| The concrete filled steel tube composite structure has been developed for more than one hundred years and has been popularized and applied for half a century in China.In this paper,the performance and optimization method of the concrete-filled steel tubular column-steel beam external stiffening ring bolted joint are studied.Based on the existing test data,the finite element model of the node is established and its accuracy is verified.Then,the construction measures to optimize the performance of the node are proposed through finite element parameter analysis.The theoretical calculation methods of initial stiffness and bearing capacity of joints are discussed.Based on the existing test data of joints,three moment-angle curve models of joints are compared.The main research contents are as follows:(1)The finite element model of the concrete-filled steel tubular columns-steel beam external stiffening ring bolted joint under low cyclic reciprocating load is established,which is in good agreement with the existing pseudo-static test results.The finite element calculation results show that the main failure mode of this type of joints is the buckling and large plastic deformation at the interface area between the steel beam and the end of the outer stiffened ring plate,forming plastic hinge.The plastic energy dissipation of the bolted rigid joint is more than 80% of that of the welded rigid joint,and the steel beam is the main energy dissipation component.(2)using the component method related theory,node stiffness model,deduce the concrete-filled steel tube column outside the steel reinforcement ring plate bolt connection node initial stiffness calculation formula,physical meaning is clear,the theoretical calculation results are in good agreement with numerical simulation results,and the initial stiffness and the node during the bending is mainly affected by the components of the initial stiffness of smaller parts.According to different failure modes of the concrete-filled steel tubular column-steel beam external stiffening ring plate bolted joints,the calculation formulas of the flexural capacity of the joints are deduced,and the theoretical calculation results are in good agreement with the numerical simulation results.A total of 61 sets of node data from 17 literatures including this paper were collected to compare the three moment-angle curve models.The dimensionless moment-angle curve model proposed by referring to the true triaxial plastic-damage model of confined concrete was in good agreement with the test curves of welded joints and bolted joints in the ascending and descending sections.It can provide reference for the design of CFST joints. |
