The Stiffness Of The Beams Line The Experimental Study And Theoretical Analysis Of The Impact Of The Seismic Performance Of Composite Frame

Linear stiffness ratio of beam to column is an important parameter to reflect the interaction between beam and column. Reasonable linear stiffness ratio can increase the lateral stiffness of the structure and make structure a good seismic performance. This paper focuses on seismic performance and restoring force model of composite frame, which is composed of concrete filled steel tubular (CFST) column and steel-concrete composite beam. To study the influence of linear stiffness ratio of beam to column, both theoretical analysis and experimental research method are used. The main achievements can be summarized as follows:(1)Taking linear stiffness ratio of beam to column as the main experimental parameter, pseudo-static tests were carried on three frame models with different linear stiffness ratio of beam to column, which are single span and single story frame. The experimental research focused on failure modes, hysteretic loop, skeleton curve, displacement ductility, stiffness degradation, strength degradation, energy dissipation capacity and so on, and investigated impacts which linear stiffness ratio have on seismic performance of composite frames.(2)Based on plane-section assumption and chosen stress-strain relationship of material under cyclic loading, a numerical analysis method-called section and layer divided method, was proposed and a FORTRAN procedure was designed to calculate skeleton curve and hysteretic curve of composite frame. The calculation results are verified by comparing to the experimental results, so the calculation method put forward on this paper is reasonable.(3)According to pseudo-static test results of seven composite frames, an analysis was made about influence which axial compression ratio, slenderness ratio, linear stiffness ratio have on the skeleton curve of composite frame; a skeleton curve model is put forward taking the influence of these parameters into consideration, and the skeleton curve model agree well with the curve of test result. (4) Based on pseudo-static test results of seven composite frames, by means of regression analysis, stiffness degradation formula of composite frame was obtained. Once determining the hysteretic path, restoring force model of composite frame is proposed. Comparing with test results, restoring force models proposed in this paper were well agreed with test results.