PSI - Issue 64

Nikhil Holsamudrkar et al. / Procedia Structural Integrity 64 (2024) 815–821 Holsamudrkar Nikhil et al./ Structural Integrity Procedia 00 (2019) 000 – 000

816

2

RA Risetime-Amplitude * Corresponding author. Tel.: +91-22-25764343 ; fax: +91-22-25767302. E-mail address: nikhil.nnh@gmail.com 1. Introduction

Fiber-reinforced cementitious matrices (FRCM) consist of cementitious binders reinforced with various types of fabric mesh such as glass, carbon, or PBO. Their widespread application in the strengthening of structures, ranging from bridges to buildings, underscores their advantage over other materials, such as fiber-reinforced polymers (FRP). FRCM has many advantages over FRP, such as better substrate debonding, moisture breathability, and cost effectiveness. Various studies in the domain of FRCM have proven its effectiveness for flexural strengthening (D’Ambrisi & Focacci, 2011; Giese et al., 2021; Ombres, 2011), column jacketing (Ombres, 2014; Tsesarsky et al., 2013), and shear strengthening (Al-Salloum et al., 2012; Tetta et al., 2016). Few researchers have developed models to predict the theoretical capacity of FRCM in tension and bond (Holsamudrkar et al., 2023a). Some of the methods to improve the performance of FRCM strengthening systems include the use of pre-impregnation (Holsamudrkar et al., 2024) or the use of mechanical anchorages (Aljazaeri et al., 2019; Holsamudrkar et al., 2023b). While these strategies enhance the safety factor, ensuring the structural integrity and long-term durability of FRCM-strengthened elements requires reliable health monitoring techniques. Acoustic emission (AE) monitoring emerges as a pivotal method for real-time structural health assessment due to its capability to detect and locate underlying damage mechanisms such as cracking, fiber debonding, and matrix deterioration. Unlike conventional monitoring approaches, AE provides continuous, non-invasive, and sensitive detection of structural changes, offering early warning signals for maintenance interventions. FRCM-strengthened RC component is a complex composite system comprised of concrete/masonry substrate, steel as primary reinforcement, FRCM mesh as secondary reinforcement, and cementitious matrix as a load-transferring matrix. Also, the present study utilizes on-site methodology as proposed by Holsamudrkar et al., 2024. In this method, the pre-impregnation of fabric is done with a polymer matrix to improve the fiber-fiber bond. This adds a polymer matrix as another component to the composite system. For such a complex composite system, interpreting parameters such as event rate, RA-AF, sentry function, historical index, and frequency content (partial power) can help understand various damage processes. These metrics can identify different test phases based on changing trends in event rate and RA-AF over time. The historical index reveals the patterns of significant events, while the b-value indicates micro and macro cracking during damage progression. Frequency analysis can effectively classify various damage mechanisms associated with different material components. The research involves four RC beams, one serving as a control beam, while the other three undergo partial damage before being flexurally strengthened with FRCM using different methods. These beams are then subjected to monotonic four-point bending loading. In addition to AE-based health monitoring, the digital image correlation (DIC) technique is used to monitor surface strain. 2. Experimental Program 2.1. Materials M35 concrete and 16 mm Fe 500D TMT rebars are used during the casting of the RC beams. Two pre-impregnated carbon FRCM mesh layers with 400 GSM weight are utilized to strengthen the pre-damaged RC beam. Four beams were studied, one of which is a control beam, and the other three were pre-damaged and then strengthened with two layers of FRCM. All the beams were under-reinforced and were subjected to four-point bending loading. Three beams vary by the type of strengthening methodology (Two on-site methodologies with anchorage and one conventional methodology). The properties of the materials are given in Table 1. All beams are 200 x 300 in cross-section and 3 meters long and are reinforced with two 16mm bars on the top and bottom each. Shear reinforcement with a constant spacing of 150 mm throughout is provided to avoid shear failure of all beams.