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Previous research indicates that lightweight aggregate (LWA) concrete exhibits more brittle failure under compression than conventional normal density (ND) concrete. In contrast, angle-ply fiber-reinforced polymer (FRP) filament-wound tubes filled with ND concrete show significant improvements in strength and deformability compared to hollow tubes. This study evaluates the impact of these tubes on LWA concrete to mitigate its brittle behavior. Sixteen concrete-filled FRP filament-wound tubes (CFFTs) made of ±55° filament-wound glass FRP (GFRP) were tested under axial compression. The GFRP tube's mechanical properties and fiber winding angle of ±55° allowed for a compressive strength enhancement factor ranging from two to five for the CFFTs compared to unconfined specimens. Results also revealed substantial nonlinearity and deformability in the LWA-CFFTs due to the angle-ply tube orientation. An iterative analytical model predicted the CFFT's nonlinear response, validated by experimental data. The findings demonstrate that angle-ply FRP tubes effectively enhance the bearing capacity and deformability of inherently brittle unconfined LWA concrete. [ABSTRACT FROM AUTHOR]

To improve the structural performance of precast assembled concrete piers under earthquake, we designed and manufactured two piers confined by carbon fiber reinforced polymer (CFRP) sheets (SPCC1, SPCC2), two piers confined by glass fiber reinforced polymer (GFRP) tubes (SPCG6, SPCG10), and one comparison pier (SPC). The column and bent cap connections were designed with a monolithic construction, whereas the column and pile cap connections had precast joints with grouted sleeves. The effects of the CFRP and GFRP on the seismic performance of the specimens were studied using a quasi-static test and a fiber model based on OpenSees. The failure modes of the specimens included concrete crushing in the plastic hinge zone and buckling fracture of the longitudinal reinforcement. A CFRP tensile fracture occurred in the plastic hinge zone at the top and bottom of the piers; however, damage to the GFRP tubes was minor. Compared with sample SPC, the maximum bearing capacities of SPCG6, SPCG10, SPCC1, and SPCC2 increased by 8.4%, 3.1%, 15.0%, and 4.8%, respectively. At 7% displacement, the residual bearing capacities of SPCG6, SPCG10, SPCC1, and SPCC2 increased by 103.3%, 90.4%, 36.7%, and 82.8%, respectively, compared with SPC. At 6% and 7% displacement, the average stiffness of the CFRP/GFRP-confined specimens increased by 46.2%/58.9% and 59.8%/96.8%, respectively, compared with that of the unconfined specimen. The curvature results also showed that the confined pier exhibited a better flexural performance in most loading processes. The test and simulation results showed that the connection strength of the grouted sleeve in the precast structure should be ensured, and the reinforcement ratio of the pier should be prioritized, followed by an appropriate improvement in the compressive strength of the concrete. The constraint range of the FRP at twice the height of the plastic hinge zone was sufficiently conservative to ensure that the pier maintained good seismic performance under a high axial compression ratio. In practical engineering, the use of a GFRP tube as a template for a prefabricated pier is recommended, and a CFRP sheet is used to strengthen the plastic hinge area of an existing pier with insufficient seismic ability. [ABSTRACT FROM AUTHOR]

The shear thickening fluid (STF) impregnated Kevlar fabric coating glass fiber reinforced plastic (GFRP) composite structure has both wearing comfort and high protective ability, which will provide guidance for the development of new protective products. In this study, STF with SiO2 mass fraction of 34% was prepared, the quasi-static/dynamic mechanical behavior of STF, Kevlar and STF impregnated Kevlar fabric coating GFRP were carried out by the high-speed impact experiments, respectively. At the same time, the damage characteristics and energy absorption properties of the composite structure are analyzed by integrating experimental data with numerical simulation. The results showed that the composite structure makes the energy absorption capacity of GFRP improved. STF impregnated 4 layers of Kevlar fabric coating GFRP composite structure was impacted by the projectile at a speed of 244 m/s, and the composite structure consumes 1.54 times the energy of single GFRP laminates. The resistance of composite structures can be improved by placing more layers of Kevlar fabric behind GFRP laminates. The evaluation of the target's bullet resistance cannot solely rely on the energy consumed by the projectile. A portion of the energy is transferred to the obstacle that impedes the target's motion. [ABSTRACT FROM AUTHOR]

The adoption of fiber-reinforced polymer (FRP) bars in concrete structures has increased due to their superior mechanical properties and durability. However, the compressive response of FRP bars at high temperatures remains unclear. This article presents an experimental study on the behavior of glass FRP (GFRP) and basalt FRP (BFRP) bars subjected to compressive loads at different elevated temperatures and deformation rates. The study considers four different temperature conditions: ambient temperature (25 °C), 50 °C, 100 °C, and 150 °C, and two different deformation rates: 0.5 mm/min and 1000 mm/min. Digital Image Correlation (DIC) was used to accurately measure strains at high temperatures by generating a suitable speckle pattern over the specimen surface for full-field deformation measurements. The study results revealed that the modulus of elasticity and compressive strength of both GFRP and BFRP bars degraded as the temperature increased from 25 °C to 150 °C. The compressive strength reduction was higher at 150 °C compared to 100 °C, and the reduction was more significant for BFRP bars than GFRP bars. The compressive strength of GFRP bars was comparable under both strain rates for all temperature conditions. However, the elastic modulus of the bars showed a slight variation between the different load rates, especially at an elevated temperature of 150 °C. For the BFRP bars, the study found that different strain rates at ambient temperature resulted in significant deviation in the compressive strength and modulus of elasticity results. At higher temperatures, the reduction in mechanical properties was more pronounced. In summary, the study provides valuable insights into the behavior of GFRP and BFRP bars under compressive loads at elevated temperatures, which is useful for designing and assessing the performance of FRP-reinforced structures under fire conditions. [ABSTRACT FROM AUTHOR]

