Debonding strands as an anchorage zone crack control method for pretensioned concrete bulb-tee girders

Abstract

■ Variations in girder depth, total number of strands, and debonding ratio were reviewed with the finite element analysis models. To meet bridge load demands efficiently, pretensioned concrete bulb-tee girders are heavily prestressed in most cases. Although the pretension force is transferred gradually to concrete near girder ends, tensile stresses developing in the anchorage zones can be large enough to create cracks in relatively thin girder webs. Deeper girders with larger prestressing forces tend to have more, longer, or wider cracks. When end zones are not encased in concrete diaphragms, cracks may create concerns for corrosion. Tadros et al. recommended repairing cracks between 0.012 and 0.050 in. (0.30 and 1.27 mm) in width and rejecting girders with cracks larger than 0.050 in. in width.