Comparative analysis of load-bearing capacity of corrugated steel web beams in trapezoidal and sinusoidal form

In steel I-Section beams, the web element carries the compressive stress caused by the loads and transmits the shear forces within the beam, while the flanges respond to the external loads to the beam. Considering material saving and load-bearing capacities together, the principle of the delicate web against thick flanges is adopted for these beams. In this case, compressive stress on thin and flat bodies due to overloads cause loss of beam stability and large deformations. The corrugated web beams can be designed to be joined with the upper and lower flanges which are made of the corrugated sheet with a thin cross-section and which are steel plate with the same material properties as the web. The corrugated web beams prevent large deformations and loss of stability; they prevent the beam from losing stiffness before it reaches the plastic limit under load combinations applied; they prevent buckling and increase the load-bearing capacity of the beam against local buckling by shear forces. This curved structure of the beam web reduces the beam's own weight and increases its load-bearing capacity. These beams, which have been used effectively in developed countries in recent years, can be used effectively in roofs as an alternative to the space frame systems and truss systems which are commonly preferred in Turkey, floor beams or as columns under normal force effect. Initial studies on corrugated web beams focused on trapezoidal troughs. Elgaaly et al. investigated the collapse failure conditions of these beams caused by shear (1996) and bending (1997) under different load conditions. As a result of these studies, they suggested that the slender web can be neglected in bending design due to the insignificant effect on the load-bearing capacity of the beam. It was investigated by Johnson and Cafolla that collapse conditions due to shear and bending depend on the position of the loads and the trapezoidal structure of the corrugation (1998). In the experimental studies performed by Li et al., the trapezoidal web beams have been found to have 1.5-2 times more buckling resistance compared to flat web beams (2000). The fact that buckling strength in thin web thicknesses of corrugated web beams is comparable to beams with flat and higher web thickness was investigated by Pasternak et al. (2010). In the studies mentioned above, always the constant parameters related to the web structure of the beam have been used. During the design within this project, thickness and depth parameters of corrugated web structure and flange thicknesses will be evaluated in terms of cost and taken as design variables according to optimization principles. The proposed research thesis is planned to consist of three parts. In the first part, the optimum dimensioning of the sinusoidal and trapezoidal beams will be made by using new optimization methods such as to minimize its weight. Web height, plate thickness, the distance between the peaks of trapezoidal and sinusoidal webs, flange width and thickness in construction beams with corrugated web beams were also accepted as design variables. With these parameters, values that will minimize the beam weight under the behavior and geometric limiters will be obtained. The solution of formulated structural optimization problems will be obtained by adaptation of firefly algorithm, which is one of the new optimization techniques, and the performance of the method in finding the minimum weight of the beam will be examined. In the experimental process which is the second and main phase of the study, in the first section, spread and two-point loading strengths of the optimized corrugated web beams with sinusoidal web and optimized corrugated web beams with trapezoidal web designed in the best way to the geometric form of the sinusoidal web structure will be tested by using a load frame with pressure cylinders having hydraulic power unit. In the third and final part of the thesis, web plate buckling analysis of corrugated steel web beam samples and calculation of critical loads they can bear will be carried out by using finite element program and finite element analysis results recorded for each different web thickness and length will be compared with the data obtained from the experimental study. The corrugated web beams will be designed considering the design criteria specified in BS EN 1993-1-5: 2006 (Annex D, Eurocode 3) and DIN 18-800 Part-1, Part-2 specifications. With the results obtained, it is aimed to determine how to make the optimum design of corrugated web beams for which collapse situations under load differentiates from standard I-section profiles and whose designs cannot be made by ordinary analysis methods; also it is aimed to ensure that it is preferred in buildings in Turkey.