1. The problem statement, all variables and given/known data A railway bridge of 80ft span with two tracks is supported by two main steel girders of I-section. The girders are 7ft deep between the centers of the flanges. If the dead weight of the structure between the abutments is 200 tons and the weight of each train of carriages is 1.5 tonf/ft, what must be the effective girder flange area at the centre of the span? The mean stress allowable in the flanges is 7tonf/in^2 and the resistance of the web to bending may be neglected. 2. Relevant equations I understand the I need to use f/y = M/I and relevant equation for finding second moment of are and bending moment etc 3. The attempt at a solution The problem here with me is that I cant get to understand the question properly. To much stupid explanation. Its all ambiguous. Like how are the tracks supported by beams ? Are beams in the same direction as the tracks or are the perpendicular ? And isn't the area supposed to be constant throughout th girder ? What is meant by this "what must be the effective girder flange area at the centre of the span" ?