Composite Bars Research Articles

Application of Composite Bars in Wooden, Full-Scale, Innovative Engineering Products-Experimental and Numerical Study.

The commercialization of modular timber products as cost-effective and lightweight components has resulted in innovative engineering products, e.g., glued laminated timber, laminated veneer lumber, I-beams, cross-laminated timber and solid timber joined with wedge joints. With the passage of time, timber structures can deteriorate, or new structural elements are required to increase the stiffness or load-bearing capacity in newly built structures, e.g., lintels over large-scale glazing or garages, or to reduce cross-sectional dimensions or save costly timber material while still achieving low weight. It is in such cases that repair or correct reinforcement is required. In this experimental and numerical study, the static performance of flexural timber beams reinforced with prestressed basalt BFRP, glass GFRP and hybrid glass-basalt fiber bars is shown. The experimental tests resulted in an increase in the load-carrying capacity of BFRP (44%), GFRP (33%) and hybrid bars (43%) and an increase in the stiffness of BFRP (28%), GFRP (24%) and hybrid bars (25%). In addition to this, glued laminated timber beams reinforced with prestressed basalt rods subjected to biological degradation, 7 years of weathering and prolonged exposure to various environmental conditions were examined, and an increase in the load-bearing capacity of 27% and an increase in stiffness of 28% were obtained. In addition, full-size laminated timber beams reinforced with prestressed basalt bars were investigated in the field as an exploratory test under fire conditions at elevated temperatures, and the effect of the physical-mechanical properties during the fire was examined via an analysis of these properties after the fire. In addition, a satisfactory correlation of the numerical simulations with the experimental studies was obtained. The differences were between 1.1% and 5.5%. The concordance was due to the fact that, in this study, the Young, Poisson and shear moduli were determined for all quality classes of sawn timber. Only a significant difference resulted in the numerical analysis for the beams exposed to fire under fire conditions. The experimental, theoretical and numerical analyses in this research were exploratory and will be expanded as directions for future research.

Flexural behavior of high strength concrete shallow wide beams reinforced by hybrid longitudinal reinforcement

ABSTRACT One of the most common statistical systems used in structures especially for wide span slabs are ribbed slabs with shallow wide beams (SWB). This experimental study aimed to investigate and enhance the flexural behavior of high-strength concrete SWB using hybrid longitudinal reinforcement from steel and advanced composite materials as a tensile main reinforcement in SWB. Longitudinal advanced composite bars locally manufactured from ribbed glass fiber reinforced polymer (GFRP) and the second type was ribbed basalt fiber reinforced polymer (BFRP). A group of six half scale SWB were examined in structures laboratory of American University in Cairo with dimensions 2.1 × 0.6 × 0.25 m for length (L), width (B) and depth (d) respectively with constant size effect (d/B). The first three specimens were completely reinforced at tension side with Steel, GFRP or BFRP ribbed bars to be considered a control specimen. Use of GFRP and BFRP bars enhanced the flexural capacity of SWB with 41% and 43% respectively compared to specimen completely reinforced with steel. But on the other hand, the crack propagation of specimens completely reinforced with GFRP and BFRP developed more quickly and had larger crack width compared to specimen completely reinforced with steel. Hybrid reinforcement from Steel with GFRP, Steel with BFRP and Steel with GFRP and BFRP specimens are used to enhance the crack pattern and mode of failure without a significant loss in flexural capacity of SWB. The flexural capacity of these three specimens was enhanced with 26%, 30% and 41% with a significant enhancement in crack pattern and ductility.

Bond behavior between bundled composite bars and concrete using beam-end pullout tests

Bundled reinforcement can improve construction efficiency by reducing the number of connectors required. The steel-fiber reinforced polymer (FRP) composite bar (SFCB) is a novel reinforcement with high strength, moderate modulus of elasticity and good durability. Four groups of pullout tests were carried out, with parameters including the number of bars within each bundle, bonded length, and rebar type (steel bar, BFRP bar, SFCB). The failure modes of bar pullout without or after yielding, rebar fracture, and concrete splitting were observed. Compared to the single-bar specimen, the two-bar and three-bar bundled specimens resulted in approximately 30% and 40% decrease in average bond strength. The yielding slip sy of the three-bar bundled SFCB specimen is 3.8 times that of the single-bar specimen, indicating that bundled reinforcement can effectively control sy. A simplified bond strength prediction method and a bond stress-slip constitutive model based on the equivalent effective area approach are proposed. Finite element (FE) models were established and verified, and the failure modes of bar fracture are obtained by varying the bonded lengths for different bundled reinforcements, the ultimate slip of four-bar bundled BFRP bars increased by 127%. Recommendations for the development length of bundled SFCBs are proposed based on the FE results, which provide enough safety redundancy.

