United States Department of Transportation
i
Truck Platooning Effects on Girder Bridges: Phase II-Service
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2023-08-11
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[PDF-24.86 MB]
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Edition:Final Report July 2021-May 2023
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Abstract:Truck platooning—wirelessly linking two or more trucks to travel in a closely spaced convoy—is federally promoted to save fuel, improve the environment, and improve traffic operations. Platooning places trucks much closer than current design codes anticipate. While this strategy can provide higher fuel efficiency, it also can potentially overload structures. Previous reliability based studies (Steelman et al., 2021; Yang et al., 2021) have focused on the Strength I limit state and have shown that trucks can operate at weights exceeding standard legal load limits even with short headways at operating-level reliability. However, service limit states in the AASHTO LRFD Bridge Design Specifications (2020) were not originally calibrated to produce uniform safety through reliability theory. Currently, no target implicit reliability index (βImplicit) nor reliability-based evaluation guidance for the service limit states is stated in the AASHTO Manual for Bridge Evaluation (2018). In addition, a reliability-based service limit state evaluation protocol for bridges subjected to platoons does not currently exist. A parametric study considered different girder spacings, span lengths, span numbers, structure types, truck configurations, truck numbers, and adjacent-lane loading scenarios. Using Monte Carlo Simulation (MCS), target βImplicit values were identified based on current design loads to calibrate heavy-load limits for the service limit state (e.g., permit vehicles and platoons). LRFR live load factors were developed for service over a range of coefficients of variation (CoVs) and were presented in association with a potential new permit load, i.e., a platoon permit. The framework for explicitly aggregating live load uncertainties based on truck weight, dynamic amplification, and girder distribution factors was developed and proposed. Four representative steel and prestressed concrete girder bridges from the Nebraska inventory were load rated for strength and service. The study also preliminarily evaluated the fatigue performance of welded cross-frame connections to girder flanges and shear studs for the steel bridges and determined cracking probabilities (βCracking) for prestressed concrete bridges. As an illustration of possible operational strategies, headway guidance information and a summary of guidelines were developed for platoon loads, including varying truck weights.
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