Seismic Performance Of Concentrically Braced Steel Frame With Pinned Connections

The connection design, manufacture and installation are simple and convenient for the hinged joints concentrically braced steel frame with pinned connections. Meanwhile, brace and beam, column using gusset plate connection, not only to transfer power clear, simple structure, has a certain energy dissipation capacity, but also closer to the ends of the hinge and the main axis force. Especially the structure system owns good seismic performance in the high seismic region. But there is no imperfect design terms about the concentrically braced steel frame with pinned connections in Chinese relevant specifications, due to relatively fewer studies about its seismic behavior.In this paper, for the concentrically braced steel frame with pinned connections, the experimental research and the ABAQUS finite element analysis have been carried out to obtain the seismic response, ultimate load and ductility of the structure system; Verifying the reasonability of structural measures of members and connections; Studying the variation rules of the secondary moments on the columns and the beams in steel braced frame; Verifying the impact of distance between the end of bracing member and the assumed line of restraint for the gusset plate. The main contents are listed as follows:Firstly, based on the seismic design method for concentrically braced frame and pinned connections, and the principle of connection stronger than members, one three-story model with 1:4 scale for shaking table test and two three-story models with 1:2.6 scale for pushover test were constructed. A series of factors were considered, including brace slenderness ratio, thickness ratio and clear distance on the gusset plate.Secondly, model for shaking table test was tested by using shaking table under 24 different earthquake ground motions. The dynamic properties, response of displacement and acceleration, the failure modes of structure, the strain data of key connections, and the brace out-of-plane and axial deformation under different earthquakes were studied. Seismic performance of the structure, and the secondary moments on the columns and the beams were analyzed, and seismic design method of pinned connections was verified.Thirdly, with shell elements in Programe ABAQUS, the finite element models of the special concentrically braced steel frame were built up to simulate the test results of shaking table test. The finite element results were compared with the test results so as to analyze their similarities and differences, verifying the reliability of the finite element simulation and providing a basis for analyzing the overall model.Fourthly, a pushover test was carried out to two scaled models of special concentrically braced steel frame. The key responses were obtained, including: the failure mode, the load-displacement curve, the strain data of key connections, and the brace out-of-plane and axial deformation. Based on the test data, analyses about the ultimate bearing capacity of the structure, ductility performance, structural influencing coeffcient, yielding sequence and the secondary moments on the columns and the beams were conducted.Finally, based on previous finite element analysis and experiments about the secondary moments in beams and columns of the beam-to-column hinged joints and braced frame with pinned connections, reasonable values of the secondary moments are suggested for the engineering design of the columns and the beams. Meanwhile, measured values of the experiments in this paper has been used to verify the reliability of the proposed values.