Papers by Keyword: FRP

Abstract: Fiber Reinforced Polymer (FRP) has been used as one of the repair or strengthening materials for deteriorated concrete structures. However, the elastic properties of FRP materials cause a limitations on the ductility of the reinforced concrete structure. This research focuses on the study of the behavior of reinforced concrete beams strengthened using a hybrid Carbon-Glass Fiber Reinforced Plastic (Hybrid FRP). Hybrid FRP is a combination of two layers of FRP that have different elastic modulus, namely Glass Fiber and Carbon Fiber. The objective of using hybrid composites is to obtain a combined elastic mode behavior from two kind of fibers. Flexural testing of reinforced concrete beams with FRP hybrid reinforcement was carried out to study the flexural behavior and also the effectiveness of strengthening. The test material is a reinforced concrete beam with dimensions of 150 mm x 200 mm x 3300 mm. Two types of beams were prepared, namely control beams (BN) and beams with FRP Hybrid strengthening (BGC). The composition of the FRP hybrid was 100% of Glass fiber and 40% of Carbon fiber to the width of the beam. The test results show that the beam with FRP hybrid strengthening has a moment capacity of 12% higher than the control reinforced concrete beam (BN). The mode of failure of the BN beams was the crushing of the concrete that was initiated by yielding of the steel reinforcement. For BGC beams, failure mode was in the form of debonding of the hybrid FRP layer.

Abstract: This research explores the development of advanced materials known as natural fiber reinforced polymer (FRP) composites with the aim of enhancing overall quality of life. Hybrid fibers derived from durian/luffa fibers were integrated into Polyethylene (PE) matrices to fabricate hybrid natural fiber PE composites. The study involves a comprehensive examination of these composites through tensile testing, scanning electron microscopy (SEM), and Fourier-Transform Infrared (FTIR) analysis. Results indicate that the tensile strength of the durian/luffa PE (DLPE) composite surpasses that of neat PE laminates, highlighting its superior stress tolerance. Overall, the composites exhibit specific tensile strength and modulus, contributing to the creation of lightweight materials compared to neat PE. SEM analysis indicates satisfactory fiber-to-matrix bonding with room for improvement, as observed gaps between fibers and matrix are present. FTIR analysis uncovers constituents in the chemical composition of durian and luffa fibers. The inclusion of natural fibers as an alternative to synthetic counterparts aligns with Sustainable Development Goals (SDG) standards. This research underscores the feasibility and benefits of fiber hybridization, emphasizing improved mechanical strength, environmental sustainability, and cost efficiency.

Abstract: This paper presents a study from an ongoing research project on the bond performance of flexural prisms strengthened using carbon-fiber-reinforced polymer (CFRP) laminates. The primary objective is to evaluate the effect of normal-strength concrete (NSC – 30MPa) and high-strength concrete (HSC - 50MPa) on the bond performance of plain concrete prisms notched at the mid-span and strengthened using CFRP laminates. Six of the twelve plain concrete prisms were strengthened using CFRP laminates, while the remaining prisms were unstrengthened to serve as control specimens. After achieving 28 days of curing in standard lab conditions, all prisms were tested under a four-point bending test. The ultimate mid-span deflection, maximum and ultimate strains at the mid-span, strain distribution at different positions along the length of the laminate, and bond/shear stress versus slip were analyzed to evaluate the bond performance of flexural prisms. The average ultimate load-carrying capacities and mid-span deflection of the NSC and HSC groups were 31.33 and 35.02 kN and 0.55 and 1.54 mm, respectively. The average CFRP strain values at the mid-span corresponding to the ultimate load were 5005 and 3544 με for the NSC and HSC groups, respectively. The maximum attained bond-stress values for NSC and HSC groups were 1.71 and 1.42 MPa, respectively. The corresponding values for slip at maximum bond stress are 0.27 and 0.24 mm for the two groups, respectively. It was concluded from the study that the concrete compressive strength has minimal effect on the flexural bond performance of concrete prisms externally bonded with CFRP laminates.

Abstract: Fiber-reinforced polymer (FRP) composites have increasingly been used in the past 40 years. They are ideal option for external strengthening of reinforced concrete (RC) structures due to their superior properties, including the high strength-to-weight ratio and ease of installment. The structural behavior of strengthened RC beams and the efficiency of the external FRP applied are both highly dependent on the bond performance between FRP and concrete. This paper presents an experimental study on the bond slip behavior of carbon fiber reinforced polymer (CFRP) sheets, applied to concrete structures under room temperature conditions. The experimental investigation involved the strengthening of three concrete prism specimens with CFRP sheets. The prism specimens were tested under a three-point bending setup. The bond slip phenomenon was analyzed using strain gauge readings attached to the CFRP laminate before testing. The calculated model aimed to accurately capture the bond slip behavior and its associated parameters, including the maximum shear stress, and maximum slip. These parameters were compared with theoretically derived formulas available in the literature. The theoretical equations overestimated the FRP stresses when compared to experimental measurements. The comparative analysis assesses the accuracy and reliability of the theoretical derivations by benchmarking it against the experimentally derived bond-slip model for CFRP-to-concrete joints.

