Long-Term Deformations and Prestress Losses in Precast, Prestressed Bridge Girders

Abstract

Self-consolidating concrete (SCC) is widely becoming used to construct precast, prestressed bridge girders. In order to determine the acceptance of SCC for 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. The objective of this report is to research the time-dependent deformation for the bridge girders included in this investigation. Twenty-eight bulb tee girders were instrumented with strain gauges for the replacement bridge constructed on State Route 22 over Hillabee Creek in Tallapoosa County, Alabama. Half of the spans girders were constructed with SCC while the remaining half were constructed with conventional vibrated concrete (VC). Fresh concrete properties were determined while the girders were located at the plant, while internal strain and camber measurements were taken from the time of prestress transfer until the bridge was in service for one year. These internal strains were used to determine the prestress losses at various stages of the construction process. The measured prestress losses for the girers were compared with predicted values determined using the provisions of the AASHTO LRFD 2012 Bridge Design Specification. Time-dependent deformation comparisons were also made between SCC and VC girders. The AASHTO 2012 prediction method over predicted the prestress losses for both types of concrete. There seemed to be no differences in the time-dependent deformations between the SCC and VC girders in this investigation