Live Load Testing of NEXT-D Bridges to Determine Distribution Factors for Moment

Abstract

Live load tests were conducted on an in-service bridge containing decked Northeast Extreme Tee (NEXT-D) girders. The purpose of the tests was to evaluate transverse load distribution and to determine which (if any) of the AASHTO LRFD standard bridge sections should be considered when calculating moment distribution factors (DFM). The NEXT-D girders in the test bridge span 12.2 m (40 ft) and utilize ultrahigh performance concrete as the girder shear key fill. The live load tests consisted of crawling (<5 mph) loaded dump trucks at several critical transverse locations across the bridge while simultaneously measuring bending strain in the girders. From this data, experimental interior and exterior girder DFMs were calculated for both one and two lane loads. Based on comparison with the experimental DFMs, it is recommended that the AASHTO LRFD type-k standard bridge section be used when calculating design moment distribution factors for NEXT-D girders.