Search Results (275)

Basalt-fiber-reinforced polymer (BFRP) composites, utilizing a natural high-performance inorganic fiber, exhibit excellent weathering resistance, including tolerance to high and low temperatures, salt fog, and acid/alkali corrosion. They also possess superior mechanical properties such as high strength and modulus, making them widely applicable in aerospace and shipbuilding. This study experimentally investigated the mechanical properties of BFRP plates under various strain rates (10⁻⁴ s⁻¹ to 10³ s⁻¹) and directions using an electronic universal testing machine and a split Hopkinson pressure bar (SHPB).The results demonstrate significant strain rate dependency and pronounced anisotropy. Based on experimental data, relationships linking the strength of BFRP composites in different directions to strain rate were established. These relationships effectively predict mechanical properties within the tested strain rate range, providing reliable data for numerical simulations and valuable support for structural design and engineering applications. The developed strain rate relationships were successfully validated through finite element simulations of low-velocity impact. Full article

The construction industry is exploring alternatives to traditional steel reinforcement in concrete due to steel’s corrosion vulnerability. Glass Fiber Reinforced Polymer (GFRP) and Basalt Fiber Reinforced Polymer (BFRP), known for their high tensile strength and corrosion resistance, are viable options. This study evaluates the flexural performance of concrete beams reinforced with GFRP, BFRP, and hybrid systems combining these materials with steel, following ACI 440.1R-15 guidelines. Twelve beams were assessed under three-point bending to compare their flexural strength, ductility, and failure modes against steel reinforcement. The results indicate that GFRP and BFRP beams achieve 8% and 12% higher ultimate load capacities but 38% and 58% lower deflections at failure than steel, respectively. Hybrid reinforcements enhance both load capacity and deflection performance (7% to 17% higher load with 11% to 58% lower deflection). However, GFRP and BFRP beams show reduced energy absorption, suggesting that hybrid systems could better support critical applications like seismic and impact-prone structures by improving ductility and load handling. In addition, BFRP beams predominantly failed due to debonding and concrete crushing, while GFRP beams failed due to bar rupture, reflecting key differences in their flexural failure mechanisms. Full article

Despite the strength and ductility of steel reinforcing bars, their susceptibility to corrosion can limit the long-term durability of reinforced concrete structures. Fiber-reinforced polymer (FRP) reinforcing bars made with a thermosetting matrix offer corrosion resistance but cannot be field-bent, which limits flexibility during construction. FRP reinforcing bars made with fiber-reinforced thermoplastic polymers (FRTP) address this limitation; however, their high processing viscosity presents manufacturing challenges. In this study, the Continuous Forming Machine, a novel pultrusion device that uses pre-consolidated fiber-reinforced thermoplastic tapes as feedstock, is described and used to fabricate 12.7 mm nominal diameter thermoplastic composite rebars. Simple bend tests on FRTP rebar that rely on basic equipment are performed to verify its ability to be field-formed. The manual bending technique demonstrated here is practical and straightforward, although it does result in some fiber misalignment. Subsequently, surface deformations are introduced to the rebar to promote mechanical bonding with concrete, and tensile tests of the bars are conducted to determine their mechanical properties. Finally, flexural tests of simply-supported, 6 m long beams reinforced with FRTP rebar are performed to assess their strength and stiffness as well as the practicality of using FRTP rebar. The beam tests demonstrated the prototype FRTP rebar’s potential for reinforcing concrete beams, and the beam load–deformation response and capacity agree well with predictions developed using conventional structural analysis principles. Overall, the results of the research reported indicate that thermoplastic rebars manufactured via the Continuous Forming Machine are a promising alternative to both steel and conventional thermoset composite rebar. However, both the beam and tension test results indicate that improvements in material properties, especially elastic modulus, are necessary to meet the requirements of current FRP rebar specifications. Full article

