EFFECT OF SKEWNESS ON SIMPLY SUPPORTED GIRDER BRIDGES

Abstract

A very limited study has been carried out in the field of skew bridges and even that does not hold much relevance in Indian perspective due to difference in design live load standards and type of bridges being built here. Therefore it does not provide any help to designers regarding the quick estimation of design bending moments and shear forces which are of prime interest. For this purpose a parametric study of Simply Supported 2-Lane T-Beam Bridge has been performed in STAAD PRO. The parameters varied were span and skew angle. The effect of same was observed on maximum live load bending moment, maximum live load shear force and maximum live load reaction at critical locations in terms of Moment Distribution Factor (MDF), Shear Coefficients and Reaction Coefficients. Live Load "Class 70R Tracked", "Class 70R Wheeled" and "Class A" were applied as per IRC 6 guidelines. The spans used were 12 m, 15 m, 18 m and 21 m. The skew angles were taken at an interval of 10° starting from 0° up to a maximum of 40°. Bridges with skew angle more than 40° are rare. From the study it was observed that as the skew angle increases from 0° to 40° there is a consistent reduction in Moment Distribution Factor (MDF) of the outer longitudinal girder of bridge. Similar trend of reduction in MDF were observed for other spans. This suggests that skew bridges designed, ignoring the skew effect are conservative with respect to the bending moment. The effect of skew angle was also studied on the shear coefficients and reaction coefficients. The shear coefficients and reaction coefficients increases almost linearly with skew angle and span. Hence it can be concluded that proper estimation should be made in the live load shear and live load reactions when designing skew bridges. iii