الفهرس 
AbstractOnly 14 pages are availabe for public view
 |  | from | 244 |  |  |
| | | from | 244 | | |
Abstract
Built-up cold formed steel (BCFS) columns are used in various engineering structures and installations, such as towers, bridges, fences, and buildings. These sections are made of several precision-fitted metal parts that are either electro-welded or cold-rolled. These columns are characterized by their strength, rigidity, and resistance to external loads, which make them ideal for use in engineering structures that are subject to difficult conditions or require strong support. BCFS columns are of great importance in civil and structural engineering, as they are widely used in the construction of towers, bridges, high-rise buildings, and other engineering structures. These columns help to reduce the weight of engineering structures, improve material utilization efficiency, and reduce construction and maintenance costs. The focus of this research is to investigate the behavior of built up cold formed steel columns. The research presents two creative BCFS columns with varying cross-sectional geometries. Each section is composed of two vertical elements (Sigma sections) back-to-back separated by a distance, connected with two horizontal elements channels and/or plates joining between the vertical elements. Bolts are used to assemble the elements of each sections’ components together. The channel and also the sigma thicknesses are chosen 4 mm while the thickness of the plates is chosen 6 mm . The verification of finite element models simulating BCFS columns subjected to axial compression loading is performed using the finite element software ABAQUS. Then, a new finite element model was introduced to simulate and investigate the behavior of BCFS columns with a various shapes subjected to axial loading through numerical analysis. A parametric study was performed to investigate the effect of different design parameters, such as the length and width of columns, the configuration of the built-up sections, and spacing between connectors, on the performance of BCFS columns, using the finite element software ABAQUS. It was concluded that, the spacing between the bolts did not have a significant effect when local buckling control the failure of specimens. The spacing between bolts was pronounced in case of using cover plate, this is because flexural buckling of plate section between the bolts occurred. Axial Load capacity is directly proportional to steel yielding strength, CFS thickness (t) and the cross-sectional area of different profiles. Axial load capacity of short columns is greatly affected by the stiffened element within the cross section, increasing the stiffeners through the web and the flange significantly increase the axial load capacity. Axial load capacity is inversely proportional to the vertical spacing between fasteners; this effect is more significant with section profiles containing cover plates. These conclusions give encouragement to expand the use of CFS section in more structures type other than light loaded structure only.