Experimental Study And Theoretical Analysis On Static And Dynamic Performance Of Joint Between Concrete-filled Square Steel Tubular Column And Composite Beam With U Shape Steel Plate Encased Concrete

The composite beam with U shape steel plate encased concrete is a new type of composite structure. It is formed by U shape steel beam filled with concrete. The essential connectors are designed to ensure the combined action. This kind of composite beam has much advantage over other composite beams, such as steel-saving, good stability, large stiffness and higher bearing capacity. Moreover this type of composite beam avoids many disadvantages of other composite beams and will become a kind of composite component having broad prospect for application. Therefore, the study on the composite beam is important in both theory and application. Researches on the joints of composite structure are not detailed; especially there are many differences in choosing the stress and strain relationships of materials and the properties of materials. Based on the full size model test and theoretical analysis, this research investigates the seismic behavior of the joint between concrete-filled square steel tubular column and composite beam with U shape steel plate encased concrete under cyclic load. The main work and achievements are as follows:In order to investigate static performance on the joint of composite beam and column, the failure mechanism and mechanical characteristics of this composite beam are discussed based on the experience of previous experimental and theoretical analysis. The flexural capacity under negative moment and shear bearing capacity under negative moment are discussed with emphasis. The computational formulas of two kind of aforementioned bearing capacity in limiting state are provided. According to check calculation, the ultimate flexural capacity under negative moment is main determinant to the static performance of the structural member.In order to investigate dynamic performance on the joint of composite beam and column, an experiment study was carried out on the joint between concrete-filled square steel tubular column and composite beam with U shape steel plate encased concrete under cyclic load. The experiment process and feature of each specimen are described and load-carrying capacity, ductility, energy dissipation, rigidity degeneration are analyzed. The experiment results verify that this composite beam has much advantage, but the ability of energy dissipation is not strong. Finite element models involving geometric nonlinearity, contact problems between the steel and the concrete and materials nonlinearity are presented. Nonlinear finite element analyses of joint of the composite structure are conducted under low-reversed cyclic loading. Stress distribution in the joint panel zone and the failure mechanism is accurately simulated. The results such as the stress distribution and ultimate bearing capacity of the structure are obtained. Finally, the entire force-displacement curves are obtained by the whole nonlinear analysis of composite frames subjected to cyclically loads. Comparing with the results of test, the results of finite element analyses agree well.