Effect of Skewness on Deck Girder Bridges

Abstract

Changing social needs and increasing traffic have led to the demand for increased infrastructure. Due to limitation of the space and to maintain highway as straight as possible for road users, the demand for skew bridges have naturally increased. When the girders of a bridge are not perpendicular to the substructure, it is known as a skew bridge. When the skew angles are more than or equal to 20 degrees, it will have significant impacts on the behaviour of the deck girder bridges. Most deck girder bridges are built solely with a single type of beam like T-beam, Y-beam, U-beam and etc. Combined Y- and U- Beams are not particularly a popular choice among the designers for bridges with various span lengths. This paper presents an investigation on the effect of live load on support reactions and on girder moments of combined Y-beam and U-beam skew bridge decks. Grillage analysis is carried out using commercially available general purpose finite element software LUSAS V12.3 to investigate the behaviour of deck girder skew bridges. Several parametric studies are carried out to examine the sensitivity of the predicted bending moment and support reactions in the various input parameters including variations in the span length and skew angles. It is found that the support reactions at the obtuse corners are always bigger than that at the acute corners except for 0˚ skew where obtuse and acute corners are absent. When a stiffer beam is placed at the line of motion, it reduces the impact on the girders at the edge.