Fiber Reinforced Polymer Debonding Failure Identification Using Smart Materials in Strengthened T-Shaped Reinforced Concrete Beams

Abstract

The favorable contribution of externally bonded fiber-reinforced polymer (EB-FRP) sheets to the shear strengthening of reinforced concrete (RC) beams is widely acknowledged. Nonetheless, the premature debonding of EB-FRP materials remains a limitation for widespread on-site application. Once debonding appears, it is highly likely that brittle failure will occur in the strengthened RC structural member; therefore, it is essential to be alerted of the debonding incident immediately and to intervene. This may not be always possible, particularly if the EB-FRP strengthened RC member is located in an inaccessible area for fast inspection, such as bridge piers. The ability to identify debonding immediately via remote control would contribute to the safer application of the technique by eliminating the negative outcomes of debonding. The current investigation involves the detection of EB-FRP sheet debonding using a remotely controlled electromechanical admittance (EMA)-based structural health monitoring (SHM) system that utilizes piezoelectric lead zirconate titanate (PZT) sensors. An experimental investigation on RC T-beams strengthened for shear with EB-FRP sheets has been performed. The PZT sensors are installed at various locations on the surface of the EB-FRP sheets to evaluate the SHM system’s ability to detect debonding. Additionally, strain gauges were attached on the surface of the EB-FRP sheets near the PZT sensors to monitor the deformation of the FRP and draw useful conclusions through comparison of the results to the wave-based data provided by the PZT sensors. The experimental results indicate that although EB-FRP sheets increase the shear resistance of the RC T-beams, premature failure occurs due to sheet debonding. The applied SHM system can sufficiently identify the debonding in real-time and appears to be feasible for on-site applications.

Failure Mode Prediction of Unreinforced Masonry (URM) Walls Retrofitted with Cementitious Textile Reinforced Mortar (TRM)

“…Similar to the failures of the GTRM system, 52% of the brick masonry walls strengthened with the CTRM system presented three different types of failures: rupture, grid slippage, and the debonding of the composite layer due to loss of adhesion [50][51][52][53][54]. Premature debonding failures of carbon fiber polymer materials have also been obtained in reinforced concrete structural members under shear loading [55][56][57]. The other 48% of the examined specimens failed in the masonry substrate, presenting with toe crushing and diagonal tension damages in the brick units [58][59][60][61].…”

Electro-Mechanical Impedance-Based Structural Health Monitoring of Fiber-Reinforced Concrete Specimens under Four-Point Repeated Loading

“…Real-time measurements of the EMI were performed using a custom-made device called a "Wireless impedance/Admittance Monitoring System (WiAMS)" and a network of PZT transducers. These devices have been extensively presented in various experimental programs by [20][21][22]26,27], proving their efficacy in detecting and evaluating damage severity in RC and FRC structural members. The theoretical components and additional information about the proposed SHM system can be found in [28,29].…”

“…Furthermore, the utilization of small-sized piezoelectric transducers that could be surface-bonded or embedded has gained widespread acceptance in EMI-based methods for SHM of concrete structural members due to their ability to act as both (a) a sensor, receiving a mechanical signal, and (b) an actuator, creating a mechanical vibration [18,19]. A reliable assessment methodology was successfully developed for SHM and assessing damage identification levels in RC structural members through a thorough investigation by Chalioris et al [20]. Notably, the reinforced concrete structural members were subjected to monotonic [21] or cyclic loading [22].…”

A Deep Learning Approach for Autonomous Compression Damage Identification in Fiber-Reinforced Concrete Using Piezoelectric Lead Zirconate Titanate Transducers

“…A large number of existing research studies in the broader literature have examined the effectiveness of EMI-based SHM of concrete due to several degradation causes, including the corrosion of steel bars in RC elements [ 14 , 15 , 16 , 17 ], concrete cover loss [ 18 ], the influence of the heating time [ 19 ], artificial cracks, and mass loss [ 20 , 21 ]. Furthermore, real-scale members of RC structures have been examined, such as beams [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], frames [ 31 ], and joints [ 32 , 33 ].…”