Experimental study and prediction on tensile behavior of steel fiber-reinforced-carbon/glass hybrid composite bars in concrete environment

The tensile behavior of steel fiber-reinforced-carbon/glass hybrid composite bars (S-CG HCBs) in concrete environment was experimentally investigated. The influences of the steel fiber content (VS) and the carbon-glass ratio (VC/VG) on the tensile behavior of corroded S-CG HCBs were analyzed. The optical microscope (OM) was used to reveal the morphology and corrosion mechanism of S-CG HCBs. The results show that under tensile load, S-CG HCBs exhibited a pseudo-yield platform due to the separate fracture of the three types of fibers and the buckling of steel fibers. The retentions of yield and ultimate strengths of the S-CG HCBs in alkaline solution increased with the VS or VC/VG increased due to the reduction of glass fiber content and its more inferior alkali resistance than carbon and steel fibers. After 63 days of corrosion at a 40 ℃, the specimen (S30C1G6), whose VS and VC/VG are 30% and 1/6, respectively, exhibited the highest tensile strength retention rate of 87.88% compared to other specimens. In addition, the tensile stress retention of S-CG HCBs serviced in concrete environment under various ambient temperatures was predicted based on the Arrhenius equation.

Effectiveness of FRP bar anchors for prestressed concrete members

Prestressed concrete members are widely used around the world to realize different types of structure, including bridges and skyscrapers. Steel strands are generally employed to apply a compression force into the concrete. Recently, fiber-reinforced polymer (FRP) composite bars have been considered for replacing traditional steel strands in specific applications. The main advantage of FRP bars is their resistance to corrosion. Furthermore, they may have a higher tensile strength-to-weight ratio and fatigue resistance compared to steel strands. Although using prestressed FRP bars may entail for advantages over traditional steel solutions, the anchorage system is an open issue for this technology. Indeed, the anchorage should guarantee a high level of tensile stress into the bar and, at the same time, avoid local failures.In this paper, the preliminary results of an experimental campaign comprising tensile tests of glass and carbon FRP bars with different anchors are provided and discussed. The experimental campaign was aimed at investigating the effectiveness of newly developed wedges in properly anchoring the composite bars. Tensile test results and modes of failure are discussed, shedding light on the main parameters that affect the mechanical behavior of the bars considered.

Utilization of milk powders and protein concentrates in the formulation of novel composite cereal-based functional energy bars

Utilization of milk powders and protein concentrates in the formulation of novel composite cereal-based functional energy bars

Research on the bonding performance of TRC composite embedded CFRP bars and the flexural performance of reinforced beams

To improve the flexural performance of beams and compensate for the shortcomings of single reinforcement, this paper proposed a reinforcement method of TRC compound prestressed NSM-CFRP bars. The direct pull-out tests of 21 pull-out specimens and four point bending tests of six beams were carried out, and the effects of the CFRP bar diameter, slot size and bond length on the bonding performance of TRC compound embedded CFRP bars and the effects of the number of TRC layers and slot spacing on the flexural performance of the composite reinforced beams were investigated. The results show that the pull-out specimens have four damage modes: slip damage at the CFRP bar/structural adhesive interface, slip damage at the structural adhesive/concrete interface, splitting failure at the adhesive layer and concrete cracking failure around the slot, which are affected by the slot size, bar diameter and bond length. The average bonding stress and drawing load can be increased with increasing slot size. The drawing load increases with increase in the diameter and bonding length of the CFRP bars, but the average bonding stress decreases due to the uneven stress distribution. An appropriate increase in the number of TRC layers can increase the ultimate load and stiffness of the reinforced beam to a certain extent and reduce the maximum crack width, but too many layers of TRC reinforcement will be more likely to peel off and stop functioning, resulting in a reduction of the load carrying capacity. The slot spacing has no evident effect on the stiffness, bearing capacity and maximum crack width of the beam, but the narrow slot edge spacing will lead to the concrete tensile crack failure at the end of the beam, which is brittle, and can be avoided by reinforcing the ends, The bond-slip model for composite reinforced specimens was derived by fitting the bond-slip equation proposed by Cruz and Barro. Based on the maximum crack width calculation equation for reinforced concrete beams in the code, the maximum crack width calculation equation for composite reinforced beams under normal service limit load is proposed, and the differences between the theoretical and empirically obtained values are found to be small, indicating the good applicability of the calculation model.

