Experimental Study On Bearing Capacity And Failure Mechanism Of Improved Composite Steel Staggered Truss Structures

The steel staggered truss system is a new concept in structure steel framing for high-rise buildings. It is characterized by economy, efficiency and practicability and it has drawn wide attention in both engineering and academic field recently. Steel staggered truss system performs excellently under earthquake, but its application is very rare in our country due to the lack of research on its seismic performance. As a part of study of "Development of Application Technology of Staggered Truss System" sponsored by special fund for technology development projects of Ministry of Science and Technology, this paper presented analytical and experimental study on seismic behavior of an improved composite steel staggered truss structures. The selections of these subjects have a great theoretical significance and engineering value.Based on the demand of cycle-loading experiment study of this new type structure of the project, one-third scale specimen of five story improved composite staggered truss structures was designed in this paper according to similar theory and relevant codes, including the design of global structure, joint design and the detail drawing.The specimen model was analyzed by finite element program ANSYS, in which Shell 181 element was adopted and t material nonlinear and geometric nonlinear were considered. After elastic-plastic analysis was carried out, the stress-strain distribution, bearing capacity and deformation patterns in different loading history were provided. According to the results of the finite element analysis, the experimental scheme of specimen was developed, including loading history and layout of stain gauge.Based on a quasi-static test of the one-third scale model of five story improved composite staggered truss structures, the bearing capacity, hysteretic characteristics, ductility and performance of plastic deformation, stiffness deterioration, the properties of seismic energy dissipation and failure mechanism of the structure were analyzed. Also, according to hysteretic curves of the top storey, the corresponding skeleton curve and restoring force model of the structure were obtained. The result showed that the load-displacement hysteretic curve was a shuttle shape which was stable and fullness, and so did the ductility and ability of deformation, energy dissipation and bearing capacity. Since the lateral stiffness and bearing capacity is provided mainly by the truss, the damage of the diagonal bar in the truss means structural failure. So the width-to-thickness ratio should be strict for the ability of plastic deformation. At least, they should comply with the demand of brace in concentrate braced frame. The weak storey of the structure was transferred from the bottom and the upper storey before improvement to the other. This satisfied the purpose of improving and provided important test data for the further work.