Abstract
Prestressing bars or prestressing wires are employed as transverse prestressing tendons in cross-beams and concrete slabs of prestressed concrete (PC) bridges. The ducts for inserted tendons are normally grouted. Inadequately grouting, however, may lead to tendon corrosion and breakage. The breakage of tendons sometimes results in the projection of a torn portion from the bridge, causing a serious public safety hazard. The impact Elastic Wave Methods technique was employed to study the effect of voids in post-tensioning grouted ducts of PC bridges in service. Two indices were introduced to evaluate inadequately grouted ducts for transverse prestressing. One is the velocity of the elastic wave propagated in the tendon, and the other is the presence of high frequency components observed at the beginning portion of the received wave. After confirming the applicability of the technique for detecting inadequately grouted ducts for transverse prestressing, it was demonstrated that the technique can also be applied for inspecting restored ducts after re-grouting. Further, it may be possible to improve the reliability of the diagnosis by taking into account the rise time of the received waves.