Durability of glass fiber reinforced thermoplastic polypropylene composite bars under the coupling effect of seawater and sea sand concrete environment and sustained bending

AbstractThe long‐term interfacial shear strength (IFSS) and flexural strength of GFPP bars under the coupling effect of bending and immersion in the simulated seawater and sea sand concrete (SWSC) solution were studied by an acceleration experiment. Three temperatures and three bending stress levels (0%, 9.8%, and 29.4% of the maximum flexural strain of GFPP bars) were used to accelerate the experiment. Results indicate that the degradation of mechanical properties of GFPP bars is relatively sensitive to the immersion temperature. Low bending stress did not accelerate the degradation of GFPP bars compared with unbent GFPP bars while high bending stress dramatically accelerated the degradation. Microscopic tests found there is corrosion of glass fibers and debonding between glass fibers and polypropylene but no obvious chain breaks of polypropylene occurred. Based on the Arrhenius theory, long‐term stable retention rates of the IFSS of GFPP bars with zero and low bending stress immersed in the simulated SWSC solution are 42.4% and 52.3%.Highlights Low‐stressed GFPP bars degraded similarly or even slower than unbent GFPP bars. GFPP bars degraded mainly due to interfacial debonding and fiber corrosion. Long‐term IFSS of GFPP bars under a coupling effect was predicted.

Lateral impact performances of geopolymer concrete columns reinforced with steel-BFRP composite bars

There is a growing public interest in exploring materials that can enhance the sustainability and durability of conventional steel reinforced concrete (RC) structures, such as geopolymer concrete (GPC) and steel-fibre reinforced polymer composite bars (SFCBs). GPC is produced with industrial waste such as fly ash and slag to replace ordinary Portland cement concrete (OPC), and SFCB is a new reinforcement bar with a layer of fibre reinforced polymer (FRP) enclosing a steel inner core to protect it from corrosion. No studies have ever been reported on the impact-resistant performances of GPC or fibre-reinforced GPC (FRGPC) columns reinforced with SFCBs subjected to vehicle or ship impacts. In this study, GPC/FRGPC columns reinforced with steel-basalt FRP composite bars (SBCBs) were prepared and tested by a pendulum impact testing system. Their impact-resistant performances were compared. It was found that the columns experienced similar damage modes regardless of reinforcement type and fibre content. The addition of hybrid carbon fibres (CFs) and basalt macro fibres (BMFs) could effectively reduce cracking damage and mid height deflections of columns. As compared to steel bar reinforcements, SBCB reinforcements led to similar impact force and maximum mid height deflections, but could reduce the residual mid height deflections of the columns by 7–42% under the impact velocity of 2.64–3.49 m/s, indicating SBCBs have great potential to replace steel bars in constructing more sustainable and durable concrete structures.

A magnetic stir bar sorbent of metal organic frameworks, carbon foam decorated zinc oxide and cryogel to enrich and extract parabens and bisphenols from food samples

A porous composite magnetic stir bar adsorbent was fabricated for the extraction and enrichment of parabens and bisphenols from selected beverage samples. The adsorbent comprised a metal organic framework, carbon foam decorated zinc oxide and magnetic nanoparticles embedded in polyvinyl alcohol cryogel. The porous composite stir bar adsorbent could adsorb parabens and bisphenols via hydrogen bonding, π-π and hydrophobic interactions. In the best conditions, linearity was good from 5.0 to 200.0 µg/L for methyl paraben, ethyl paraben and bisphenol A and from 10.0 to 200.0 µg/L for bisphenol B and butyl paraben. Limits of detection ranged from 1.5 to 3.0 µg/L. The developed composite stir bar was successfully applied to extract and determine parabens and bisphenols in fruit juice, beer and milk. Recoveries ranged from 89.5 to 99.5 % with RSDs lower than 6 %. The developed sorbent and new methodology were evaluated in terms of its green character with satisfactory results.

