Monitoring of Damage in Prestressing Tendons Using Ultrasonic Guided Waves

Abstract

One of the most common constructions nowadays is Pre-stressed Concrete structures. But due to deterioration of tendons caused by corrosion in concrete/grout, catastrophic collapses of Prestressed concrete constructions have been observed. Thus, a rigorous inspection of the embedded tendons in PSC for corrosion related damages on a regular basis is imperative. In the present work, high frequency ultrasonic guided waves have been utilized to develop a damage detection methodology for tendons embedded in concrete corrosion of simulated notch and debond defects. Conventional techniques of pulse transmission and pulse echo techniques are for testing. The time of flight in P/E and signal attenuation in both P/E and P/T have been observed to locate and quantify damages accurately. The method is then successfully applied to reinforced concrete beam specimens with embedded tendons undergoing accelerated chloride corrosion. Ultrasonic guided waves have been identified as a potentially effective technique for monitoring tendon corrosion in concrete. Suitable surface and core seeking ultrasonic guided wave modes have been identified which are sensitive to delamination and pitting effects of corrosion respectively. These modes are used to ultrasonically monitor reinforced concrete beams undergoing accelerated impressed current corrosion in chloride environment. The simulated and actual corrosion results are compared to show suitability of simulated techniques. The ultrasonic signals effectively relate to the state of pre-stressing tendon undergoing actual corrosion. Tendon in concrete results in pitting of tendons and debonding from surrounding grout. Hence, it is simulated in the form of notches (represents area loss) and delamination (represents debonding). Hence, it is concluded that ultrasonic guided waves can be utilized for onsite inspection of embedded tendons for any breaks/cracks in tendons and corrosion related damages. Certain practical issues have to be looked into before it can be successfully developed into a fully fledged monitoring system.