Experiment And Analysis On Spatial Tubular Joint Reinforced With Plate

The bearing capacity design of joints in spatial steel tube structure is one of the important steps to consider in the design of such structures.At present,the research on steel tubular joints at home and abroad mostly focuses on planar joints and simple regular spatial joints.However,the research on complex spatial joints is rather rare.And this kind of joint usually uses the structure of the outer plate to improve the mechanical behavior of the joint.However,there is no corresponding design method for its capacity at present.To promote its application in engineering,it is necessary to study the influence of such kind of joints on its bearing capacity.In this paper,taking the super high rise building project of Chengdu Greenland aircraft school as the background,the static bearing capacity test of the 1:2 scale model under the design load is carried out on the two reinforced key joint in the project.The test results show that the bar intersections of the joint have greater stress than other parts,and the plate have improved the stress concentration in this part.The joints are in the elastic stage under the design load,and the design of the joints is safe and reliable and has a large safety reserve.After that,this paper uses ABAQUS to simulate the scale test model and the full scale model of two key joints.The comparison between the results of each bar's stress distribution in the test and in the finite element calculation verifies the rationality of the finite element model.The axial force and stress distribution of the joint members in the finite element model are coincident with the test results.In order to find the failure mode of the joint,the elastic-plastic analysis of the joints by ABAQUS shows that the failure modes of the two joints are brace failure.A1 joint?with plate?bending failure for bar 8 and bar 12,A1 joint without plate failure to bar 12 bending failure.Although the plate does not significantly improve the bearing capacity of the joint,it has slowed down its bearing capacity's decrease.A2 joint?with plate?is local buckling failure of bar 8.The main bar of No.5,No.9 and No.10of A1 joint form a T-joint with plate.In order to master the bearing capacity of this kind of joint,the ABAQUS FEM parameter comparison analysis was carried out for the joint with or without plate.The parameters include?the diameter ratio between chord and brace,?is the diameter thickness ratio of the chord,?is the thickness ratio between chord and brace,l/d₀ is the ratio between plate length and the chord diameter,t/t₀ is the ratio between plate thickness and the chord thickness,h/d₀ is the ratio between plate height and the chord diameter.The results show that the length of the plate has great influence on the bearing capacity of the joint,and the thickness and height have relatively little influence on the bearing capacity of the joint.The plate does not significantly increase the bearing capacity of the test joint?the chord diameter is equal to brace diameter?,but significantly improves the bearing capacity of the T joint with a larger diameter of chord?0.2<?<0.6?.Based on the analysis of finite element parameters,a method for calculating the bearing capacity increasing coefficient?which is plate-reinforced joint's bearing capacity divided by ordinary joint's bearing capacity.The improvement coefficient of the A1 joint is in good agreement with the finite element analysis results.This method can provide reference for the calculation of the bearing capacity of the T joint in the project.