Glass Fiber-Reinforced Polymer (GFRP) bars are becoming increasingly common in structural engineering applications due to their superior material properties, mainly their resistance to corrosion due to their metallic nature in comparison to steel reinforcement and their improved durability in alkaline environments compared to CFRP and BFRP reinforcement. However, GFRP bars also suffer from a few limitations. One of the main issues that affects the performance of GFRP reinforcing bars is their bond with concrete, which may differ from the bond between traditional steel bars and concrete. However, despite the wide attention of researchers, there has not been a critical review of the recent research progress on bond behavior between GFRP bars and concrete. The objective of this paper is to provide an overview of the current state of research on bond in GFRP-reinforced concrete in an attempt to systematize the existing scientific knowledge. The study summarizes experimental investigations that directly measure bond strength and investigates the different factors that influence it. Additionally, an overview of the analytical and empirical models used to simulate bond behavior is then presented. The findings indicate the dependence of the bond on several factors that include bar diameter, bar surface, concrete strength, and embedment length. Additionally, it was concluded that both traditional and more recent bond models do not explicitly account for the effect of different factors, which highlights the need for improved bond models that do not require calibration with experimental tests. Full article

Fiber-reinforced polymer (FRP) bars have great potential to replace steel bars in the design of reinforced concrete (RC) beams since they have numerous advantages such as high tensile strength and good corrosion resistance. Therefore, many studies including experiments and numerical simulations have focused on the behavior of FRP RC beams. In this paper, a comprehensive overview of previous studies is conducted to provide a thorough understanding about the behavior, the design, and the limitations of FRP RC beams. Particularly, experimental studies on FRP RC beams are collected and reviewed. In addition, the numerical analysis of FRP beams including the finite element (FE) analysis, the discrete element (DE) analysis, and artificial intelligence/machine learning (AI/ML) is summarized. Moreover, the international standards for the design of FRP RC beams are presented and evaluated. Through the review of previous studies, 93 tested specimens are collected. They can be a great source of reference for other studies. In addition, it has been found that the studies on the continuous beams and deep beams reinforced with FRP bars are still limited. In addition, more studies using DE analysis and AI/ML to analyze the response of FRP RC beams under loading conditions should be conducted. Full article

This paper outlines a structural qualification process to assess the use of newly developed high-modulus (HM) glass fiber-reinforced polymer (GFRP) bars with headed ends in the joint between concrete bridge barriers and decks. The main goals of the study are to evaluate the structural performance of GFRP-reinforced TL-5 barrier–deck systems under transverse loading and to determine the pullout capacity of GFRP anchorage systems for both new construction and retrofit applications. The research is divided into two phases. In the first phase, six full-scale Test-Level 5 (TL-5) barrier wall–deck specimens, divided into three systems, were constructed and tested up to failure. The first system used headed-end GFRP bars to connect the barrier wall to a non-deformable thick deck slab. The second system was similar to the first but had a deck slab overhang for improved anchorage. The third system utilized postinstalled GFRP bars in a non-deformable thick deck slab, bonded with a commercial epoxy adhesive as a solution for deteriorated barrier replacement. The second phase involves an experimental program to evaluate the pullout strength of the GFRP bar anchorage in normal-strength concrete. The experimental results from the tested specimens were then compared to the factored applied moments in existing literature based on traffic loads in the Canadian Highway Bridge Design Code. Experimental results confirmed that GFRP-reinforced TL-5 barrier–deck systems exceeded factored design moments, with capacity-to-demand ratios above 1.38 (above 1.17 with the inclusion of an environmental reduction factor of 0.85). A 195 mm embedment length proved sufficient for both pre- and postinstalled bars. Headed-end GFRP bars improved pullout strength compared to straight-end bars, especially when bonded. Failure modes occurred at high loads, demonstrating structural integrity. Postinstalled bars bonded with epoxy performed comparably to preinstalled bars. A design equation for the barrier resistance due to a diagonal concrete crack at the barrier–deck corner was developed and validated using experimental findings. This equation offers a conservative and safe design approach for evaluating barrier–deck anchorage. Full article

