Post Local Buckling Behavior and Ultimate Capacity of H–section Beam
Abstract This paper presents a study on the ultimate capacity (maximum strength and plastic deformation capacity) of a thin–walled H–section beam. An experimental study is adopted by subjecting beams under cyclic loading to a large range of deformations with large depth–thickness ratios, which are over or close to the limit value of the current standards. The objectives of the present paper are to reveal the post local buckling behavior and to propose a handy method to evaluate the ultimate capacity. Instead of the commonly used parameter of width and depth–thickness ratio, the normalized thickness ratio WF developed in this study based on the author's previous studies can be regarded as the major parameter to evaluate the ultimate capacity. The relationship between WF and ultimate capacity is examined. The improved criteria for assessing the maximum strength and plastic deformation capacity of an H–section beam is proposed using normalized thickness ratio WF and is shown to be in good agreement with the experiment results.
Ultimate capacity of I-slender section columns
Abstract The design provisions in most codes of practice usually use the concept of effective width to account for the presence of local buckling when calculating the ultimate capacity of slender sections. The expressions used to calculate this effective width are function of many variables. One of these variables is the state of stress within the section. This state of stress is usually calculated from the ultimate strength curves of compact sections based on the member slenderness ratio only. In this paper a non-linear finite element model is made to investigate the variation of this state of stress along with flange and web width–thickness ratios of slender I-sections for different member slenderness ratios. A group of slender I-sections that varied in their flange and web width–thickness ratios are chosen. A wide range of column slenderness ratios is selected to draw complete ultimate strength curves. Results show that the ultimate stress greatly depends on the interaction between the flange and web width–thickness ratios as well as on the member slenderness ratio. The ultimate strength curves are different from those of compact sections especially for members with low and intermediate member slenderness ratios. A proposed strength equation, which is function of the flange and web width–thickness ratios besides member slenderness ratio, is given. Finally, results are compared with the different design specifications.
Behavior and Design of Thin‐Walled Columns
Features of the phenomenon of interactive buckling of thin‐walled columns are briefly reviewed. The theoretical results are compared with the recent test results from University of Sydney and earlier results from Cornell University. The agreement is very good indeed. The role of imperfections in producing scatter in the prediction of the ultimate capacity of the columns is illustrated. Design procedures, one developed at Cornell University in the seventies and the other recommended by the new American Iron and Steel Institute Code, are examined in the light of the new results. In order to account for the interaction of plate elements, it is suggested that exact local critical stress be used in the effective width formula. To obtain a reliable and safe estimate of the column strength, it is proposed that the collapse load given by the design methods be multiplied by an appropriate factor. This factor must be a function of the key parameters governing the problem. A statistically derived expression for this...