Abstract: Taking a prestressed concrete prefabricated simply supported girder bridge asengineering background, the influence of oblique angle, span, bridge width and transverse torsional stiffness on the fundamental frequency of the bridge is analyzed by numerical method. The results show that as the skew angle becomes larger, the first three orders of the vertical natural vibration frequencies increase. With the increase of the span, the whole vertical stiffness becomes lower, the fundamental frequency reduce obviously, but the rate to deduction decreased gradually. The fundamental frequency affected by the mechanical characteristic of coupling of bending and torsion increases with the increase of torsional stiffness. Based on the influence of key factors above on the base frequency of the skew beam bridge, an improved formula, taking the torsional stiffness and the skew angle into account, for estimating the base frequency of the concrete simply supported skew beam bridge is therefore proposed. The precision and the applicability of the formula are verified by all measured data of several real bridges.

Key words: simple supported beam bridge, skew angle, fundamental frequency, revised formula, vehicle-bridge coupled vibration