The integration of fiber-reinforced cementitious composites (FRCCs) with fiber-reinforced polymer (FRP) bars represents a significant advancement in concrete technology, aimed at enhancing the structural performance of reinforced concrete elements. The incorporation of fibers into cementitious composites markedly improves their mechanical properties, including tensile strength, ductility, compressive strength, and flexural strength, by effectively bridging cracks and optimizing load distribution. Furthermore, FRP bars extend these properties with their high tensile strength, lightweight characteristics, and exceptional corrosion resistance, rendering them ideal for applications in aggressive environments. In recent years, there has been a notable increase in interest from the engineering research community regarding this topic, primarily to solve the issues of aging and deteriorating infrastructure. Researchers have conducted extensive investigations into the structural performance of FRCC and FRP composite systems. This paper presents a systematic literature review that surveys experimental and analytical studies, findings, and emerging trends in this field. A comprehensive search on the Web of Science identified 40 relevant research articles through a rigorous selection process. Key factors of structural performance, such as bond behavior, flexural behavior, ductility performance assessments, shear and torsional performance, and durability evaluations, have been documented. This review aims to provide an in-depth understanding of the structural performance of these innovative composite materials, paving the way for future research and development in construction materials technology. Full article

Titanium alloy/carbon fiber-reinforced polymer (TA1/CFRP) laminates, representing the latest fourth generation of fiber metal laminates (FMLs), is a kind of high-performance composite material. However, the fragility of the fiber/resin and metal/resin interface layers in these composites directly impacts their mechanical properties. To enhance these properties, this paper investigates the preparation process of multi-walled carbon nanotube (MWCNT)-reinforced ultra-thin TA1/CFRP laminates and explores the impact of MWCNT content on the interlayer properties of these ultra-thin TA1/CFRP laminates. Initially, the challenge of dispersing carbon nanotubes using ultrasonic dispersion devices and dispersants was addressed. Vacuum-curing pressure studies revealed minimal overflow at 0.8 bar vacuum. Subsequently, the impact of MWCNT content on interlayer properties was investigated. The results indicated a significant increase in interlayer shear strength and interlayer fracture toughness with MWCNT additions at 0.5 wt% and 0.75 wt%, whereas the interlayer properties decreased at 1.0 wt% MWCNT. Fracture morphology analysis revealed that MWCNT content exceeding 0.75 wt% led to agglomeration, resulting in resin cavity formation and stress concentration. Full article

Reinforced concrete structures often require retrofitting due to damage caused by natural disasters such as earthquakes, floods, or hurricanes; deterioration from aging; or exposure to harsh environmental conditions. Retrofitting strategies may involve adding new structural elements like shear walls, dampers, or base isolators, as well as strengthening the existing components using methods such as reinforced concrete, steel, or fiber-reinforced polymer jacketing. Selecting the most appropriate retrofit method can be complex and is influenced by various factors, including initial cost, long-term maintenance, environmental impact, and overall sustainability. This study proposes utilizing an artificial neural network (ANN) to predict sustainable and cost-effective seismic retrofit solutions. By training the ANN with a comprehensive dataset that includes jacket thickness, material specifications, reinforcement details, and key sustainability indicators (economic and environmental factors), the model was able to recommend optimized retrofit designs. These designs include ideal values for jacket thickness, concrete strength, and the configuration of reinforcement bars, aiming to minimize both costs and environmental footprint. A major focus of this research was identifying the optimal number of neurons in the hidden layers of the ANN. While the number of input and output neurons is defined by the dataset, determining the right configuration for hidden layers is critical for performance. The study found that networks with one or two hidden layers provided more reliable and efficient results compared to more complex architectures, achieving a total regression value of 0.911. These findings demonstrate that a well-tuned ANN can serve as a powerful tool for designing sustainable seismic retrofit strategies, helping engineers make smarter decisions more quickly and efficiently. Full article