Fiber‐reinforced polymer (FRP) rebars have become an attractive alternative for replacing steel reinforcement due to their superior corrosion resistance. Columns reinforced with GFRP rebars can fail in a brittle manner than those reinforced with steel rebars. Adding discrete fibers in GFRP‐reinforced concrete (RC) columns can improve its ductility by bridging the cracks formed in concrete. Both steel and synthetic discrete fibers can be combined to form hybrid fiber‐reinforced concrete (HFRC) which synergizes the advantages of both fiber types. An analytical approach is presented here to estimate the axial compression (P) and bending moment (M) interaction behavior of FRC GFRP columns. Moment‐curvature analysis using suitable constitutive relations for concrete and GFRP bars under compression and tension is adopted. Bending moment capacity at different axial compression loads is established. Later, P–M interaction curves for square RC columns with GFRP rebars and discrete fibers are obtained and validated with test results. After that, a parametric study is carried out to understand the effect of concrete strength, amount of reinforcement, and different fiber dosages for GFRP RC columns. Results show that adding fibers can improve the bending and compression capacities at all combinations of axial and bending loads. The axial compression and bending capacity of the steel RC and GFRP columns with equal reinforcement ratios showed that GFRP HFRC had higher capacity than steel RC column sections under combined axial and bending loads. [ABSTRACT FROM AUTHOR]

Studying the mechanical responses of GFRP and aluminum samples under varying loads is crucial for developing methods to enhance their mechanical properties. This research investigates the impact of z-pinning on single-lap adhesive joints through low-velocity shear impact tests. The study involves testing two types of joints: single-lap adhesive joints and single-lap hybrid pin-adhesive joints with six reinforcing pins, subjected to drop weight tests at load levels of 22.5, 27.5, and 32.4 J. The findings demonstrate that z-pinning can increase the joints' load-bearing capacity by up to 18.87% and energy absorption by 20.58%. This enhancement is attributed to the additional composite substrate layers in the hybrid joint, which help absorb impact loads. In contrast, in the single-lap adhesive joint, only the layer adjacent to the adhesive bears the impact load. Observations from the tests indicate that in the single-lap adhesive joint, the first composite layer next to the adhesive undergoes complete delamination, whereas in the hybrid joint, all laminates fracture at the steel pins. In summary, this study underscores the significant potential of z-pinning to improve single-lap adhesive joints, providing an innovative approach to enhance their load-bearing capacity and energy absorption. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced polymer (GFRP) composite tubes have become increasingly popular in crashworthiness applications. On the other hand, square section GFRP tubes are prone to damage in a catastrophic failure mode in the early stages of the crushing process. At this point, triggering mechanisms have great potential to ensure deformation in progressive mode and improve the compression performance of GFRP tubes. Motivated by these facts, this paper aims to optimize the compression performance of square GFRP tubes by implementing notch‐type triggering mechanisms. The effects of notch width, number and length on the axial compression response of tubes were investigated to determine the optimal trigger configurations that would maximize specific energy absorption (SEA) and minimize peak crushing force (PCF). Experiments were conducted based on Taguchi L9 orthogonal array design, and Taguchi coupled Weighted Aggregated Sum Product Assessment (WASPAS) method was employed for optimizing multiple responses. The optimization results revealed that the proposed trigger mechanisms induced progressive crushing by preventing catastrophic failure, thereby significantly improving the compression performance of GFRP tubes. In particular, the results showed that the PCF of intact GFRP tube decreased by up to 38%, while SEA increased by up to 130% with the help of proposed trigger mechanism. Highlights: The compression performance of square GFRP tubes improved by notch‐type triggering.The notch width, length and number were chosen as design parameters.Taguchi experimental design was used to find the best configuration of design parameters.The optimum configurations were examined through the entropy‐WASPAS approach.The results revealed that significant improvements can be achieved using trigger mechanism. [ABSTRACT FROM AUTHOR]

Background: Glass fiber-reinforced polymer (GFRP) bars offer a superior alternative to steel bars in concrete reinforcement but are associated with wider cracks and higher deformation rates. This study introduces a novel approach by combining steel fibers (SFs) and carbon nanotubes (CNTs) to address these drawbacks and enhance the performance of GFRP-reinforced concrete beams. The unique contribution of this study lies in the simultaneous use of SFs and CNTs, which has not been extensively investigated, particularly in the context of GFRP-reinforced concrete. The study involved testing three sets of nine specimens with different concrete mixtures and reinforcement forms. Results: The results showed that adding 0.04% CNTs by cement weight and 0.6% SFs by volume fraction significantly improved the mechanical performance of GFRP and steel reinforced beams. GFRP reinforced beams with CNTs and SFs exhibited a reduction in crack width, a 20% increase in load-carrying capacity, and a 25% reduction in deflection compared to reference specimens. Scanning electron microscope analysis further revealed that CNTs effectively enhanced tensile load transfer, improving flexural behavior of the beams. The finite element analysis using ANSYS confirmed the experimental findings, highlighting the improved stress distribution in the modified concrete mixtures. Conclusions: Incorporating SFs and CNTs in concrete significantly improves the mechanical performance of GFRP-reinforced beams, making them more durable and resilient. These findings suggest that the proposed approach can enhance the longevity and sustainability of concrete structures, particularly in dynamic load applications such as bridges and high-rise buildings. Further experimental and analytical studies are recommended to assess the practical implications and cost-effectiveness of these materials in large-scale construction projects. [ABSTRACT FROM AUTHOR]

