Document Type



In this study, a reliability-based calibration of live load factors for bridge design specific to the State of Michigan was conducted. Two years of high frequency WIM data from 20 representative state-wide sites were analyzed, and load effects were generated for bridge spans from 6 to 122 m (20 to 400 ft), considering simple and continuous moments and shears, as well as single lane and two lane effects. Seventy-five year statistics for maximum live load were then estimated with probabilistic projection. Bridge girders considered for the calibration included composite steel, prestressed concrete, side-by-side and spread box beams, as well as special long span structural members. In some cases, it was found that Michigan load effects are greater than those previously assumed, often requiring higher load factors than in current use. Moreover, significant variation in the required load factor was found, potentially resulting significant inconsistencies in reliability if a single load factor is used for the design of all bridge types and load effects considered.


Applied Mechanics | Structural Engineering


This is the final draft of an article published in Journal of Bridge Engineering, 21(6), (2016) © ASCE, available online at: