Vrcelj, Zora and Bradford, Mark A (2005) Assessment of Half-through Girder Railway Bridges for Elastic Buckling. In: Australian Stuctural Engineering Conference 2005 : structural engineering - preserving and building into the future : 11-14 September 2005, Newcastle City Hall, Newcastle, NSW, Australia. Stewart, Mark G and Dockrill, Brad, eds. Tour Hosts, Sydney, pp. 251-260.

Abstract

In railway infrastructure, the gr ade is usually predetermined a nd so the design of bridges is constrained to meet the railway grade. Because of this, rail overpass bridges are very often in the form of half-through girders, in which the headroom limita tion requires that the I-section beams that form the half-through girders are loaded at the level of the tension flange, rather than at the compression flange level in more conventi onal bridges. Half-through girder bridges are in general comprised of two parallel I-secti on beams joined by a concrete deck at the bottom/tension flange level as ill ustrated in Figure 1. Loading the beam at the tension flange level through the deck results in the top flange being subjected to compression, and the top flange is not braced against overall buckling. The compression flange of the I-section is restrained only by the stif fness of the usually flexible web and the tension flange is provided with continuous torsional restrain t through its connection to the concrete deck. An arrangement analogous to this one is that of a heavily loaded beam supported on seats (Bradford, 1989).

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