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 Terms—Underpass skew bridge, Three-dimensional Finite element analysis, Soil-structure interaction, Haunches.