Effects of Existing Shear Damage on Externally Posttensioned Repair of Bent Caps

Abstract

External posttensioning can be considered an effective strengthening method for bridge members, which are deteriorating due to extreme loading conditions and progressive structural aging. The effects of existing shear cracks in bent caps strengthened by external posttensioning were experimentally investigated using model specimens. Initial investigation revealed that the shear capacity of a bent cap is not enhanced by external posttensioning only, when shear cracks exist. Moreover, it was found that the repair of existing cracks using epoxy injection substantially increases the shear capacity of the bent cap. The Tenthill Creek Bridge in South East Queensland, Australia provides a case study where the bent caps have been strengthened by external posttensioning. The model tests of the bridge bent caps confirmed the initial findings on the effects of existing shear cracks on the shear capacity. The experimental results emphasize the need for appropriate repair of existing shear cracks prior to strengthening by external posttensioning to enhance the shear capacity of bent caps.