The increasing demand for sustainable construction materials has driven the exploration of alternatives to traditional cement-based concrete. In this context, this study investigates a cement-less material, specifically an alkali-activated or geopolymer concrete (GPC), which presents potential environmental benefits. The material has been characterized with respect to both its fresh and hardened properties, providing groundwork for future structural applications. A key focus of the research is the bond behavior between GPC and reinforcing bars, including both steel and non-metallic fiber-reinforced polymer (FRP) bars. The use of non-metallic bars is particularly relevant as they offer the potential to enhance the durability of structures by mitigating issues such as corrosion. Current research lacks comprehensive studies on factors affecting stress transfer at the GPC-reinforcing bar interface, such as bar diameter, bond length, and surface finish. This study aims to expand knowledge on the bond between GPC and steel/FRP rebars through experimental and analytical approaches. The tests, which included different bar types and bond lengths, showed that GPC exhibited similar bond behavior with steel and ribbed glass FRP bars in terms of bond strength and stress-slip curves. The results indicate that GPC exhibits comparable bond strength and stress-slip behavior when reinforced with either steel or ribbed glass FRP bars. Full article

With growing emphasis on sustainable construction, fiber-reinforced polymer (FRP) bars are increasingly being used as alternatives to steel rebars due to their high strength-to-weight ratio, corrosion resistance, and environmental benefits. This study has investigated the bond behavior between FRP bars and concrete of different strength grades under dynamic loading conditions. To analyze the microscopic properties of FRP bar surfaces, the study employs a variety of techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), and non-contact surface profilometry. In addition, X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) measurements, and energy dispersive spectrometry (EDS) are used to further investigate surface characteristics. The results reveal a direct correlation between the resin surface roughness of FRP bars and their wettability characteristics, which in turn influence the cement hydration process. Pull-out tests under different loading rates and concrete strength grades have been conducted to evaluate the bond–slip behavior and failure modes. The results indicate that bond strength increases with increasing concrete strength. Dynamic pull-out tests further reveal that higher loading rates generate heterogeneous stress fields, which limit the deformation of FRP bars and consequently diminish the contribution of mechanical interlock to interfacial bonding. Full article

Recent catastrophic bridge fire incidents have highlighted the critical need for effective post-fire assessment of bridges, thereby challenging the dominant practice of complete replacement following these destructive events. This study investigates the post-fire performance of bare, isolated, and Carbon Fiber Reinforced Polymer (CFRP)-repaired Reinforced Concrete (RC) bridge columns under single-unit truck impact followed by air blast. This extreme loading scenario was deliberately selected given the increased vulnerability of bridge columns to this loading scenario in the recent few years. Three-dimensional Finite Element (FE) models of the structural system and surrounding environment were developed and validated in LS-DYNA. The effectiveness of two in-situ retrofitting schemes in mitigating damage and enhancing structural integrity of three column diameters under the selected multi-hazards was assessed. Results demonstrated that wrapping the bottom half of the column height prevents shear failure and significantly reduces the damage under the coupled impact and blast. In contrast, employing a combination of CFRP bars and externally bonded sheets showed limited enhancement on post-fire impact and blast performance. This study provides critical insights into the feasibility and efficacy of retrofitting bridge columns that have experienced fire, thus laying the groundwork for the reconsideration of current design and rehabilitation protocols. Full article

