Reliability of long-span continuous beam bridges during girder transport

ObjectiveThis study investigates the reliability of long-span continuous beam bridge under heavy load of girder transport vehicles, ensuring safety during girder transport.MethodA long-span continuous beam bridge with the main-span of 135 m was selected as a case study. First, the load effects on key sections during girder transport were calculated by using Midas Civil software. Second, the girder transport scenario was classified as a transient design situation. The load factors at limit state were discussed and determined. Third, the statistical parameters for resistance and load effects were analyzed. JC method-based Matlab program was used to calculate reliability indexes of bearing capacity of each key section. Finally, the differences among reliability indexes were compared.ResultThe girder transport scenario belongs to transient design situation. At the limit state of bearing capacity, the recommended importance factor is taken as 1.1; the recommended partial factor for dead load is taken as 1.0; the recommended partial factor for live load is taken as 1.1. Reliability indexes for flexural capacity are relatively low in some sections; and the minimum value is 3.06 at mid-span section. In contrast, reliability indexes for shear-bearing capacity are high in all sections, ranging from 16.47 to 21.25. The importance factor has significant influences on reliability indexes. The influences of partial factors for dead and live loads depend on the magnitude of load effects at each section. The factor values proposed in this study are more reasonable than those in current specifications.ConclusionThe load of super-heavy girder transport vehicles significantly affect structural safety. Attention must be focused on the flexural capacity of critical sections during girder transport. These findings would provide a valuable reference for safety assessment of long-span bridges.