Purpose: Glass fiber reinforced polymer (GFRP) composite structures are extensively utilized across the globe due to their lightweight, corrosion resistance, high specific strength and stiffness. Generally, fatigue failures are common in composite structures such as aircraft structures, mechanical components, windmill structures, etc. The crack initiates and propagates in relative orientation between the crack and loading direction which adversely affects the performance of composite structures. Therefore, it is essential to detect the crack location and orientation to avoid catastrophic failure. This research article explores the investigation of transverse cracks with different orientations in GFRP composite beams using a modal data-based Artificial Neural Network (ANN). Methods: The composite beam laminate is fabricated using vacuum-assisted resin transfer molding with bi-directional GFRP lamina. Crack with consistent depth and triangular shape made on the specimen using a hacksaw. Experimental modal analysis is carried out on four beam specimens with different damage conditions such as without crack and transverse crack with 30, 60, and 90-degree orientations under cantilever boundary conditions. Further, ANN is applied to the modal parameters to predict the frequency response functions (FRFs). Results: To comprehend the specimen's behavior for notable changes, modal parameters such as natural frequencies, mode shapes, damping ratios and FRFs are acquired and briefly examined for various experimental cases. Then, FRFs for all four cases are predicted using ANN, and the accuracy of the model is computed. Conclusion: It is observed that for the fundamental mode, natural frequencies decrease and damping ratios increase respectively with the formation of crack. The predicted FRFs using ANN have agreed well with the experimental FRFs for all different criterion. [ABSTRACT FROM AUTHOR]

In this study, the analysis of reinforced concrete (RC) beams strengthened with Fiber Reinforced Polymer (FRP) composites against bending and shear loads was carried out with the finite element technique, using ABAQUS software, which is widely used in simulating experimental circumstances in numerical studies. It has been reported that buildings in areas damaged by earthquakes are generally constructed using low-strength concrete and inadequate reinforcement. Additionally, construction errors also contribute to reducing the load-bearing capacity of structural elements. For this purpose, nine rectangular cross-section RC beams were experimentally constructed using low-strength concrete and inadequate bending and shear reinforcement. These beams were strengthened by wrapping them in different configurations with Carbon and Glass FRP (CFRP and GFRP) composites to resist shear and bending forces in both transverse and longitudinal directions, and their load-displacement curves were obtained. Subsequently, a three-dimensional Finite Element Model (FEM) was created to validate the experimental results. The FEM validation demonstrated high accuracy in replicating experimental outcomes, emphasizing the influence of mesh size, dilation angle, and concrete constitutive models on simulation fidelity. Parametric studies revealed that increasing longitudinal reinforcement diameters had minimal effect on load capacity but highlighted the critical role of transverse reinforcement, as reducing stirrup spacing significantly improved load-bearing capacity. GFRP-reinforced beams exhibited superior ductility and a 15% higher strength compared to CFRP, suggesting their suitability for applications demanding enhanced displacement capacity. Furthermore, the findings underline the need for refined FEM models to better capture inclined fiber orientations and optimize structural reinforcement strategies. [ABSTRACT FROM AUTHOR]

Glass Fiber-Reinforced Composite (GFRP) has found widespread use in engineering structures due to its lightweight construction, high strength, and design flexibility. However, pure GFRP beams exhibit weaknesses in terms of stiffness, stability, and local compressive strength, which compromise their bending properties. In addressing these limitations, this study introduces innovative square GFRP beams infused with gypsum-based composites (GBIGCs). Comprehensive experiments and theoretical analyses have been conducted to explore their manufacturing process and bending characteristics. Initially, four types of GBIGC—namely, hollow GFRP beams, pure gypsum, steel-reinforced gypsum, and fiber-mixed gypsum-infused beams—were designed and fabricated for comparative analysis. Material tests were conducted to assess the coagulation characteristics of gypsum and its mechanical performance influenced by polyvinyl acetate fibers (PVAs). Subsequently, eight GFRP square beams (length: 1.5 m, section size: 150 mm × 150 mm) infused with different gypsum-based composites underwent four-point bending tests to determine their ultimate bending capacity and deflection patterns. The findings revealed that a 0.12% dosage of protein retarder effectively extends the coagulation time of gypsum, making it suitable for specimen preparation, with initial and final setting times of 113 min and 135 min, respectively. The ultimate bending load of PVA-mixed gypsum-infused GFRP beams is 203.84% higher than that of hollow beams, followed by pure gypsum and steel-reinforced gypsum, with increased values of 136.97% and 186.91%, respectively. The ultimate load values from the theoretical and experimental results showed good agreement, with an error within 7.68%. These three types of GBIGCs with significantly enhanced flexural performance can be filled with different materials to meet specific load-bearing requirements for various scenarios. Their improved flexural strength and lightweight characteristics make GBIGCs well suited for applications such as repairing roof beams, light prefabricated frames, coastal and offshore buildings. [ABSTRACT FROM AUTHOR]

