Girder Moments in Continuous Skew Composite Bridges

Abstract

Simply supported structures are used efficiently for bridges up to a certain span limit, beyond which the use of continuous structures becomes more economical. As a result of continuity, support moments are developed and therefore span moments are significantly reduced. The design method specified by the American Association of State Highway Transportation Officials (AASHTO) does not account for the effect of skew and continuity and therefore is extremely conservative for skew continuous composite bridges since both skew and continuity influence the longitudinal moments in the girders. In the present paper, test results from three continuous composite steel-concrete bridge models are used to verify a finite-element analysis for such bridges. The finite-element analysis is then employed to conduct an extensive parametric study on more than 600 prototype continuous composite bridge cases. Several parameters are varied, such as girder spacing, angle of skew, bridge aspect ratio, spans ratio, number of lanes, number of girders, and intermediate transverse diaphragms. The data generated from the parametric study is used to deduce expressions for both span and support moment-distribution factors for AASHTO truck loading as well as for dead load. An illustrative design example is presented.