Reliability-based evaluation of load carrying capacity for a composite box girder bridge

The load carrying capacity of a composite open-top steel box girder bridge was evaluated, based on a reliability-based method, and potential differences from conventional approaches were evaluated. A practical analysis model was utilized in evaluating the Rating Factor (RF) after verification with a rigorous full finite element analysis model with solid and plate elements. The accuracy of the analysis models was validated in terms of displacements and distribution factors through static loading tests. Dynamic effects were also estimated from the dynamic loading tests. The load factors, proposed for the purpose of evaluation based on recently accumulated statistical data, were utilized in evaluating RF. The RFs were evaluated for maximum positive flexure, negative flexure, and shear regions along the bridge. The calculated RF with the load factors for evaluation purposes was higher by 35% than that with design load factors. The proposed method also produces a 29% increase in RF compared to the conventional allowable stress design approach. Consequently, the proposed reliability-based procedure would be expected to permit a more economical assessment of bridge performance to be made.