This study examines how structural discontinuities created during production affect glass fiber-reinforced composite plates. Due to geometrical constraints, the composite microstructure's discontinuities can be categorized as inter-ply and intra-ply. Material testing was conducted at the coupon level as an initial step to ascertain material characteristics. Two full-scale models of intra-ply composite samples were manufactured by employing layers of glass fiber-reinforced prepregs. Discontinuities were generated in the samples using a computer numeric control cutter and then manually applied. The discontinuities' impact on the composite laminate's mechanical properties was assessed through full-scale pieces using three-point bending quasi-static tests. Servo-hydraulic actuators were used to conduct tests on the items. The experimental test results were compared with CAE analysis predictions by evaluating sectional fiber volume fraction. The characteristics of local discontinuities were analyzed using a microscope to enhance the findings of the CAE model. This comprehensive approach offers insights into the intricate connection between internal structural inconsistencies and the mechanical properties of continuous glass fiber-reinforced materials. It supports optimizing composite manufacturing processes and improves composite parts' structural reliability. Dislocation areas were found to result in the formation of resin-rich zones in this investigation. The exothermic curing process in the component's zones results in elevated temperatures, leading to a color change in the resin from clear to yellow. The yellow areas are easily recognizable and show decreased mechanical durability. [ABSTRACT FROM AUTHOR]

This paper presents a study on manufacturing a range of hybrid laminated structures made of thermoplastic polyurethan (TPU), glass fibre reinforced plastic (GFRP), styrene-butadiene rubber (SBR) and metal mesh materials, and further on investigating the structural response of the TPU based composite sandwich laminated structures. These laminated structures were tested under quasi-static perforation and low velocity impact loading to determine their structural responses and energy absorption characteristics. It has been shown that three-layer and five-layer laminates with lay-ups of GFRP-TPU-GFRP or TPU-GFRP-TPU and GFRP-TPU-GFRP-TPU-GFRP or TPU-GFRP-TPU-GFRP-TPU subjected to quasi-static perforation demonstrate an increased peak load and stiffness with the core thickness from 1 to 4 mm. Also, the TPU core laminates show a superior ductility in comparison to their GFRP core counterparts. The energy absorption values of the three-layer and five-layer TPU and GFRP based laminated structures under low velocity impact are higher than those under quasi-static loading due to strain-rate effect. However, the hybrid laminates with SBR and wire mesh as a core do not give much improvement on the impact perforation resistance of the laminates with the different size of wire mesh, as metal mesh plays a less important role in the laminated structures to resist perforation. In overall, TPU-GFRP-TPU-GFRP-TPU structure with 4mm thick GFRP core demonstrates the highest peak force, and the GFRP-TPU-GFRP-TPU-GFRP structure with 4mm thick TPU core offers the highest energy absorption. [ABSTRACT FROM AUTHOR]

This study investigates the influence of various transverse reinforcement configurations on the torsional performance of glass fiber reinforced plastic (GFRP) reinforced concrete beams. A comprehensive experimental investigation includes five specimens, each characterized by unique transverse reinforcement designs in terms of stirrup spacing and inclination angles. The implementation of transverse torsional reinforcements within the beams exhibited a remarkable post-cracking hardening response, contributing to enhanced strength recovery. The experimental findings are subsequently compared with a reliable three-dimensional finite element model developed using the ABAQUS software. Finally, a parametric study is conducted to examine the influence of concrete and GFRP bar strength, along with longitudinal and transverse reinforcement ratios, on the torsional behavior of GFRP reinforced concrete beams. The results emphasize the significant impact of concrete tensile strength and transverse reinforcement on the cracking torque, while the parameters related to longitudinal reinforcement have only marginal effects. [ABSTRACT FROM AUTHOR]

Concrete columns with hollow-core sections find widespread application owing to their excellent structural efficiency and efficient material utilization. However, corrosion poses a challenge in concrete buildings with steel reinforcement. This paper explores the possibility of using glass fiber-reinforced polymer (GFRP) reinforcement as a non-corrosive and economically viable substitute for steel reinforcement in short square hollow concrete columns. Twelve hollow short columns were meticulously prepared in the laboratory experiments and subjected to pure axial compressive loads until failure. All columns featured a hollow square section with exterior dimensions of (180 × 180) mm and 900 mm height. The columns were categorized into four separate groups with different variables: steel and GFRP longitudinal reinforcement ratio, hollow ratio, spacing between ties, and reinforcement type. The experimental findings point to the compressive participation of longitudinal GFRP bars, estimated to be approximately 35% of the tensile strength of GFRP bars. Notably, increasing GFRP longitudinal reinforcement significantly improved the ultimate load capability of hollow square GFRP column specimens. Specifically, elevating the ratio of GFRP reinforcement from 1.46% to 2.9%, 3.29%, 4.9%, and 5.85% resulted in axial load capacity improvements of 32.3%, 43.9%, 60.5%, and 71.7%, respectively. Specifically, the GFRP specimens showed a decrease in capacity of 13.1%, 9.2%, and 9.4%, respectively. Notably, the load contribution of steel reinforcement to GFRP reinforcement (with similar sectional areas) was from approximately three to four times the axial peak load, highlighting the greater load participation of steel reinforcement due to its higher elastic modulus. In addition, the numerical modeling and analysis conducted using ABAQUS/CAE 2019 software exhibited strong concordance with experimental findings concerning failure modes and capacity to carry axial loads. [ABSTRACT FROM AUTHOR]

