Behaviour of hybrid steel beams with closely spaced web openings

Abstract

In this paper, the behaviour of hybrid steel beams having openings in the web has been analytically studied. Hybrid beams are often used when the design requirement is not satisfied by hot rolled sections or homogeneous built-up sections. Typically, the steel grade in flange is higher than the web. The presence of openings in the web tends to result in different modes of failure such as web-post buckling and vierendeel mechanism. This paper attempts to analyse a hybrid steel beam with hexagonal web openings. The modes of failure of such beams are compared to their homogeneous counterparts along with the load carrying capacity for each. Center-to-center spacing of openings is varied as well as the effect of change in depth of openings is observed in this study. A general observation is made for modes of failure which are found to be very similar for homogeneous and hybrid beams. An optimum ratio of spacing and width of opening is determined to be 1.5 for beams having a depth of opening lower than 60% the beam depth. For opening depths larger than 60%, load carrying capacity is drastically reduced. For spacing ratio below 1.5, web-post buckling is pronounced and the beam does not reach its plastic capacity.