PSI - Issue 64

Ali Alraie et al. / Procedia Structural Integrity 64 (2024) 1943–1950 Ali Alraie, Saverio Spadea, Vasant Matsagar/ Structural Integrity Procedia 00 (2019) 000–000

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fibre ropes, such as flax and sisal, were introduced as a partial replacement of steel bars in reinforced concrete beams to reduce the construction cost (Heniegal, 2017). It was observed that replacing up to 50% of the steel reinforcement with fibre ropes has enhanced the deformation capacity factor, maintained the same load capacity factor, and reduced the serviceability factor to about 75% of the control beam (reinforced with steel only). Furthermore, the application of plant-based natural fibre-reinforced polymer (FRP) composites as energy absorbers was investigated by Yan et al. (2017). Their investigation indicated that flax fibre could replace basalt and glass fibres for energy absorber application. Moreover, the carbon-based sustainability index of jute and kenaf natural fibres was found to be the highest owing to better carbon use efficiency (Singh et al., 2018), and the carbon footprint of these fibres was much lower than their synthetic counterparts. Consequently, low-carbon concrete, reinforced with natural fibres obtained from agricultural wastes, with a high level of supplementary cementitious materials (SCMs), was successful in structural applications from both economic and environmental aspects (Perepechay et al., 2021). Most of the previous studies found in the literature have focused on the performance of concrete with discrete short fibres, and few studies have been found on using natural fibre ropes as internal reinforcement and/or external strengthening materials. The use of natural jute fibre (NJF) ropes in the post-tensioning of reinforced concrete beams was found absent in the literature. Hence, this study focuses on the flexural performance of reinforced concrete beams post-tensioned with unbonded NJF ropes and investigates the improvement in behaviour by conducting an analytical investigation, finite element analysis, and experimental campaign. Steel-post-tensioned concrete beams are prone to corrosion; therefore, this study intends to replace the post-tensioning steel cables with NJF ropes while keeping the steel tension reinforcement protected by the concrete. However, further investigation was conducted in the finite element analysis to replace the steel tension reinforcement with basalt fibre-reinforced polymer (BFRP) rebars so that the concrete member becomes steel-free. Hence, the design becomes corrosion-resistant. Utilising jute ropes in the post-tensioning of beams is an innovative technology that may lead to greater sustainability in the construction industry. 2. Materials and Methods The current study focuses on natural jute fibre (NJF) in addition to conventional structural materials such as concrete and steel. To learn more about the proposed material, a prerequisite tension test was required to characterise the mechanical properties of the NJF rope. 2.1. Characterization of Natural Jute Fibre (NJF) Ropes The tension test on the NJF rope samples was conducted in the Multi-Hazard Protective Structures (MHPS) Laboratory at the Indian Institute of Technology (IIT) Delhi (India) to characterise the mechanical properties of the jute rope intended to be used in this study. Several attempts were made to conduct the test. Initially, the NJF rope sample was directly gripped in the universal testing machine (UTM) grips. This resulted in premature failure at the gripping area due to the localisation of stresses from the gripping action. Later on, the sample was tied to jute-tying ropes wrapped around the top and bottom parts of the UTM. This technique has resulted in the relaxation of knots and tying ropes, which has added significant deformation to the actual deflection of the sample, exceeding the maximum travel distance of the moving part of the UTM without reaching the failure of the rope. Finally, the sample was anchored with the help of anchors made from steel tubes surrounding the sample at the gripping zone with a knot made at the end of the rope. The anchors were only the parts gripped, whereas the jute rope was just passing through the anchors. This technique has been performed successfully, and the gauge failure of the rope can be achieved. The gauge length of the rope sample between the two anchors was 600 mm, and the tension test was conducted on three specimens for reliability. The jute rope and stress-strain curves of the three tested samples (S 1, S 2, and S 3) are shown in Fig. 1. It was found that the average tensile strength and elastic modulus of the jute rope were 55.4 MPa and 754.3 MPa, respectively.