FRCM (Fabric-Reinforced Cementitious Matrix) composites, while providing an effective alternative to FRP (Fiber-Reinforced Polymer) strengthening systems when epoxy resins cannot be used, typically fail to achieve their full strengthening potential. Research indicates that appropriate mesh anchorage systems can minimize some of the undesirable effects that limit FRCM composite performance. This study investigates the effectiveness of different anchorage systems for PBO (p-Phenylene Benzobis Oxazole) fibers in FRCM composites used for strengthening reinforced concrete slabs. A series of unidirectionally bent RC slabs were tested under four-point bending: an unstrengthened control element, slabs strengthened with PBO-FRCM without anchorage, with bar anchorage (GFRP bar in a groove), and with cord anchorage (PBO cord through the slab). The research focused on analyzing the load–deflection behavior and key strain mechanisms that influence structural performance. The findings indicate that a single layer of PBO-FRCM increases bending capacity, raises yield load, and delays initial cracking. Most significantly, the research reveals substantial differences in composite mesh utilization efficiency. This study confirms that mechanical anchorage, particularly bar anchorage, significantly enhances the effectiveness of PBO-FRCM strengthening systems by delaying composite detachment and allowing for greater utilization of the high-strength fiber material. These results contribute valuable insights for RC slabs using FRCM composite systems and the anchorage of their mesh. Full article

Steel fiber-reinforced polymer (FRP) composite bars (SFCBs) combine the ductility of steel reinforcement with the corrosion resistance and high strength of FRP, providing stable secondary stiffness that enhances the seismic resistance and safety of seawater sea–sand concrete structures. However, the seismic performance of SFCB-reinforced seawater sea–sand concrete beam–column joints remains underexplored. This study presents pseudo-static tests on SFCB-reinforced beam–column joints with varying column SFCB longitudinal reinforcement fiber volume ratios (64%, 75%, and 84%), beam reinforcement fiber volume ratios (60.9%, 75%, and 86%), and axial compression ratios (0.1 and 0.2). The results indicate that increasing the axial compression ratio enhances nodal shear capacity and bond strength, limits slip, and reduces crack propagation, but also accelerates bearing capacity degradation. Higher column reinforcement fiber volumes improve crack distribution and ductility, while beam reinforcement volume significantly affects energy dissipation and crack distribution, with moderate volumes (e.g., 75%) yielding optimal seismic performance. These findings provide insights for the seismic design of SFCB-composite-reinforced concrete structures in marine environments. Full article

This study aims to verify the adaptability of a crack width evaluation method for fiber-reinforced cementitious composite (FRCC) proposed by the authors to various combinations of fiber-reinforced polymer (FRP) bars and FRCCs. As this evaluation method requires bond constitutive laws between FRP bars and FRCC, bond tests between FRP and FRCCs were conducted. The FRP and FRCC combinations used in the bond tests were spiral-type CFRP and GFRP bars with PVA-FRCC, as well as strand-type CFRP bars with aramid–FRCC. The maximum bond stress tended to increase as the rib–height ratio of the spiral-type bars increased. When the rib–height ratio increased by 50%, the maximum bond stress of the CFRP and GFRP bars increased by 11% and 33%, respectively. For aramid–FRCC, the average maximum bond stress in the FRCC with a 0.25% volume fraction was 1.67 times that in mortar, and that in 0.50% was 2.01 times that in mortar. The bond constitutive laws were modeled using the trilinear model. Verifications of the method’s adaptability were conducted using tension tests on prisms made of spiral-type CFRP and GFRP bars with PVA-FRCC. As a result of the tension tests, when the FRP strain reached approximately 0.3%, the crack width was about 0.2 mm for CFRP bars and about 0.1 mm for GFRP bars. Verifications were also conducted using four-point bending tests on strand-type CFRP bar beams with aramid–FRCC. The crack width at the same FRP strain tended to become smaller as the fiber volume fraction of FRCC increased. When the FRP strain reached approximately 0.2%, the average crack width of the mortar specimen was around 0.25 mm, whereas it was about 0.15 mm in FRCC with a 0.25% volume fraction and about 0.10 mm at 0.5%. The test results for FRP strain versus crack width relationships were compared with the calculations using the crack width prediction formula. The test results and calculation results were in good agreement. Full article