Longitudinal Analysis of U-Shaped Girder Bridge

The concept of U-shaped bridge girder is now being increasingly adopted in urban metro rail projects and for replacing old bridges where there is a constraint on vertical clearance. These bridge decks are commonly designed in practice using simplified methods that assume beam action of the webs in the longitudinal direction and similar flexural action of the deck slab in the transverse direction. However, such assumptions can lead to errors. This paper attempts to assess the extent of error in the simplified analysis, by comparing the results with a more rigorous three-dimensional finite element analysis (3DFEA). A typical prototype railway bridge girder has been taken as a case study. The results of the 3DFEA, in terms of load-deflection plots, have been validated by field testing. It is seen that simple beam analysis generally predicts good results, except for some local stress concentrations. Deformation increases as span increases and results are validated with both methods SBM and FEM.