To promote the application of molybdenum tailings as the fine aggregate in concrete in construction engineering and verify the feasibility of fiber-reinforced polymer (FRP) material for strengthening molybdenum tailings concrete columns, this study takes a short circular molybdenum tailings concrete column reinforced by glass FRP (GFRP) as the research object. The influences of the molybdenum tailings content (0%, 25%, 50%, 75%, and 100%), the concrete grade (C30, C40, and C50), and the layer number (0, 1, and 2) of the GFRP sheet on the axial compressive capacity of the molybdenum tailings concrete column are investigated. The experimental phenomena and failure modes of the unreinforced and GFRP-reinforced columns are analyzed. The axial compressive strengths of the unreinforced and GFRP-reinforced columns are then compared. The load–strain curve and load–displacement curve of typical molybdenum tailings concrete columns are presented. Subsequently, six classical strength models for FRP-reinforced concrete are used to calculate the axial compressive strength of the confined specimens. The results show that the best classical model has a predictive accuracy with an absolute relative deviation (ARD) of 8.5%. To provide a better prediction of the compressive strength of the GFRP-reinforced molybdenum tailings concrete column, the best classical model is further improved, and the ARD of the modified model is only 5.87%. [ABSTRACT FROM AUTHOR]

Continuous reinforced concrete (RC) beams cast in place are commonly used in construction; however, there is a notable gap in the literature regarding the performance of continuous RC beams strengthened with fiber‐reinforced polymer (FRP) sheets. Strengthening RC beams with FRP sheets typically leads to reduced ductility and moment redistribution capacity due to the linear stress–strain behavior of FRP materials compared to non‐strengthened RC beams. Addressing this gap, this study explores the feasibility of enhancing the mechanical properties and ductility of strengthened elements through a hybrid approach, combining carbon‐fiber‐reinforced polymer (CFRP) and glass‐fiber‐reinforced polymer (GFRP) sheets. An experimental program was conducted, retrofitting two continuous two‐span RC beams (250 × 150 × 6000 mm) with hybrid CFRP‐GFRP (HCG) sheets. Concentrated loads were applied at the center of each span, and comprehensive data on strains in FRP sheets, longitudinal reinforcements, and crack propagation patterns were recorded and meticulously analyzed. The outcomes demonstrated that employing HCG sheets for strengthening RC continuous beams significantly improves ductility, load‐carrying capacity, and moment redistribution, surpassing the performance of beams strengthened with either CFRP or GFRP sheets. To ensure accurate predictions of the flexural response, an analytical model was developed and rigorously verified using the experimental results. The model takes into account the strain compatibility condition and provides insights into the behavior of continuous RC beams strengthened with CFRP, GFRP, and HCG sheets. This research contributes valuable knowledge to the understanding of FRP sheet strengthening techniques, emphasizing the efficacy of HCG sheets for achieving enhanced structural performance in continuous RC beams. [ABSTRACT FROM AUTHOR]

Compressive testing of specimens taken from relatively thin composite plates is difficult, especially due to the occurrence of buckling. To prevent buckling, the central portion of the specimens used for the compression test has smaller dimensions, and the specimens can be guided along their entire length. For these reasons, optical methods, such as digital image correlation (DIC), cannot be used for the compression test and strain rosettes cannot be glued onto the samples to determine Poisson's ratio. In this study, compression tests of a glass fiber-reinforced polymer (GFRP) were conducted using both the ASTM D695 (Boeing version) and a newly proposed method. The new method involves using special specimens that allow T-type rosettes to be bonded to determine Poisson's ratio, whose value of 0.14 was thus determined. SEM images of the failure surfaces were presented and interpreted. A finite element analysis (FEA) of the specimens tested in compression is also presented. The first analyzed case considers the homogeneous and orthotropic composite, loaded with a uniformly distributed force. The normal stress in the central section of the specimen, determined with FEA, has an error of 6.52% compared to that determined experimentally. Additionally, the strain in the center of the strain gauge, determined with FEA, has an error of 4.76% compared to the measured one. In the second case studied with FEA, the sample is loaded with a quasi-concentrated force, which can move in the direction of the symmetry axes of the cross-section, to study the effect of the eccentricity of the compression force on the state of stress. It was shown that the eccentricity of the force has a great influence: the stress distribution in the section of the specimen becomes strongly non-uniform. For a force eccentricity of 0.4 mm in the direction of the OX axis, the minimum stress decreases by 53.7%, and the maximum stress increases by 55.4%. In order to analyze the influence of some manufacturing defects, two other cases were analyzed by FEA, in which it was assumed that the thicknesses of the outer resin layers were modified, making them asymmetrical. For this final FEA, the specimen was considered to be composed of laminates. These results demonstrate the special attention that must be paid to the centric application of force in compression testing. [ABSTRACT FROM AUTHOR]

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This paper aims to investigate the effect of glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) strengthening materials on the static and dynamic behavior of reinforced concrete (R/C) beams subjected to progressive damage. Four identical beams, each strengthened with either GFRP or CFRP, are tested under a cyclic quasi-static loading pattern. Impact hammer tests are performed for undamaged states and various damage levels of the beams. The dynamic test data are analyzed using the Enhanced Frequency Domain Decomposition (EFDD) method to estimate the dynamic characteristics of the beams. In this context, the first three vibration modes in both vertical and horizontal directions are considered. Strengthening is applied to both pre-damaged and undamaged beams, enabling a comparison of their performance before and after the strengthening procedure. Beams strengthened with CFRP exhibit a higher load-bearing capacity and stiffness but also fail at lower displacement levels compared to those strengthened with GFRP, which demonstrate more ductile behavior. Furthermore, the modal frequency ratios indicate that the first vibration mode is more sensitive to damage than the second and third modes. This study highlights the effectiveness of both strengthening materials in enhancing the structural performance of both undamaged and damaged beams. [ABSTRACT FROM AUTHOR]

