Buckling of T beams under bending

Beams of open cross-section such as I beams, channel sections and T beams are used in many structural applications to resist bending loads. The present investigation concentrates on the elastic-plastic response and buckling of steel T beams under pure bending. The problem is being investigated using combined experimental and numerical approaches. The experiments are conducted in a specially built four-point bending device. The specimens tested have width and depth of 1.5 in. and thickness of 3/16 in. The specimens are loaded in curvature control in order to better identify the instabilities which arise during the bending process. During an experiment, the curvature, moment and cross-section deformation are carefully monitored using appropriate instrumentation. Bending experiments have been conducted for cases in which the flange is in tension or in compression. The moment-curvature responses are somewhat different due to the significantly different mode of deformation of the cross-section. Both lateral buckling as well as buckling of the web have been observed depending on the loading conditions and the length of the specimens. In all cases, buckling was followed by a limit moment in the response of the specimens and finally collapse. A numerical tool to predict the response of the beams hasmore » been developed using a Rayleigh-Ritz-like approach based on the Principle of Virtual Work. The kinematics employed allow deformation of the cross-section. The material behavior is modeled using classical plasticity with isotropic hardening. The material properties were obtained from uniaxial tests conducted on material specimens extracted from the beam. The numerical results agree well with the experimental measurements. The issue of buckling of the beams has also been addressed analytically. Results obtained in this case are also in good agreement with experimental observations.« less