Live-Load Response of In-Service Bridge Constructed with Precast, Prestressed Self- Consolidating Concrete Girders

Abstract

In order to assess the viability of a bridge constructed with precast, prestressed, self-consolidating concrete (SCC) bridge girders in the state of Alabama, the Alabama Department of Transportation (ALDOT) sponsored an investigation to be performed by the Auburn University Highway Research Center. Researchers instrumented twenty-eight bulb-tee girders in a replacement bridge constructed on State Route 22 over Hillabee Creek in Tallapoosa County, Alabama. Two spans of the bridge were constructed using girders composed of SCC while two companion spans were constructed using girders composed of vibrated concrete (VC). The bridge was subjected to two live-load tests—one shortly before the bridge was opened to traffic and one after a year of bridge service. A finite-element model (FEM) of the bridge was also created using CSiBridge. Bridge test results and FEM predictions were analyzed in order to evaluate the acceptability and predictability of in-place SCC girder performance when subjected to design-level service loads. In addition, the accuracy of superstructure analysis techniques—including AASHTO LRFD distribution factors as well as refined analysis (FEM)—were evaluated using the measured flexural response of the prestressed concrete bridge girders subjected to truck loads. Furthermore, adjusted FEMs were used to assess the effects of cast-in-place traffic barriers and intermediate diaphragm alignment on the distribution of service-level truck loads to individual bridge girders. Based on experimental observations, it was concluded that the service-level live-load behavior of SCC girders is acceptably similar to that of VC girders. The bridge response to service loads experienced no significant deterioration after one year of service conditions. AASHTO LRFD Bridge Design Specifications (2012) methods for determining load distribution to girders within a span were determined to be generally accurate, but overly conservative in some instances and slightly unconservative in others. The inclusion of traffic barriers in analysis tended to make a significant difference in the behavior of exterior bridge girders. Intermediate webwall orientation was found to have only a small effect on transverse load distribution.