Inference of bond slip in prestressed tendons in concrete bridge girders

Prestressed concrete (PC) bridge girders have extra flexural strength due to embedded prestressing tendons. The level of strength depends on the integrity of the concrete-tendon bond in pretensioned PC structures, and this bond can be degraded in the presence of an adequately large mechanical force or over time because of accumulated damage. Bond degradation is characterized by the bond slip of the tendon from the host concrete, and in regards to PC structures, bond slip has only been measured from a global perspective. In this paper, a novel method was developed to measure for the first time the local strain of a prestressing tendon during bond slip. Fiber Bragg grating-based strain sensors were installed directly onto prestressing tendons within a PC girder to provide a local perspective of bond slip as the girder was loaded to failure. Measurement of the local strains in selected tendons, from the beginning of bond slip to the complete loss of the concrete-tendon bond, and the failure of the girder was enabled by the method. Copyright (c) 2014 John Wiley & Sons, Ltd.