الفهرس | Only 14 pages are availabe for public view |
Abstract This thesis presents a novel technique to improve the performance of steel space trusses with the composite action method. Steel space trusses are widely used for covering large areas and carrying heavy loads, but they often fail due to brittle failure in the compression members. To overcome this problem, this study proposes to replace the hollow circular steel tubes with Concrete-Filled Steel Tubes (CFST) in the compression members. CFST members have shown to have high axial compression strength and ductility by combining the advantages of steel and concrete sections. The thesis consists of two parts: an experimental program and a numerical analysis. In the experimental program, the behavior of slender hollow steel and CFST columns under axial loading is compared and the behavior of a full-scale space truss with CFST members is examined. In the numerical analysis, the experimental results are validated and the effects of various parameters on the behavior of space trusses with CFST members are investigated. The study also presented a detailed validation process of the CFST element and space truss using finite element analysis. The validation process involved several steps, such as defining the geometry of samples, material modeling, part type, mesh size, and boundary conditions. The validation process aimed to capture the linear and nonlinear buckling failure modes of the CFST element and space truss. The study further conducted a parametric study using finite element analysis to explore the behavior of composite space trusses made of CFST members. The parametric study modeled real fully-scaled space trusses covering large areas with variable cross-section members and buckling ratios. The parametric study examined different modes of shape for members under various loading conditions. The results of the finite element analysis, such as ultimate load capacity, load-axial shortening curves, and deformed mode shapes, were presented and discussed. The use CFST elements instead of hollow steel elements in space trusses increased the ultimate load capacity and reduced the steel consumption in the construction of space trusses. CFST and hollow steel members had the same deformed shape at the failure due to compression or brittle failure. The finite element model showed excellent agreement with experimental results. |