Date of Award
Master of Science (MS)
Thomas E. Cousins, Committee Chair
Brandon E. Ross
Several of the adjacent precast concrete bridge girders (APCBG) that the South Carolina Department of Transportation (SCDOT) currently use experience shear key cracking within their intended design lives. This leads to a decrease in the transverse load sharing capabilities of these sections. Shear key cracking also leads to reflective cracks developing on the bridge deck, which allows water and other corrosive agents access to the girder reinforcement. APCBGs are often used by SCDOT for short to medium span, accelerated bridge construction (ABC) applications. Thus, SCDOT teamed up with Clemson University (CU) to seek an APCBG section that does not lead to the deficiencies the solid core, voided slab, and other APCBG sections currently used by SCODT experience. Northeast Extreme Tee (NEXT-D) girders were considered as a viable replacement to the currently used APCBG sections, and were implemented on the Hanging Rock Creek Bridge (HRB). The NEXT-D girder has proven to be successful in other states since it was first utilized in Maine in 2007. Its, wide, full depth shear key provides a robust transverse connection between the girders and its geometry makes inspection of the girder easier for state DOT officials. Additionally, utilities may be attached to the girder without sacrificing vertical clearance and it has been employed in ABC applications. The SCDOT/CU research team studied the NEXT-D girder span on the HRB to evaluate its performance. Live load tests were conducted on the HRB NEXT-D span to evaluate the transverse load distribution and shear key durability of the NEXT-D girders. Additionally a live load test was conducted on the solid span to evaluate the shear key durability of the solid core girders. Another purpose of the tests was to determine which (if any) of the AASHTO LRFD standard bridge sections should be considered when calculating moment distribution factors (DFM). The NEXT-D and solid core girders in the test bridge have a 40 foot span length and utilize ultra-high performance concrete as the girder shear key fill. The live load tests consisted of crawling (< 5 mph) loaded dump trucks at several transverse locations across the tested bridge spans while simultaneously measuring bending strain, shear strain, and relative horizontal displacements in the girders. From this data, experimental interior and exterior girder moment distribution factors (DFM) were calculated for both one and two lanes loaded and compared to code-calculated DFMs, shear key deterioration (or lake thereof) was evaluated, and shear strains due to shear forces and torsion were evaluated for calculating experimental shear distribution factors. The live load test results indicate that the solid core girder shear keys crack sooner than the NEXT-D girder shear keys under similar load conditions and that AASHTO LRFD section typology “k” be used when code-calculating moment distribution factors for NEXT-D girders. Finally, the live load test results suggest that strain transducer rosettes be used on either side of each girder web to calculate experimental shear distribution factors.
Hess, Samuel Edward, "Live Load Distribution Factors and UHPC Shear Key Performance of SCDOT NEXT-D Beam" (2018). All Theses. 2987.