In this study, the analysis of reinforced concrete (RC) beams strengthened with Fiber Reinforced Polymer (FRP) composites against bending and shear loads was carried out with the finite element technique, using ABAQUS software, which is widely used in simulating experimental circumstances in numerical studies. It has been reported that buildings in areas damaged by earthquakes are generally constructed using low-strength concrete and inadequate reinforcement. Additionally, construction errors also contribute to reducing the load-bearing capacity of structural elements. For this purpose, nine rectangular cross-section RC beams were experimentally constructed using low-strength concrete and inadequate bending and shear reinforcement. These beams were strengthened by wrapping them in different configurations with Carbon and Glass FRP (CFRP and GFRP) composites to resist shear and bending forces in both transverse and longitudinal directions, and their load-displacement curves were obtained. Subsequently, a three-dimensional Finite Element Model (FEM) was created to validate the experimental results. The FEM validation demonstrated high accuracy in replicating experimental outcomes, emphasizing the influence of mesh size, dilation angle, and concrete constitutive models on simulation fidelity. Parametric studies revealed that increasing longitudinal reinforcement diameters had minimal effect on load capacity but highlighted the critical role of transverse reinforcement, as reducing stirrup spacing significantly improved load-bearing capacity. GFRP-reinforced beams exhibited superior ductility and a 15% higher strength compared to CFRP, suggesting their suitability for applications demanding enhanced displacement capacity. Furthermore, the findings underline the need for refined FEM models to better capture inclined fiber orientations and optimize structural reinforcement strategies.

Abstract Background Glass fiber-reinforced polymer (GFRP) bars offer a superior alternative to steel bars in concrete reinforcement but are associated with wider cracks and higher deformation rates. This study introduces a novel approach by combining steel fibers (SFs) and carbon nanotubes (CNTs) to address these drawbacks and enhance the performance of GFRP-reinforced concrete beams. The unique contribution of this study lies in the simultaneous use of SFs and CNTs, which has not been extensively investigated, particularly in the context of GFRP-reinforced concrete. The study involved testing three sets of nine specimens with different concrete mixtures and reinforcement forms. Results The results showed that adding 0.04% CNTs by cement weight and 0.6% SFs by volume fraction significantly improved the mechanical performance of GFRP and steel reinforced beams. GFRP reinforced beams with CNTs and SFs exhibited a reduction in crack width, a 20% increase in load-carrying capacity, and a 25% reduction in deflection compared to reference specimens. Scanning electron microscope analysis further revealed that CNTs effectively enhanced tensile load transfer, improving flexural behavior of the beams. The finite element analysis using ANSYS confirmed the experimental findings, highlighting the improved stress distribution in the modified concrete mixtures. Conclusions Incorporating SFs and CNTs in concrete significantly improves the mechanical performance of GFRP-reinforced beams, making them more durable and resilient. These findings suggest that the proposed approach can enhance the longevity and sustainability of concrete structures, particularly in dynamic load applications such as bridges and high-rise buildings. Further experimental and analytical studies are recommended to assess the practical implications and cost-effectiveness of these materials in large-scale construction projects.

In this research, the effects of imbedding steel wires into the polyurethane foam of GFRP/Foam sandwich panel under three-point bending has been investigated. For this reason, three samples of non-reinforced, reinforced with two wires above and below and reinforced with three wires above and below the foam inside the GFRP sandwich panel were manufactured by vacuum bagging and tested under three-point bending in order to measure the specific strength of each sample. Moreover, a finite element model (FEM) was utilized using the Abaqus/Explicit package to further observe and analyze the stresses inside the samples. The results showed that imbedding steel wire inside the foam of the GFRP sandwich panel increased the bending strength by 25.2% in the two wire and 56.75% in the three-wire sample and bending modulus by 51.8% in two and 86% in three wire sample respectively. Since the weight of the wires with respect to the whole structure in negligible, the specific bending modulus of the sandwich panel was also improved by 21% in two and 44.8% in the three-wire sample. Finally, the results obtained from the experiments showed to have a decent agreement with the simulated model.

Wood is a heterogeneous and anisotropic material, and its mechanical properties are different from other building materials. It is necessary to know the mechanical properties of wood materials in buildings, such as carriers, floor beams, roof timber, plywood roof covers, laminated beams, stair or wire poles, yacht poles, and furniture frames. Tensile strength is the resistance of wood material to two forces applied in opposite directions, trying to break and separate the fibers. This study aimed to determine the tension strength perpendicular to fibers of beech timber reinforced with basalt fiber-reinforced polymer (BFRP), glass fiber-reinforced polymer (GFRP), and plaster mesh (PSM). One component polyurethane (PUR-D4) and polyvinyl acetate (PVAc-D4) were used as the adhesive. The BFRP, GFRP, and PSM were added as one layer of reinforced materials. Experimental materials reinforced with BFRP, GFRP, and PSM were tested in the unreinforced locations, of reinforced lumber with BFRP, GFRP, and PSM. Tests were performed to investigate the tensile strength perpendicular to fiber (┴σt). The test results showed that the reinforcement process increased the (┴σ). The ┴σt value of samples reinforced with BFRP was 13%, 32%, and 66% higher than those reinforced with GFRP, unreinforced, and reinforced PSM, respectively. Accordingly, the BFRP shows potential to serve as an option for reinforced wood structural members.

