depth. By the analysis, this novel joint easily damaged in the end of column and the composite action of steel and concrete is poor.Secondly, For these two reasons, respectively, two kinds of improving methods is improved, one is through column stirrup densification above and below the beam or increasing the column section, to improve the bearing capacity of the concrete column.Other one is through extended face bearing plates, web welding studs, or web stiffener,to make full use of the performance of concrete material, improve the composite action of steel and concrete and enhance the overall effect of the beam. Through column stirrup densification above and below the beam or increasing the column section of the novel joints can not change the the local failure modes. However through extended face bearing plates, or web stiffener of the novel joints can change the the local failure modes, Through comparative analysis of the failure process and bearing capacity of these two types of joint details, it is recommended to use extended face bearing plates.Although column stirrup densification could not change the the local failure modes, but it have a big influence on the bearing capacity and ductility after peak load. Therefore,this article proposes the use of extended face bearing plates and column stirrup densification to the novel composite RCS joint.Finally, combined with the existing theoretical results and the finite element simulation results of the mechanism of the stress of the joint, the bearing capacity formula of the novel composite RCS joints was established. The proposed formula was verified by the finite element simulation and calculation analysis.