Load Rating of Concrete Slab-span Bridges

Abstract

Three slab-span bridges crossing Shingle Creek in Brooklyn Center, MN have poor AASHTO load rating factors for certain truck configurations. Characterization of load distribution is useful for determining the load rating of bridges, but results in the literature have shown that the AASHTO code results in conservative load rating factors. The focus of this study was to determine if the load rating of the three concrete slab-span bridges was conservative and could be improved using results from live load testing and finite element analysis. Field testing utilized a suite of instrumentation that included displacement transducers, strain gauges, accelerometers, and tiltmeters. A three- dimensional solid-element finite element model was used to determine an expected range of behaviors and corroborate the field data regarding how load distributed when placed near and away from a barrier. Additionally, a method for developing a simple plate model of slab span bridges was developed considering in-situ material properties and effects of secondary elements such as barriers. Results indicated that the AASHTO load rating is conservative, and an improved rating factor could be obtained considering the field test data and computational modeling results.