Date

2013

Author

Çarbaş, Serdar

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Thin-walled section is the one which is made of thin plates. The thickness of thin plates is quite small compared to other cross-sectional dimensions as well as overall length of the member or substructure. Elements made of thin-walled sections are used extensively in steel and concrete bridges, ships, aircraft, mining head frames, and gantry cranes. One common feature of these members made of thin-walled sections is that they are very light compared with alternative sections and, therefore, they are used extensively in long-span structures where the economy is of prime consideration. Thin-walled sections may have a closed or open form. The open thin-walled sections possess small torsional rigidity and they undergo warping deformation when subjected to torsional moments. The warping deformation in turn generates significant normal stresses that are to be considered in the design of such sections. In this thesis, at first an optimum design algorithm is developed for thin-walled beams with open sections when they are subjected to bi-axial bending and torsion. The dimensions of thin plates joined together to constitute the thin-walled section including their thickness are taken as design variables. The displacement, stress and local buckling constraints are considered in the formulation of the design problem. Vlasov’s theory is used to calculate the normal and shear stresses that occur due to warping. Besides, this study also aims to produce optimum design of cold-formed thin-walled open sections and optimum design of steel frame made of these kinds of sections given in AISI-LRFD. For this purpose, a different optimum design algorithm is developed which imposes the behavioral and performance constraints in accordance with AISI-LRFD. Moreover, due to the slenderness and the presence of imperfections in cold-formed thin-walled open sections and steel frames built up with these sections, it is necessary to take cognizance of the geometric nonlinearity into account in the prediction of their response under the external loading in both cases. Afterwards, the optimum design problems obtained turn out to be mixed integer and discrete programming problem. Artificial bee colony algorithm is used to obtain their solution. This technique is a recent numerical optimization technique which mimics the intelligent behavior of honey bee swarm. The recent studies with the artificial bee colony method have shown its effectiveness and robustness in finding the optimum solution of combinatorial optimization problems. Number of design examples is included to demonstrate the competence of the optimum design algorithms developed.

Subject Keywords

Thin-walled structures., Steel framing (Building)., Cold-frames., Steel, Structural., Steel joists., Structural frames.

URI

http://etd.lib.metu.edu.tr/upload/12616585/index.pdf
https://hdl.handle.net/11511/22899

Collections

Graduate School of Natural and Applied Sciences, Thesis