Debond Identification in GFRP Strengthened RC Beam Using Surface Guided Wave Mode Generated by Angle Beam Transducer

Debonding failure is one of the most common failure modes for Fiber Reinforced Polymer (FRP) strengthened reinforced concrete (RC) structures. Thus, the strengthened structure requires regular inspections using an efficient and field-friendly technique. This paper proposes the use of angle beam (wedge) transducers to identify the debonded zone in a glass fiber reinforced polymer (GRRP) strengthened RC beam. An experimental study is conducted to investigate the capability of wedge transducers to generate and receive the intended mode in the specimen. The inspection is carried out in longitudinal and transverse directions, both using the wedge and normal contact transducers. The normalised signal amplitude versus the sensor position plot is compared for ‘with wedge’ and ‘without wedge’ cases. It is found that the use of a wedge transducer significantly reduces the signal noise, thus improving the debond detection ability compared to the usage of normal transducers. Further, a three-dimensional finite element model is developed to understand the characteristics of wave propagation in the same beam specimen. The modal characteristics and normalised amplitude of signals captured in the numerical model are found in good agreement with the experimental results. Later an extensive parametric study is conducted by varying the sizes and location of debond in the validated model. This parametric investigation provides valuable insights into the detectability threshold and sensitivity of the wedge transducer, which can prove to be a competent candidate for rapid in-situ nondestructive evaluation of FRP-strengthened RC structures.