Field Evaluation of Transverse Post-Tensioning and Latex Modified Concrete on Bridge Load Distribution

The Airport Road Bridge (ARB) over Rocky Creek in Greenwood, SC is one of 377 channel bridges in South Carolina currently load-posted, limiting vehicle weight and potentially restricting access to vital services. The South Carolina Department of Transportation (SCDOT) seeks a cost-effective method to strengthen these bridges and enhance their load-sharing capacity. Through live load field testing, this research seeks to use two retrofitting techniques – transverse post-tensioning (PT) and latex modified concrete (LMC) overlay – to determine whether or not channel bridges can be improved. Direct tension testing was also performed to evaluate the substrate-overlay bond of the LMC after undergoing reduced surface preparation. In addition to a field evaluation, LMC-topped girders were tested to flexural failure to determine the improvement LMC may have on flexural capacity. Field testing revealed that the use of a PT only retrofit improved load distribution on interior girders by over 24.8% compared to the initial condition of the bridge while a PT and LMC retrofit improved load distribution on interior girders by 23.3%, suggesting that the use of a PT only retrofit would have the greatest positive effect on channel bridges. Flexural testing proved that the capacity of an LMC-topped girder exceeded the nominal capacity of a similar precast girder. This margin could be further improved should a better interface bond be developed. The outcomes of this testing can be used as the basis upon which the SCDOT should reevaluate distribution factors and plan for the rehabilitation of channel girder bridges across the state.