Buckling of T-beams under cyclic bending

This paper presents the results of an experimental study of the response and stability of elastic-plastic T-beams under cyclic pure bending, with emphasis on local buckling. The objectives of the study were to determine the evolution of instabilities and to find parameters useful to determine the degree of damage incurred during cycling. All specimens were subjected to a quasi-static curvature symmetric loading history of constant amplitude. The results indicate that, in the range of curvature amplitudes considered, structural degradation was mainly due to progressive growth of a ripple in the lateral deflection of the web. The unstable growth of one of the features of this ripple led to the formation of a local buckle, which caused a marked reduction in the moment capacity of the specimens. Further cycling resulted in fracture of the web at the local buckle. The best indicator of degradation was a measure of the amplitude of the ripple in the lateral deflection of the web. This measure could be used to generate a criterion for assessing the current state of the specimens in relation to their useful life under cyclic bending. (C) 1998 Elsevier Science Ltd. All rights reserved.