Behavior of intermediate transverse stiffeners attached on web panels

Current AASHTO and AISC specifications require that an intermediate transverse stiffener attached on the shear web panel be designed not only to have a proper bending rigidity to meet the simply supported condition when the web panel buckles, but to have a proper area in order to resist the compression developed due to diagonal tension in the postbuckling range as well. However, the equation for the required areas, which was suggested by Basler in 1963 has been known to be conservative. According to recent studies, Basler's assumption for the formulation of the design equation appears to be questionable. In this paper, the behavior of the transverse stiffeners is investigated through a three-dimensional nonlinear finite element analysis. This finite element analysis gives results that are contrary to Basler's questionable assumption. The transverse stiffener is not necessarily subjected to axial compression in the postbuckling stage, and therefore, the requirement for the minimum areas can be voided. A shear transfer model called "shear cell analogy" is presented in order to describe the postbuckling behavior of the shear web panel in a manner different from those in the literature to date. This analogy is also used to explain why axial compressive stresses do not develop in the transverse stiffeners.