Abstract: In recent decades, fiber-reinforced polymer (FRP) is being used more and more to make concrete structures stronger. In this study, nonlinear finite element (FE) analysis was used to model and compare the influence of curvature performance on the behavior of the simply-supported RC curved soffit reinforced girders strengthened with fiber-reinforced polymer plates (CFRP) with a curve height of 5 to 130 mm. In this study, two models with different heights of curve (5 and 130 mm) and references for each model were used. Each model had dimensions that were similar to those of the models used in the program in terms of cross-sectional area and effective span. Simulations were done on the girders to find out how the load moved in relation to the mean range, the failure load, and the failure mode. This was done so that the effect of curvature on the performance of this type of structural element could be understood. The results show that the girder of height of curve is 5 mm more than 130 mm of the analytical ultimate load compared with that experimentally with a difference of only 4.5%, and 4.2% respectively. The load-displacement curves of the experimental tests were accurately simulated with the help of a nonlinear finite element model.

Abstract: Geopolymer is an innovative cement substitute constructed of alkali-activated cementitious materials (AACMs). Researchers interested in improving concrete's structural resistance, toughness, and flexure tensile strength have turned their focus to geo-polymer concrete binders. To completely understand how geopolymer binders act under these circumstances, it is necessary to investigate their behavior when exposed to multiaxial stress states. The purpose of this review is to examine geopolymer cement in depth and to get a better understanding of its mechanical characteristics. In this analysis, we see that Geopolymer concrete, in particular its compressive and tensile strengths, provides higher resilience. GPC is an eco-friendly material since it reduces emissions and requires less water for curing. Incorporating hybrid polypropylene and steel fibers to ternary mixed geopolymer concrete improves its mechanical qualities.

Abstract: This paper presents an experimental study to investigate the effect of core drilling on the Reinforced Concrete (RC) column capacity. It also discusses how to restore the drilled RC column capacity. The experimental work consists of seven half-scale short rectangular concrete columns with cross section in width and depth equal to 160 and 300 mm, respectively. All specimens have the same column total and clear height which is equal to 1900 and 1300 mm, respectively. On loading at 40% of column load capacity, the core has been taken to stimulate what happens in nature where core is drilled in buildings. The discussion presents the different strengthening techniques for the core drilling zone to restore the un-voided column capacity, strengthen techniques such as using Carbon Fiber Reinforcement Polymer (CFRP) and anchored steel plates. The study showed good agreement of the results. Finally, recommendations are given for the reduction in the RC column load carrying capacity under the effect of core hole.

Abstract: This paper presents a critical review of the most established analytical models for the prediction of the compressive strength of FRP and FRCM-confined masonry columns. In particular, two types of fibres are analysed, i.e. glass and basalt. A wide dataset available in the literature is used for the application of the analytical models and for the development of parametric analyses useful for the critical comparison of FRP vs. FRCM confinement technique and glass vs. basalt fibres to be adopted as reinforcement of masonry substrate. The effects of stiffness and strength of the reinforcement, the number of reinforcing layers, the compressive strength of masonry and the cross-section shape are investigated.

Abstract: Externally bonded composites have become an effective alternative for building strengthening in recent years, such as FRP (Fiber Reinforced Polymer) and FRCM (Fiber Reinforced Cementitious Matrix) can be utilized in this retrofitting strategy. For masonry structure, curved members are very common and tend to be the weakest parts of the system, meanwhile exhibiting bond behavior differently from that of flat surfaces. In this article, a simplified model consisted of an elastic composite strip and inelastic brittle substrate was adopted, based on which a fully analytical approach is developed for describing the debonding mechanism of FRP/FRCM strengthened curved surface under shear force. This approach requires few parameters, and can be realized with limited computational cost in a standard MATLAB environment, while providing a stable solution. This approach was then validated against numerical method and experimental data available in literatures, proving its effectiveness and reliability.

Abstract: Fibre-reinforced polymers have been widely used to strengthen masonry structures which owning to their high strength-weight ratio and good durability. The interfacial strength between masonry substrate and FRP plays an essential role in the structural bearing capacity. Plenty of experiments have revealed that interfacial failure typically occurs within a thin layer of masonry near the bond line. The mortar joint's location in the masonry substrate sample influences the bond strength and failure mode and has not been thoroughly investigated. This work focuses on the effect of mortar joints on the normal bond strength and damage process in the pull-off test. The two-dimensional mesoscale finite element model is set up, and zero thickness cohesive elements (cohesive zone model) are inserted into the inner and interface between different materials. The numerical result shows that the mortar joint in the middle of the masonry substrate sample shows the largest normal bond strength, and next to the groove is the smallest.