Enhanced camber and deflection estimation for AASHTO prestressed concrete girders

[摘要] In precast, prestressed concrete bridge girders, a largenumber of prestressing strands are placed in the bottom flange to increase the structural capacity of thegirder. The concentration of the prestressing strands belowthe neutral axis of the girder cross section causes an upward deflection, technically termed camber. During girderfabrication, prestressing strands are tensioned between twoabutments, and then concrete is placed. When the concreteachieves the required compressive strength, the strandsare cut and the force from the strands is transferred to thehardened concrete. This transfer of prestressing force resultsin a bending moment, which creates the upward deflection.1Accurate prediction of camber is essential, especially duringfabrication of cast-in-place concrete bridge decks. If thecamber at erection is less than the design value, the deckthickness must be increased, and this adds extra weight thatwas not accounted for in the design. If the camber is greaterthan the predicted value, the top flange of the girder may interfere with the deck reinforcement. In both cases, the deckprofile may have to be adjusted. This additional task can leadto changes in the construction plans, which will delay theproject and increase costs.

[学科分类] 建筑学