Live-Load Factor and Load Combination for Bridge Systems Conveying Extremely Heavy Mining Trucks

The highly predictable and unusually heavy loading on bridges carrying mine haul trucks should be accompanied by advancement in the current bridge design code provisions. Mine haul trucks are optimally designed to match the capacity of large loading shovels, which provide a set number of consistent volumes of ore at efficient loading frequencies. In this research, reliability-based design procedures were implemented to calibrate live-load factors for bridge systems conveying extremely heavy mining trucks (gross operating weight of approximately 700 t). Field measurements of the gross vehicle weight of trucks were used in the calibration process. Analysis results suggest a live-load factor of 1.33 for trucks moving on short-span composite steel girders or NU precast girder bridge systems. Analysis results also recommend the adjustment of the load combination in the design code to treat the barrier dead load as a separate random variable with a load factor of 1.36. Simplified live-load and barrier-load distribution factors for interior and exterior girders in bridges transporting heavy trucks were developed based on a regression analysis. The developed distribution factors are recommended to be used in alignment with the calibrated live-load and barrier-load factors. Modifications to the live-load provisions in the current design code are recommended based on the conclusions drawn from this study.