Research On The Bearing Capacities Of Multi-planar KKT-Joints

Multi-planar tubular structures have advantages of good mechanical properties, beautiful appearances and relatively low costs, they have been widely used in mechanical engineering, civil engineering, and etc. Multi-planar KKT-joints are one of the main types of the structures, they are usually used in the area where primary and secondary trusses are intersected or out-plane braces are supported. And multi-planar KKT-joints are widely used in many gymnasiums, exhibition halls, railway stations and so on. However,current regulations and materials haven’t been dealt with the problems about the bearing capacities of multi-planar KKT-joints. It’s necessary to further study and analyze the static bearing capacities.Refer to the test model of Document [45], and combine with multi-planar KKT-joints in practical engineering and the requirements of joints’ construction in GB50017-2003, the FEA models of the joints are constructed, and the bearing capacities of the joints are analyzed and studied comprehensively.Firstly, the geometric model selection, the types of elements, the properties of materials, meshing generation, boundary conditions, the forms of loading, solution setup,the convergence criteria, the determination criteria of the ultimate bearing capacities of the joints are considered based on the nonlinear finite theory while the flexibility analysis by FEA theory is used in modeling of multi-planar KKT-joints. Then the FEA model is constructed by ANSYS software. And use the FEA modeling methods to certify the test model of Document [45], the results show the FEA models of the joints and the simulation methods adopted by this paper can correctly simulate the bearing capacities of the joints.Secondly, the parametric analysis by FEA methods is used in the bearing capacities of multi-planar KKT-joints. The main failure modes of the joints are determined,the stress distributions and related static properties in the intersection of the joints aredemonstrated. And then the research focus is to study the influences of some important geometric parameters and load parameters on the ultimate bearing capacities of the joints.The results show β1, β2, γ, θ1, θ2 are main geometric parameters which have effects on the ultimate bearing capacities Pu of the joints, but τ1, τ2, L have less effect on on the ultimate bearing capacities Pu of the joints; P,KKTn are main load parameters which have effects on the ultimate bearing capacities Pu of the joints.Thirdly, the calculation formula proposed of the bearing capacities of multi-planar KKT-joints is deduced, which is multiplied by a correction factor based on the design formula of the bearing capacities on multi-planar KK-joints or planar T-joints in GB50017-2003 by the methods of LS. And then the calculation formula proposed is tested with linear regression.Finally, the research results are summarized, reasonable design methods,suggestions and measures are put forward to deal with the problems about the calculations,analyses and design of multi-planar KKT-joints in practical engineering. Then some prospects in the further research are concluded, and some problems to be further discussed are proposed.