A THESIS SUBMITTED TO THE FACULITY OF CIVIL ENGINEERING, INSTITUTE OF TECHNOLOGY, SCHOOL OF GRADUATE STUDIES, ARBA MINCH UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIRMENTS FOR THE DEGREE OF MASTERS SCIENCE IN STRUCTURAL ENGINEERING.

Abstract

Steel beams are crucial raw materials for the construction industries, the skeletal structure of building or bridge is usually comprised of steel beams to add strength and improve load carrying capacity of the structure. In construction industries, for both strength and aesthetic reasons, structural steel beams are frequently utilized in continuous bridges, framed buildings; towers. There are two main types of structural steel members which are being used in steel structures, hot-rolled steel members and light gauge steel (cold formed steel). This study covers about Hollow flange steel beams which are special cold-formed steel sections made for use as flexural members. Any open sections like channel, zed, hat and others section are susceptible to flexural and torsional failures along its length, when two open sections connected back-to-back that produce the built-up cold formed flat flange conventional sections. In practical framework, the main challenge with using such beams in long span continuous frames is that if the compression flange is unrestrained, the beam section will warp and twist along beam length. So, the understanding how such beams can increases in flexure resistance capacity under static loading, is crucial idea that needed to the use hollow flange beam. Nonlinear finite element (FE) models were formulated and validated with the experimental test results. It was observed that the developed FE models had precisely predicted the behavior of hollow flange beams. Further, the verified FE models were used to conduct a detailed parametric study on cold-formed steel hollow flange beam sections with respect to width, span length, depth, and thickness under static loading. All beams were simply supported and subjected to two-point loading configuration. The ultimate load capacity and failure mode of all beams were determined. The first parameter used in this study was width of top hollow flange, when the sizes of width of compression flange increased the load carrying capacity also increase. Secondly, the depth of section increases with load carrying capacity. Other parameter is thickness of the section, when thickness increases the flexural capacity also increase, finally, when the section is short there is higher load capacity compared to slender section.