Date of Award


Document Type


Degree Name

Master of Science (MS)


Civil Engineering

Committee Member

Thomas E. Cousins, Committee Chair

Committee Member

Brandon E. Ross

Committee Member

Weichiang Pang


For short to medium span bridges experiencing lower average daily traffic (ADT), the South Carolina Department of Transportation (SCDOT) currently utilizes both hollow core and solid slab precast concrete span bridge sections. The intended advantages of these bridge sections were that they could be built according to an accelerated bridge construction (ABC) schedule and have increased durability. Increasing a bridge's durability has economic advantages since they require less maintenance and have a greater lifespan. Both the precast hollow core and solid slab spans have not met the SCDOT's durability requirements. Deterioration of the grout key between adjacent precast members has led to reflective cracking in both the bridge deck and bridge wearing surface. These cracks allow water and other corrosive materials to infiltrate the precast beam sections, and lead to the corrosion of the prestressing strands and reinforcement. Corrosion of prestressing leads to bridge repairs as well as a diminished life-span, both costly to the SCDOT. Reflective cracking at the shear key also leads to a decreased ability for a bridge to share load among its adjacent members. Both hollow core and solid slab sections are designed to distribute load transversely across the bridge and longitudinally to the girder bearings. Individual girders resist only a portion of the loads on a bridge. If the shear key is degraded and its ability to share load lessened, a possible overload and catastrophic failure of a bridge member could occur. These durability issues have proved to be problematic and have concerned the SCDOT. The SCDOT and Clemson University teamed up to conduct research in order to identify, modify, or develop a bridge type that was both more durable and could meet the schedule of ABC. The SCDOT and Clemson University settled on the northeast extreme tee (NEXT) beam, developed by the bridge technical committee of PCI Northeast. The NEXT beam section is an advantageous bridge section for many reasons, including its geometric diversity, ability to meet an ABC schedule, utility accommodations, full deck option, and a wider shear key allowing for an easier concrete pour or grouting. The NEXT beam cross section does not fall into an AASHTO LRFD category for simplified moment live load distribution factors. This project seeks to calculate live load distribution factors via live load test, and determine what, if any, category the NEXT section can fall under for simplified moment live load distribution factors. A future research project will assess the durability of the UHPC shear keys for both the NEXT D and solid slab span by monitoring the ability for girder sections to share load transversely over a period of two years. Results of this research will be given to the South Carolina Department of Transportation (SCDOT) so that they may be informed on how NEXT Beam transverse moment distribution behavior. Results on UHPC shear key performance and durability will also be given to the SCDOT.



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