Behaviour of hybrid steel beams with closely spaced web openings
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ORIGINAL PAPER
Behaviour of hybrid steel beams with closely spaced web openings Rujuta A. Bhat1 · Laxmikant M. Gupta1 Received: 1 May 2020 / Accepted: 20 August 2020 © Springer Nature Switzerland AG 2020
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. Keywords Finite-element method · Hybrid steel beams · Web openings · Local buckling
Introduction A hybrid steel beam is generally used in construction where a rolled section or a regular plate girder is not enough to carry the load or is not economical. There is a liberty to choose the size and grades of the steel plates based on the loading requirements. Hybrid steel beams have stronger steel in flanges than web. It is an established fact that hybrid steel beams are economical in comparison to the homogeneous beams, and since 20–25% of the bending resistance of beam can be attributed to the web, a reduction in the steel grade of sweb would only cause a very small loss in beam capacity (Kulkarni and Gupta 2018). New methods are proposed (Shokouhian and Shi 2015; Greco and Earls 2003; Frost and Schilling 1964) for the determination of strength of hybrid beams via experimentation and numerical analyses and simplified formulae for bending resistance are given (Veljkovic and Johansson 2004). Stronger flanges result in reduced ductility of the * Rujuta A. Bhat [email protected] 1
Department of Applied Mechanics, Visvesvaraya National Institute of Technology, South Ambazari Rd, Ambazari, Nagpur, Maharashtra 440010, India
member which is affected by the ultimate to yield stress ratio of the steel (Wang et al. 2016). To validate the behaviour of hybrid beams fabricated using lower grade steel, experiments were conducted on three hybrid girders (Kulkarni and Gupta 2018), and it was found that the flexural strength and ductility for hybrid beams can be improved by providing lateral bracing near to the p
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