Experimental study of various stiffened openings

Abstract

Openings in the web of steel beams have a growing use in steel and composite structures. However, in some cases, the presence of large web openings reduces significantly the beam strength, especially in areas of high shear or when a local force is being applied at the location of an opening. As a consequence, steel manufacturers often need to weld stiffeners to reinforce the openings. The actual European design rules do not provide design guidelines for those stiffeners. However, previous design codes, such as the ENV version of the Eurocode, propose some limitations. An example of limitation is to not consider the stiffener additional section in the bending strength of the opening member in the case of a single sided stiffening configuration. However, it could be observed that this kind of limitation can be very conservative. Thus, two experimental test campaigns have been led in order evaluate the behavior of openings with stiffeners. Different stiffening configurations have been tested and evaluated regarding the opening member deflection, strain distribution and strength. The first campaign consists of testing a beam with a rectangular opening in three points bending. Those tests allow the observation of the Vierendeel mechanism and its reinforcement provided by various stiffening configurations. The second test campaign is dedicated to the study of openings loaded directly on the upper member. Those tests allow the comparison of the mechanical behavior between various opening shapes and stiffening configurations under local load.