الفهرس 
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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.