Trends in the automotive industry are changing rapidly due to environmental factors, including climate change-induced exhaust gas regulations, urban traffic congestion, and the merging of communication and mobility technologies. As a result, new technologies such as electrification, autonomous driving, and mobility as a service (MaaS) are emerging, leading to the development of various types of mobility solutions, including battery electric and hydrogen vehicles, advanced air mobility (AAM), and purpose built vehicle (PBV). In response to these developments, research on a wide range of lightweight materials is being conducted to meet the requirements of these various modes of transportation. Carbon fiber-reinforced plastic (CFRP) is the most effective lightweight material for weight reduction; however, its high cost limits its application. To overcome this limitation, one solution is to produce composite materials using lower cost alternative materials and mass production processes. Another approach is to develop lightweight composite materials that offer additional advantages. Nevertheless, in mobility modes such as AAM, weight reduction is far more critical than cost sensitivity, indicating a potential increase in composite part application in this field. [ABSTRACT FROM AUTHOR]

A full-scale deck slab (15,240 mm × 3,890 mm × 210 mm) supported by steel girders spaced at 3.05 m, including a 3,810 mm × 3,890 mm section incorporating a new design of glass fiber–reinforced polymer (GFRP) stay-in-place (SIP) structural form, is tested under 3M rolling load cycles. The SIP form comprises transverse GFRP I-beams spanning the steel girders and GFRP ribbed plates (planks) spanning the transverse GFRP I-beams and supported by their lower flanges. The design of the SIP form was governed by readily available pultruded sections such that they meet deflection limits under self-weight of fresh concrete and also provide reinforcement ratios comparable to, or exceeding, the Canadian Highway Bridge Design Code (CHBDC) requirements for GFRP rebar. This deck section is compared with another section designed according to CHBDC with top and bottom GFRP rebar meshes. The deck was tested using the 250 kN Rolling Load Simulator (ROLLS) at Queen's University, Canada, which is equipped with two half-axles spaced at 1.2 m, each comprising nitrogen-inflated dual tires. After 3M cycles, the section with SIP structural form showed very similar performance to that of the GFRP rebar section with the stiffness reducing by 72% in both. Nearly 90% of stiffness reduction occurred in the first 0.4M cycles. The residual deflection of the SIP form section was only 60% of that of the rebar section at 3M cycles. Live load deflection ratio reached 3.4 at 3M cycles, almost identical to the rebar section. The span/800 deflection limit was reached at 0.8M cycles, compared with 1.1M cycles for the rebar section. The maximum tensile strain reached in the GFRP SIP form system after 3M cycles was only 11% of its ultimate value. Practical Applications: The use of glass fiber–reinforced polymer material as reinforcement for bridge decks has been well investigated. Researchers have also investigated the applicability of a reinforcement design concept, stay-in-place (SIP) form, which acts as both formwork for casting concrete and permanent reinforcement. This paper investigates the rolling load fatigue performance of a full-scale GFRP SIP form reinforced bridge deck. The GFRP SIP form system featured in this study is made from an off-the-shelf product. The experiment simulated actual traffic load with air-inflated rubber tires for 3 million cycles and the bridge deck exhibited adequate performance. [ABSTRACT FROM AUTHOR]

Concrete columns with hollow-core sections find widespread application owing to their excellent structural efficiency and efficient material utilization. However, corrosion poses a challenge in concrete buildings with steel reinforcement. This paper explores the possibility of using glass fiber-reinforced polymer (GFRP) reinforcement as a non-corrosive and economically viable substitute for steel reinforcement in short square hollow concrete columns. Twelve hollow short columns were meticulously prepared in the laboratory experiments and subjected to pure axial compressive loads until failure. All columns featured a hollow square section with exterior dimensions of (180 × 180) mm and 900 mm height. The columns were categorized into four separate groups with different variables: steel and GFRP longitudinal reinforcement ratio, hollow ratio, spacing between ties, and reinforcement type. The experimental findings point to the compressive participation of longitudinal GFRP bars, estimated to be approximately 35% of the tensile strength of GFRP bars. Notably, increasing GFRP longitudinal reinforcement significantly improved the ultimate load capability of hollow square GFRP column specimens. Specifically, elevating the ratio of GFRP reinforcement from 1.46% to 2.9%, 3.29%, 4.9%, and 5.85% resulted in axial load capacity improvements of 32.3%, 43.9%, 60.5%, and 71.7%, respectively. Specifically, the GFRP specimens showed a decrease in capacity of 13.1%, 9.2%, and 9.4%, respectively. Notably, the load contribution of steel reinforcement to GFRP reinforcement (with similar sectional areas) was from approximately three to four times the axial peak load, highlighting the greater load participation of steel reinforcement due to its higher elastic modulus. In addition, the numerical modeling and analysis conducted using ABAQUS/CAE 2019 software exhibited strong concordance with experimental findings concerning failure modes and capacity to carry axial loads.