Bond behavior between steel-FRP composite bars and engineered cementitious composites in pullout conditions

Steel-FRP composite bar (SFCB) reinforced engineered cementitious composites (ECC) members are promising to apply in structural engineering due to their excellent mechanical properties and durability. The bond behavior between SFCB and ECC was investigated by direct pullout tests. The experimental variables included the diameter of SFCB, bond length, type of matrix, compressive and tensile strengths of ECC, and type of reinforcement. All ECC specimens failed in a ductile manner with ECC keys being crushed and sheared off. The bond strength and bond toughness of ECC specimens were higher than those of concrete specimens possessing similar compressive strengths. An interfacial bond-slip model was proposed to predict the bond behavior of SFCB embedded in ECC. An iteration procedure was performed utilizing the developed bond-slip model to analyze the distributions of bond stresses and slips. Notably, an increase in bond length and the yielding of SFCB led to heightened non-uniformity in bond stress and slip distributions. Furthermore, equations were derived to predict the embedment lengths of SFCB applicable to various scenarios.

An investigation of fatigue behavior and residual strength model of steel-GFRP composite bar

Steel-fiber reinforced polymer (FRP) composite bar (SFCB) combines the advantages of corrosion resistance of FRP and good ductility of steel, and is a promising reinforcement material to improve the service life of marine structures. However, the fatigue behavior of SFCB is complex and has not been explored. Therefore, in this study, fatigue tests were conducted at different stress levels (0.32, 0.36, and 0.41 of quasi-static tensile strength with a fixed stress ratio of 0.1) and tensile tests were performed after fatigue pre-damage for a certain number of cycles (25%, 50%, and 75% of the fatigue life) to investigate the fatigue behavior of SFCB. The results show that fatigue failure is caused by steel core fracture, and the FRP layer can improve the fatigue life. Compared with the change of residual strength, the stiffness degradation of SFCB during fatigue loading was not significant. Finally, a residual strength prediction model containing known parameters of the S-N curve is also proposed, which can well predict the residual strength decay of SFCB after fatigue damage. In conclusion, these findings and the proposed residual strength prediction model contribute to the understanding and design of SFCBs.

A surrogate model for finite element simulation of elastic wave propagation in composite materials

Deep learning surrogate models can be employed in solid mechanics to forecast the behavior of structures subjected to various loading conditions, substantially decreasing the computational costs associated with simulations. In this letter, we have utilized convolutional neural networks and Fourier transform to predict the elastic wave output from composite bars. The microstructures of the bar are utilized as inputs to the deep learning model, while the output is the elastic wave response. The convolutional neural network learns to identify crucial input composite features and utilizes this information to predict the output elastic waves. Finally, the mean squared error of the predicted output signals is compared to the actual output signals, which was used to evaluate the model. The outcomes of this study demonstrate that the deep learning model can precisely and swiftly predict the output elastic waves of the composites, thus serving as a surrogate model for time-consuming finite element simulations.

