Time-Dependent Deformations in Precast, Prestressed Bridge Girders
Type of Degreethesis
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Precast, prestressed girders are used across the state of Alabama for bridge construction. There has been a desire to allow self-consolidating concrete to be used to manufacture these bridge girders. The time-dependent deformation response of bridge girders that contain self-consolidating concrete is important information that must be gathered before the use of self-consolidating concrete in bridge girders can be widely used in the state of Alabama. Twenty-eight bulb-tee girders were measured for internal strain and camber. Fourteen of the girders were composed of conventionally vibrated concrete while the remaining girders were composed of self-consolidating concrete. Predicted internal strains and cambers for these girders were found through the use of a time-step process. These predictions were formed based on creep and shrinkage methods allowed by the AASHTO LRFD 2010 Bridge Design Specification. These predictions were compared to the measured results in order to determine which prediction methods were the most accurate. The comparison of time-dependent responses showed that girders constructed with self-consolidating concrete exhibit similar performance characteristics to those of girders constructed with conventionally vibrated concrete. The time-dependent deformation response can be accurately predicted if the concrete strength and stiffness is known at the time of prestress transfer. Predictions that use specified concrete strength and stiffness values that do not accurately represent actual strength and stiffness values will yield largely inaccurate predictions of time-dependent deformation.