Study On Mechanical Behaviors Of Tubular Joints Of Lattice Columns And Tube Trusses

With the improvement of metallurgical technology and steel properties in recent years,more and more steel structural members are used as skeletons in architectural design,especially in the design of super high-rise and long-span buildings.In the design of steel structures,lattice columns and pipe trusses are commonly used component systems.When both lattice columns and pipe trusses adopt circular tubes,their intersecting joints will produce a large number of intersecting arcs,and the stress state is quite different from that of the traditional plane intersecting joints.Based on a large steel structure stadium,the mechanical behaviors of the intersecting joints of lattice columns and pipe trusses is studied by combining finite element numerical simulation with test research.In this paper,the representative intersecting joints of lattice columns and pipe trusses are selected as the research objects from specific engineering cases,and their mechanical behaviors are mainly studied,including bearing capacities,hysteretic curves,ductilities and energy dissipation capacities.Different from previous studies,this paper mainly focuses on the study of the mechanical behaviors of the intersecting joints of lattice columns and tubular trusses under three-dimensional loads or constraints,especially the influence of the non-main direction of the pipes on the joint performance.In the research method,the finite element model which is consistent with the test is established by combining the experiment with the finite element numerical simulation.On this basis,the optimization and expansion are carried out,and two kinds of joint reinforcement models are established.In the aspect of test,based on actual working conditions and constraints,four fullscale specimens are used.According to the comparative analysis of test data,the mechanical behaviors of the joints are summarized.According to the failure form of the joints,the original joints are optimized and strengthened,which improve the mechanical behaviors of the joints and have a certain reference significance for the design of the relevant joints.In the aspect of finite element numerical simulation,ABAQUS is used as the analysis software to define the joint parameters.Combining with the relevant finite element principle and the specific test data,a finite element model which is consistent with the test results is established.It shows that it is feasible to use finite element software to model and analyze the mechanical behaviors of the joints of lattice columns and pipe trusses.In addition,different optimization and improvement designs are adopted for the joints,and the strengthened joints have better mechanical behaviors.Combining the test with the finite element numerical simulation,the following conclusions are drawn in this paper:(1)Due to the use of thick-walled circular steel tubes and large diameter ratio of supervisor and branch,the failure mode of the intersecting joints of lattice columns and trusses is mostly tensile failure of the intersecting welds,and the ultimate bearing capacity is about 1.5 times of the design capacity of the code;(2)The intersecting joints of tubular lattice columns and tubular trusses exhibit certain energy dissipation capacity when the tubular truss supports are subjected to low cyclic repeated loads.However,due to the tensile fracture of welds,their seismic performance and energy dissipation capacity have chances for further improvement;.(3)The finite element software ABAQUS is used to simulate the mechanical behaviors of tubular lattice column and tubular truss joints under low-cycle repeated loading.The model parameters are selected and the simulation results are in good agreement with the experimental results.;(4)By adding stiffened triangular plates and stiffened arc plates,the mechanical behaviors of joints are improved to a certain extent and the stress distribution on the main pipe of lattice column is improved,but at the same time,the stress concentration on the pipe truss support appears.It is necessary to design stiffened triangular plates and stiffened arc plates after considering many factors.