Bridge load posting signs that provide maximum weights for different vehicles are designed to keep motorists safe. Placing more weight on a bridge than it was designed for imposes stress on the structure and shortens the service life of the bridge. However, load postings also require more state department of transportation maintenance and inspection, as well as cause increased travel time and distance for freight trucks subjected to weight restrictions. Currently, AASHTO provides guidance on load rates for bridges using three load-rating methods that help predict the performance of the bridge by using generalized equations and expressions.
In a study for a paper in the Journal of Bridge Engineering, researchers Matthew Stieglitz, Tevfik Terzioglu, Mary Beth D. Hueste, Stefan Hurlebaus, John B. Mander, and Stephanie G. Paal investigated whether the load rating of continuous steel girder bridges could be improved. Their paper “Field Testing and Refined Load Rating of a Load-Posted Continuous Steel Girder Bridge” used a load-posted three-span continuous steel bridge in Texas. The authors applied three methodologies: the first was to account for partial composite action; the second examined the live load distribution of the girders; and the last developed refined live load distribution factors. Learn more about how this research could help state DOTs manage bridge inventory and provide economic benefits for the trucking industry at https://doi.org/10.1061/(ASCE)BE.1943-5592.0001927. The abstract is below.
Load-posted bridges have potential effects on traffic, commerce, and emergency egress due to detours in routes between origins and destinations. Posted bridges can also be problematic for state departments of transportation from a management standpoint because they may call for more frequent maintenance, monitoring, and inspection. For these reasons, it is beneficial for states to minimize the number of load-posted bridges. This study investigates a continuous steel plate girder bridge superstructure and proposes a methodology for exploring the refined load rating of this bridge type in a safe manner through refined modeling and load testing. Load test results were used to examine live load distribution factors, and finite-element models were developed to refine load ratings. It was determined that the refined load-rating factors for the bridge are significantly higher than the currently posted limits, and therefore, the posting could be removed. The methodology presented in this paper can potentially be used to increase the load-rating factors for similar continuous steel girder bridges.
Read the paper in full in the ASCE Library at https://doi.org/10.1061/(ASCE)BE.1943-5592.0001927.