This paper discusses the nonlinear behaviour and design of a double track open timber floor plate girder railway deck steel bridge. A 3-D finite element model has been developed for the bridge, which accounted for the bridge geometries, initial geometric imperfections, material nonlinearities of the bridge components, bridge boundary conditions, interactions between bridge components and bridge bracing systems. The simply supported double track railway steel bridge has a span of 30 m, a width of 7.2 m and a depth of 3.12 m. The bridge components comprising main plate girders, stringers, cross girders, connections, bracing members, stiffeners, bearings, and filed splices were designed following the design rules specified in the European Code for steel bridges. The live load acting on the bridge was Load Model 71, which represents the static effect of vertical loading due to normal rail traffic specified in the European Code. The finite element model of the double track bridge was developed depending on additional finite element models, developed by the author, for small and full-scale plate girder steel bridge tests previously reported in the literature. The small and full-scale tests had different geometries, different boundary conditions, different loading conditions and different failure modes. Failure loads, load-mid-span deflection relationships, failure modes, stress contours of the double track bridge as well as of the small and full-scale tests were predicted from the finite element analysis and compared well against test results. The comparison with test results has shown that the finite element models can be effectively used to provide more accurate analyses and better understanding for the behaviour and design of railway steel bridges. The paper presents a complete piece of work regarding the finite element analysis and design of railway steel bridges, which can be used for further parametric studies, finite element analyses and investigations of the bridges under different loading and boundary conditions. The study has shown that the design rules, loading and recommendations specified in the European Code provide accurate and conservative estimations for the design of railway steel bridges.