Parametric Study On Skew Underpass Bridge

Overhead catenary wires and high level embankments of railways make Railway Over Bridge (ROB) to occupy more space in order to maintain the adequate gradients on the access ramps. Pushing a Precast-concrete box structure using jacks is a preferable solution at such situations. Thus the vehicular traffic is allowed inside the box structure whereas rail traffic goes over the box. Often, construction details call for skew box with railway lines above the box structure that are not necessarily perpendicular to the roadway of the bridge. In design practice, these underpass skew bridge structures are typically analysed as simplified two-dimensional frames. However three dimensional finite element analysis controls the behaviour of skewed structures that a plane frame analysis cannot represent. This paper explains the structural performance of box structure of underpass bridge with varying skew angle, geometric parameters, influence of soil structure interaction and effect of haunch. To understand the behaviour, series of Finite Element Analysis (FEA) were performed using SAP2000 on a number of skew box (skew angles varies from 0o to 60o) underpasses to simulate various geometric configuration parameters. Based on the FEA results, series of correlation diagrams were developed relating the moments and deflections due to dead loads in a skew underpass to those from plane frame analysis considering unit width for analysis. Index Termsâ€”Underpass skew bridge, Three-dimensional Finite element analysis, Soil-structure interaction, Haunches.