Effects of production practices on camber of prestressed concrete bridge girders

摘要

>This paper presents the results of research to investigate factors related to prestressed concrete girder production that could affect the camber and to recommend camber prediction methods. At prestress transfer, the actual concrete compressive strength was found to be an average of 25% higher than the specified transfer strength, thus affecting the camber predictions. At 28 days, the actual compressive strength was found to be an average of 45% higher than the specified 28-day strength. Camber behavior was found to vary among different girder types and curing methods. The deformation of internal void forms in box beams and cored-slab girders due to the hydrostatic pressure of the fresh concrete during casting was found to significantly affect camber. In addition, strand debonding and transfer length were found to be non-negligible when predicting camber for some girders.A refined camber prediction method was developed that uses creep coefficients and prestress losses based on the 2010 AASHTO LRFD Bridge Design Specifications. An approximate method based on PCI Design Handbook: Precast and Prestressed Concrete camber multipliers was also proposed. The measured cambers of 382 prestressed concrete bridge girders were compared with the predicted values. The proposed methods were both found to provide reasonable estimates of camber, though the refined method was more accurate for the majority of girders.