Influence of Skew Angle on Continuous bridges

Simply supported structures are used efficiently for bridge up to a certain span limit, beyond which the use of continuous structure becomes more economical. Continuous composite steel-concrete bridges remain one of the most common types built. The proper design of this structure requires accurate prediction of their structural response to truck loads. Many of cods provide guide lines for design of simply supported composite bridges, while dose not account for the effect of skew and continuity, Therefore is extremely conservative since both skew and continuity influence the longitudinal moments and shear in the girders. In this parametric studies effect of skew angle as well as other design parameters on more than 72 prototype continuous composite cases with six I-section girders and span ratio (1, 1.55, and 1.82) are analyzed using the finite-element method. The data generated from parametric study is used to deduce expressions for both support moment and shear distribution factors for AASHTO track loading and usual load of Iran-cods. Results from finite-element analyses shows that the support moment in internal and external girders decreases significantly with increase in the skew angle, this decrease is about 8 percent when skews are less than 20°, with increase in skew angle up to 45° the support moment decreases about 30 percent. The shear forces in pier support increase at the exterior girder and decreases at the interior girders with increasing skew. Results from comparing of two mentioned loads show that support moment in the case of AAHTO loading more decreases than Iran’s usual loading.