Impact of Specialized Hauling Vehicles and Emergency Vehicles on Bridge Load Rating

Abstract

The Federal Highway Administration (FHWA) mandated states to adopt specialized hauling vehicles (SHVs) and emergency vehicles (EVs) in 2013 and 2016, respectively, in the load rating of bridges. Both the AASHTO single-unit trucks (SUs) and EVs are specially configured so that they may result in high load effects and can adversely affect bridge load rating factors. This paper investigates the impacts of rating these vehicles on the states’ bridge load ratings. An extensive literature review of the states’ load rating policies is performed. To determine whether any state can possibly be exempted from the new load ratings for SUs and EVs for Interstate highway bridges, the load effects of various state legal vehicles are analyzed and compared with those of SUs and EVs. The results of the study indicate the inevitability of executing the new load rating analysis for SUs and EVs for the vast majority of states. Weigh-in-motion data are processed to screen the potential EV traffic fleeting on the highway, and the calibrated live load factors are proposed for EVs accordingly. The load effects are found to be smaller than those FHWA originally assigned, improving the rating factors. Lastly, this paper proposes a screening tool to help state agencies to convert the known rating factors to the rating factors of SUs and EVs so that the load rating work can be prioritized for the bridges that are vulnerable to SUs and EVs.

Reliability-Based Assessment of Concrete Decks Designed Using Approximate Method at the Strength I Limit State

“…As raised by NCHRP Project 12-76 ( 5 ) and emphasized again by the Transportation Research Board Consensus Study Report ( 6 ), the single and tandem axle load can be much heavier than the design load. For example, the traversing of the emergency vehicles, which are exempted from the Federal Bridge Formula B, contributes to both heavy single axles and heavy tandem axle ( 7 ). Moreover, with the growing popularity of specialized hauling vehicles tridem axles are becoming more common, whose load effects have not been evaluated thoroughly ( 8 ).…”