In this research, rice husk ash (RHA) and eggshell ash (EGA) were used as biogenic materials for total replacement of pure quartz (SiO2) and calcium oxide (CaO) respectively in the traditional 45S5 bioactive glass composition by powder metallurgy route. Body formulation with nominal composition 45% RHA (SiO2), 24.5 EGA (CaO), 24.5% Na2O and 6% P2O5 was composed. The batch material was properly mixed with addition of 2% PVA (Polyvinyl alcohol) as binder and compacted at 70 MPa to produce compact samples of 40 x 20 mm. The samples were then allowed to dry in an ambient temperature followed by sintering at 1000°C for 2 h, then allowed to cool to room temperature. Selected samples were immersed inside prepared simulated body fluid (SBF – pH 7.4) at 37 °C for 5, 9, and 18h respectively. Physical, microstructure and phase evaluation were conducted to examine the developed bio-ceramic. The results showed the bio-waste based 45S5 bioceramic has bulk density and porosity of 1.02 g/cm3 and 62% respectively while deposits of carbonate-hydroxyapatite were found to increase with immersion period showing good bioactivity and affirm that the developed bio-waste based bioceramics are bioactive and can find suitable application bone repair.

Abstract This article investigates the behavior of hybrid FRP Concrete-Steel columns with an elliptical cross section. The investigation was carried out by gathering information through literature and conducting a parametric study, which resulted in 116 data points. Moreover, multiple machine learning predictive models were developed to accurately estimate the confined ultimate strain and the ultimate load of confined concrete at the rupture of FRP tube. Decision Tree (DT), Random Forest (RF), Adaptive Boosting (ADAB), Categorical Boosting (CATB), and eXtreme Gradient Boosting (XGB) machine learning techniques were utilized for the proposed models. Finally, these models were visually and quantitatively verified and evaluated. It was concluded that the CATB and XGB are standout models, offering high accuracy and strong generalization capabilities. The CATB model is slightly superior due to its consistently lower error rates during testing, indicating it is the best model for this dataset when considering both accuracy and robustness against overfitting.

The automobile industry is exploring the use of HP-RTM (high-pressure resin transfer molding) for mass-producing glass fiber-reinforced plastic (GFRP) chassis parts to achieve weight reduction. In this process, dry fabric is used as a material. However, the fatigue endurance performance of these parts deteriorates due to the bobbin threads in the dry fabric. This study aims to propose a laminating method to prevent the deterioration of the durability of GFRP chassis parts with bobbin threads. Specimens were fabricated with different fiber volume fractions (Vf) and bobbin thread positions. After manufacturing, static properties were evaluated to compare the physical properties of each specimen, and the stress for fatigue durability evaluation was determined based on these static properties. Finally, fatigue endurance performance evaluations were conducted to determine the optimal lamination conditions for GFRP chassis parts. The results showed that for the three laminating methods applied in this study, an increase in Vf not only enhanced the static properties but also reduced waviness, as confirmed through OM images and changes in the slope of the stress–strain curve. Additionally, fatigue endurance tests revealed that, along with the improvement in waviness, adjusting the position of the bobbin threads—which negatively impact durability—resulted in an increase in fatigue endurance performance from approximately 67,000 cycles to about 870,000 cycles, an improvement of approximately twelve times. [ABSTRACT FROM AUTHOR]

The compressive strength of composite materials is critical for designers. This study investigates how seawater immersion influences the mechanical properties and compressive behaviour of solid and open-hole glass/epoxy laminates used in aircraft structures. The specimens were divided into three groups: first not immersed, second immersed in seawater for 30 days, and last sun-dried 12 hours after immersion. Immersion in seawater lowered the compressive strength of solid and open-hole specimens by 40 % and 33 %, respectively. The sun-drying process after seawater immersion increased the compressive strength of solid and open-hole specimens by 5 % and 17 %. After drying, the residual strength of solid and open-hole GFRP was 65 % and 84 %, respectively. In solid GFRP composites, the seawater immersion and drying process is irreversible; besides, in open-hole composites it can be reversible. The compressive examination was numerically duplicated using a finite element method (FEM) model of the composite material. [ABSTRACT FROM AUTHOR]

The behaviour of lightweight concrete (LWC) edge column-slab connections reinforced with two types of flexural reinforcement glass fiber-reinforced polymer (GFRP) and steel bars with different ratios of shear reinforcement are investigated experimentally and analytically using ABAQUS software. The experimental protocol covered evaluation of eight slabs and edge columns measuring subjected to static loading. Slabs are evaluated as supported, free-standing at one edge, and the column connection is included. The slabs are divided into two groupings, with four slabs in each group. The first group was reinforced with steel flexural, while the second group was reinforced with GFRP reinforcement. Within each group, one slab lacked shear reinforcement, while the other was reinforced with a varying shear reinforcement ratio. A good agreement was found between the numerical FE model and experimental outcomes in most tested slabs. [ABSTRACT FROM AUTHOR]

A novel non-destructive testing scheme was proposed for the detection of impact damage in glass fibre-reinforced polymer (GFRP) composites using a microwave planar resonator sensor. The sensor offers the advantages of small size, low cost and simple structure. It is an open-circuited λ/2 long microstrip line and the detection principle is material perturbation. Electromagnetic simulation verifies the sensor design. A GFRP specimen subjected to 5,10 and 20 J impact was examined. The 20 J impact damage was detected through line and two-dimensional scanning. The line scanning enabled accurate localisation of the damage, whereas the two-dimensional scanning facilitated more precise reconstruction of the surface damage features in addition to localisation. The sensor performance for detecting impact damage with lower energy levels was investigated by line scanning. It was found that the sensor could detect and locate 10 J impact damage. Principal component analysis was introduced to significantly reduce the false detection of the 5 J impact damage. It is well demonstrated that the proposed scheme could serve as an alternative method. [ABSTRACT FROM AUTHOR]