Experiment Research For Composite Simply Supported Beams With U Shape Steel Plate Encased Concrete And Composite Frames

The composite beam with U shape steel plate encased concrete is a new type of composite flexural component. It is formed by U shape steel beam filled with concrete which is welded by C or Z shape cold-formed sheets and a thick steel plate. The essential connectors are designed to ensure the combined action. This composite beam has much advantage over other composite beams, such as higher bearing capacity, smaller deformation, and convenient construction etc. 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. The composite beam with U shape steel plate encased concrete has been researched systematically in this paper. The main work and achievements are as follows:1. The research on mechanical performance of the composite beam with U shape steel plate encased concrete(1) The failure modes, load-deflection curves, load-strain curves, the distribution of strain along the height direction of beams are analyzed from the static test of fourteen simply supported specimens. The mechanical performance of the composite beam with U shape steel plate encased concrete is realized preliminary and the essential measures ensuring steel and concrete work together are determined.(2) The failure mechanism and mechanical characteristics of this composite beam are discussed through theoretical analysis and FEM analysis validated by the result of test. Two particular kinds of failure mode of the composite beam with U shape steel plate encased concrete are discussed with emphasis, which are the longitudinal oversize slip failure and the longitudinal horizontal shear failure. And the effect of the form of U shape steel beam top flange on mechanical behaviors of composite beam is researched. Finally, it is pointed out that the flexural capability of composite beam is computed with consideration of the effect of slip between steel and concrete. However, the deflection of composite beam on normal usage is computed without consideration of the effect of slip sometimes.(3) The complete design methods for the composite beam with U shape steel plate encased concrete are provided on the foundation of test research and theoretical analysis, including the construction stage and the usage stage. For the usage stage, the computational formulas of four kind of bearing capacity in limiting state and the computational formula of deflection are provided.2. The research on seismic performance of composite frame having the composite beam with U shape steel plate encased concrete(1) The mechanical behavior of the composite beam is researched in whole frame structures through the seismic test of two composite frames having the composite beam with U shape steel plate encased concrete. The failure modes, failure mechanism, seismic ductility, dissipation of energy, the ability of deformation retrieval and the bearing capacity and so on are analyzed. It is found that the basic principles such as strong connecting and weak component failure mechanism and strong column and weak beam failure mechanism demanded by seismic design can be realized by feasible design.(2) The plastic-elasticity analysis of composite frame having the composite beam with U shape steel plate encased concrete is carried through by FEM analysis software under monotonic load. The crack load, thedistribution of crack, ultimate bearing capacity, the distribution of stress of steel component and so on are obtained and are compared with the results of test and the relevant analysis. Finally, the entire force-displacement curves of composite frames are obtained by the whole nonlinear analysis of composite frames subjected to cyclically applied lateral loads or displacements. Comparing with the results of test, it is proved that the entire procedure of loaded structures can be simulated very well by commercial software. (3) A new type of connecting of column and beam is designed. The design methods for the composite beam with U shape plate encased concrete connecting with RC column or SRC column are unified through placing H steel in connecting. Stiffening rib and shear plate are welded in H steel. The results of tests and FEM analysis prove that stiffening rib and shear plate may well transfer shear jointly with the web of H steel.This paper can provide scientific verifications for the establishment of national engineering construction standard entitled'The code of design and construction for composite beam with U shape plate encased concrete and floor'.