Field Study of Live Load Distribution Factors and Dynamic Load Allowance on Reinforced Concrete T-Beam Bridges

摘要

This study focuses on the evaluation of live load distribution and dynamic load allowance factors for reinforced concrete T-beam bridges subject to heavy military-vehicle loading. Field displacement measurements on actual bridges were incorporated as part of the evaluation procedure. The vehicle under consideration in this study was a U.S. Army Palletized Loading System (PLS) military vehicle. Results from this evaluation were compared to those obtained from a civilian dump truck owned by the Virginia Department of Transportation (vDOT). The comparative evaluation also considered the design guidelines presented in the American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Highways Bridges and the AASHTO Load Resistance Factor Design (LRFD) Bridge Design Specifications. Two typical cast-in-place reinforced concrete T-beam bridges were selected for field testing with the vehicle under various transverse position scenarios. It was concluded that there was not an appreciable difference in the load distribution factors obtained from the PLS truck and the civilian dump truck. In all instances, the load distribution factor obtained for the PLS truck was smaller than the value specified by the AASHTO Standard Specifications. Results cornering the dynamic load allowance factor for the PLS truck were inconclusive due to the difficulty in controlling the position of the truck over the bridge deck at high speeds. The information derived from this study will contribute in the development of accurate methodologies for the determination of load-carrying capacity of bridges.