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The need to strengthen the existing reinforced concrete (RC) elements is becoming increasingly crucial for modern cities as they strive to develop resilient and sustainable structures and infrastructures. In recent years, various solutions have been proposed to limit the undesirable effects of corrosion in RC elements. While C-FRP has shown promise in corrosion-prone environments, its use in structural applications is limited by cost, bonding, and anchorage challenges with concrete. To address these, the present research investigates the structural performance of RC beams reinforced with C-FRP bars under static loading using Structural Health Monitoring (SHM) with an Electro-Mechanical Impedance (EMI) system employing Lead Zirconate Titanate (PZT) piezoelectric transducers which are applied to detect damage development and enhance the protection of RC elements and overall, RC structures. This study underscores the potential of C-FRP bars for durable tensile reinforcement in RC structures, particularly in hybrid designs that leverage steel for compression strength. The study focuses on critical factors such as stiffness, maximum load capacity, deflection at each loading stage, and the development of crack widths, all analyzed through voltage responses recorded by the PZT sensors. Particular emphasis is placed on the bond conditions and anchorage lengths of the tensile C-FRP bars, exploring how local confinement conditions along the anchorage length influence the overall behavior of the beams. [ABSTRACT FROM AUTHOR]

Climate change induces extreme effects with lower-than-designed restoration periods, imposing the necessity of strengthening the structural integrity of existing and mainly older RC structures, which are often demonstrated to be under-reinforced in terms of the shear capacity, mainly due to outdated and old design codes/standards. Thus, finding cost-effective and feasible methods to strengthen RC elements is becoming increasingly important. Thin RC layers for jacketing represent a modern advancement in repairing and retrofitting RC members. In this context, U-shaped mortar jackets were employed to strengthen three shear-critical beams. In addition, a critical aspect in the success of any jacketing method is the degree of bonding and interaction between the original member and the new jacket. Additionally, the performance of these U-shaped jackets was assessed using an Electro-Mechanical-Impedance-based (EMI-based) method using a Piezoelectric-Transducer-enabled (PZT-enabled) technique. The integration of advanced monitoring technologies in retrofitting applications offers valuable insights into the performance and longevity of the retrofit system. Therefore, this study aims to experimentally investigate the cohesion between construction materials and assess the effectiveness of U-shaped jackets. Through the proposed Structural Health Monitoring (SHM) technique, any degradation at the interface or slippage of the retrofitting jacket can be promptly detected, restraining further damage development and potential failure of the structure. [ABSTRACT FROM AUTHOR]

Due to insufficient transverse reinforcement, the retrofitting of beam–column joints (BCJs) in existing reinforced concrete (RC) frame structures is commonly required to alter their brittle behavior. The construction industry has extensively embraced carbon-fiber-reinforced polymers (C-FRPs) as near-surface-mounted (NSM) reinforcement. Monitoring the performance of C-FRP retrofitting is crucial due to the wide range of factors influencing its effectiveness. A novel methodology has been implemented to assess the efficacy of the C-FRP retrofitting method in this study. This approach was validated through experimental investigation of full-scale BCJs, which were retrofitted with C-FRP ropes and subjected to cyclic loading. Furthermore, piezoelectric lead zirconate titanate (PZT) patches were placed on the NSM C-FRP ropes, and the electro-mechanical impedance (EMI) method was employed to monitor the retrofitting technique's performance. A combination of the commonly used statistical damage index root mean squared deviation (RMSD) and a hierarchical clustering-based approach (HCA) was used to assess the performance of the C-FRP retrofitting technique. The experimental investigation results strongly indicate the proposed approach's positive impact on the reliable assessment of C-FRP retrofitting performance. Thus, the proposed approach enhances the safety and resilience of retrofitted BCJs in RC structures. [ABSTRACT FROM AUTHOR]

Real-time structural health monitoring (SHM) and accurate diagnosis of imminent damage are critical to ensure the structural safety of conventional reinforced concrete (RC) and fiber-reinforced concrete (FRC) structures. Implementations of a piezoelectric lead zirconate titanate (PZT) sensor network in the critical areas of structural members can identify the damage level. This study uses a recently developed PZT-enabled Electro-Mechanical Impedance (EMI)-based, real-time, wireless, and portable SHM and damage detection system in prismatic specimens subjected to flexural repeated loading plain concrete (PC) and FRC. Furthermore, this research examined the efficacy of the proposed SHM methodology for FRC cracking identification of the specimens at various loading levels with different sensor layouts. Additionally, damage quantification using values of statistical damage indices is included. For this reason, the well-known conventional static metric of the Root Mean Square Deviation (RMSD) and the Mean Absolute Percentage Deviation (MAPD) were used and compared. This paper addresses a reliable monitoring experimental methodology in FRC to diagnose damage and predict the forthcoming flexural failure at early damage stages, such as at the onset of cracking. Test results indicated that damage assessment is successfully achieved using RMSD and MAPD indices of a strategically placed network of PZT sensors. Furthermore, the Upper Control Limit (UCL) index was adopted as a threshold for further sifting the scalar damage indices. Additionally, the proposed PZT-enable SHM method for prompt damage level is first established, providing the relationship between the voltage frequency response of the 32 PZT sensors and the crack propagation of the FRC prisms due to the step-by-step increased imposed load. In conclusion, damage diagnosis through continuous monitoring of PZTs responses of FRC due to flexural loading is a quantitative, reliable, and promising application. [ABSTRACT FROM AUTHOR]

Reinforced Concrete (RC) members in existing RC structures are susceptible to shear-critical due to their under-reinforced design. Thus, implementing a retrofitting technique is essential to eliminate the casualties that could arise from sudden and catastrophic collapses due to these members' brittleness. Among other proposed techniques, using Carbon-Fiber Reinforced Polymers (C-FRP) ropes to increase the shear strength of RC structural elements has proved to be a promising reinforcement application. Moreover, an Electro-Mechanical Impedance (EMI-based) method using Lead Zirconate Titanate (PZT-enabled) was employed to assess the efficiency of the strengthening scheme. Initially, the proposed technique was applied to C-FRP rope under the subjection of pullout testing. Thus, a correlation of the rope's tensile strength with the EMI responses of the PZT patch was achieved using the Root Mean Square Deviation (RMSD) metric index. Thereafter, the method was implemented to the experimentally acquired data of C-FRP ropes, used as shear reinforcement in a rectangular deep beam. The ropes were installed using the Embedded Through Section (ETS) scheme. Furthermore, an approach to evaluate the residual shear-bearing capacity based on the EMI responses acquired by being embedded in and bonded to the ropes' PZTs was attempted, demonstrating promising results and good precision compared to the analytical prediction of the C-FRP ropes' shear resistance contribution. [ABSTRACT FROM AUTHOR]