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Thesis (M.Eng.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 168-170.

Stainless steel has garnered attention as an alternative structural material to conventional carbon steel due to its corrosion resistance properties and aesthetic appearance. Of interest are single angles, which are frequently used in trusses, transmission towers, and as bracing diaphragms. When subjected to compression, knowledge concerning the behavior, analysis, and design of stainless steel single angles is very limited. This thesis addresses the behavior of duplex stainless steel single equal-leg angles subject to concentric compressive loading. Two complementary approaches are used in this study, the first of which was experimental and consisted of conducting 33 full-scale buckling tests on S32003 duplex stainless steel single equal-leg angle components. Angles specimens had slenderness ratios ranging from 35 to 350 and leg width-to-thickness ratios of 7.5 to 12.3. In the second approach, computational models that accounted for material nonlinearity, material anisotropy, and geometric out-of-straightness were developed and validated using the experimentally obtained test results. These models were subsequently used to perform numerical buckling experiments to shed light on the behavior of axially loaded compression duplex stainless steel single angles for a wide range of practical leg width-to-thickness ratios. Results from the full-scale tests and from the numerical models are shown to correlate well with the classical mechanics-based formulae, which considers nonlinear stress-strain relationships, for predicting flexural and flexural-torsional buckling strengths of singly symmetric stainless steel members. Finally, design criteria in the form of load and resistance factor design (LRFD) with a reliability index of 3 for buckling limit states are proposed for possible adoption in future US national standards.

M.Ing. (Civil Engineering) / Cold-formed steel lipped channels are among the most used sections, as framing members in the building construction industry, especially in residential, commercial and industrial buildings. In portal frame, when lipped channels are used as main frame members, they are usually restrained from the top flange through angle-cleat to prevent lateral-torsional buckling. This restraining system works together with an additional restrain system called fly-bracing. Drilling a bolt-hole or welding the angle cleat onto the flange of the main frame weakens its bearing length. Additional disadvantage of this restraining system is the fabrication costs of providing fly bracing. However, past research into lateral-torsional buckling of cold-formed steel lipped channel sections are limited. Therefore this study investigates a restrain that avoids bolt holes and welding in the top flange of the rafter, and the use of fly bracing. In the first phase of this research, tensile coupon tests of the three cross-sections are conducted to obtain the material properties. The elastic modulus and yield strength of the cold-formed steel used are determined from stress-strain relationship. These properties are used to calculate the code-predicted lateral-torsional buckling moment resistance. The second phase of this study involves a series of experiments on the lateral torsional instability of single cold-formed channels. The channels are restrained by a purlin – angle cleat connection and are subjected to a two point loading system in order to simulate a distributed load. Failure of the channels occurred by local buckling of the compression zone of the flange and web and lateral torsional buckling of the channels between points of lateral support. Tests have shown the purlin – angle cleat connection to be capable of restraining the frames from failing due to lateral-torsional buckling. This eliminates the idea of using fly-bracings, as is normally done in practice to restrain torsional instability. The results from the experimental study do agree well with those predict by the South- African code, SANS 10162-2: 2005. This research presents the details and results of the experimental study including a comparison of results with the South-African code SANS 10162-2: 2005 predictions. It also presents the recommendations made regarding the use of a numerical model study in order to compare the results with those from the experiments.