Abstract
This paper presents the results of a parametric study evaluating the effect of skew angle on the wheel load distribution in steel girder highway bridges. The finite element method was used to investigate the effect of various parameters such as the span length, girder spacing, and skew angle, on simply supported, one-span, two-lane, three-lane and four-lane steel girder bridges. A total of 270 bridge cases were analyzed and subjected to AASHTO HS20 design trucks positioned on each bridge to produce maximum bending in the interior steel girders. A combination of five typical span lengths, three girder spacing, and six skew angles were used in evaluating bending moments in skewed steel girder bridges. The finite element results were used to calculate the maximum bending moment in steel girders due to the various skew angles and compared to the reference straight bridges, and then compared to the reduction factors used in AASHTO LRFD Bridge Design Specifications. The finite element results showed the reduction in bending moment for all skewed bridges up to 30 degrees can be neglected and such bridges can be designed as straight bridges. These results are consistent with the AASHTO Standard Specifications and the LRFD procedure by not specifying any reduction factor for bridges with skew angles up to 30 degrees. For highly skewed bridges and span length less than 80 ft (24 m), the finite element results showed a reduction in moment ranging between 10% and 20% for skew angles up to 40 degrees, and between 20% and 35% for skew angle up to 50 degrees. For practical application, a conservative reduction in girder bending moment of 15% is suggested for skew angles between 30 and 40 degrees and another conservative reduction in girder bending moment of 25% for bridges with skew angles between 40 and 50 degrees. Furthermore, the AASHTO LRFD reduction factors, ranging between 15% and 5%, were more conservative when compared with the finite element results for short-span bridges with high skew angles.