Force mechanism and nonlinear finite element analysis on the behavior of CFDSST column-to-beam connections
Bin Chen School of Resources and Safety Engineering Central South University, Changsha, Hunan, P.R. China
ABSTRACT: To study the mechanical properties of concrete-filled double skin steel tubular (CFDSST) column-to-H-beam connections assembled by T-stubs and high strength bolts, the research parameters are the thickness of T-stub flanges and webs and the diameter of bolts. In the paper, the forces mechanism analysis of composite joint under the antisymmetric loads at the cantilever end of H-beam, and the axial load at the top of CFDSST column, are presented. So the potential theoretical failure modes are found. To validate the theoretical results, the nonlinear finite element (FE) analysis on the behavior of CFDSST column-to-beam connections is conducted using the software ANSYS11.0. The analytical FE models take into account geometrical discontinuities, material nonlinearities, large displacements and contact problems. The results indicate that the FE method can effectively estimate the failure modes of composite joint, and the FEmodels results are good agreement with the theoretical ones. The thickness of T-stub flange and the diameter of bolt can markedly influence the carrying capacity of joint, but the thickness of T-stub web influences less. The FE model results also present that the theoretical carrying capacities of T-stub analogy calculated by Eurocode 3 are conservative, leading to limitation in predicting values for strength and stiffness of the connections. The tensile T-stub flange is in bidirectional flexural condition, to improve the whole mechanical performances of joint, the thicker T-stub flange should be adopted.