Assessment of Composite Bars and FRP Panels for Seismic Bridge Decks

Seismic Strengthening offers a cost-effective and sustainable solution for constructing bridges in seismic zones. In these rehabilitation interventions, Fiber Reinforced Polymer (FRP) composites are often used instead of steel members due to their lightweight nature, high strength, and excellent corrosion resistance. Researchers are now focusing on creating innovative FRP-concrete hybrid structures. This study specifically investigates the numerical modeling of the response of a hybrid FRP-concrete jacket bridge pier subjected to quasi-static tests. The Finite Element Method (FEM) results demonstrated a significant correlation with the experimental response, particularly in terms of the load-displacement curve failure mode. Once the model was validated, various alternative designs were numerically tested to evaluate the impact of each model on the load-bearing capacity. These designs included altering the height of the CFRP sheet, adjusting the height and congestion of the CFRP bar, and comparing the performance of the concrete jacket with and without the CFRP sheet. After reinforcing the CFRP sheets and incorporating Near-Surface-Mounted (NSM)-CFRP bars, the reinforcement system, along with the new concrete jacket, effectively transferred the integrity of the broken pier area and maintained a constant load-bearing capacity for the bridge pier. However, when the CFRP sheet was added to the aforementioned system, the load capacity of the bridge pier increased by more than 60%. Therefore, it can be concluded that seismic enhancement techniques utilizing CFRP sheets and mounted NSM-CFRP bars are successful in enhancing the strength and resilience of the concrete bridge pier.

Sub-zero temperature flexural and flexural fatigue behaviour of glass fabric /epoxy composite tubular anti roll bars

Flexural and flexural fatigue reliability of glass fabric/epoxy composites used in anti-roll bars in room and sub-zero temperature regions at +25 °C, +10 °C, 0 °C, −10 °C, −20 °C, −30 °C, and −40 °C are investigated. The mean flexural strength of anti-roll bars substantially varies and improves in the sub-zero flexural property assessment (+25 °C to −40 °C). The fixed amplitude pulsating mode fatigue test was carried out at temperature points, i.e., 25 °C and −40 °C. The improvement in fatigue strength was observed 3.5 times at a sub-zero temperature of −40 °C. The fatigue durability of glass/epoxy composite anti-roll bars is observed to be longer at sub-zero temperatures due to residual stresses building up, an increase in glass transition temperature, and a lack of molecular mobility leading to higher chain stiffness in the epoxy matrix. The structural properties like flexural rigidity and modulus were calculated with reference to the shape factor and test temperatures for better correlations. These lifetime prediction studies under unpredictable operating conditions for automotive are crucial in the development of robust designs. Automotive performance under service conditions and environmental extremes will become increasingly important as lighter weight, longer life, and higher structural performance continue to evolve.

Investigation of chatter suppression by using rotating composite boring bar CNT-filled based on a modified nonlinear dynamical model

Investigation of chatter suppression by using rotating composite boring bar CNT-filled based on a modified nonlinear dynamical model

Compressive Performance of Longitudinal Steel-FRP Composite Bars in Concrete Cylinders Confined by Different Type of FRP Composites.

This paper presents an experimental study on the compressive performance of longitudinal steel-fiber-reinforced polymer composite bars (SFCBs) in concrete cylinders confined by different type of fiber-reinforced polymer (FRP) composites. Three types of concrete cylinders reinforced with (or without) longitudinal SFCBs and different transverse FRP confinements were tested under monotonic compression. The results showed that the post-yield stiffness of SFCBs is higher when confined with high elastic modulus carbon fiber-reinforced polymer (CFRP) composite than with low elastic modulus basalt fiber-reinforced polymer (BFRP) composite. Decreasing confinement spacing did not significantly improve the compressive strength of SFCBs in concrete cylinders. The compressive failure strain of SFCBs could possibly reach 88% of its tensile peak strain in concrete cylinders confined by CFRP sheets, which is significantly higher than the value (around 50%) in previous studies. Existing design equations, which applied a strength reduction factor or a maximum compressive strain of concrete to consider the compressive contributions of SFCBs in concrete members, underestimate the load-carrying capacity of SFCB-reinforced concrete cylinders. The design equation that considers the actual compressive stress of SFCBs gives the most accurate prediction; however, its applicability and accuracy need to be verified with more experimental data.

Long‐term residual properties and durability of glass fiber reinforced polymer composite exposed to alkaline solution and natural weather for a decade

AbstractThis paper presents a comprehensive analysis of the residual thermal and mechanical properties of pultruded glass fiber reinforced polymer composite bars following a decade of conditioning in an alkaline solution and exposure to natural weather conditions. The study focuses on evaluating the changes in the glass transition temperature (Tg) of the polymer matrix and its impact on the bar's mechanical performance. The results indicate that the Tg retained approximately 94.7% of its initial value, with the decrease attributed to the plasticizing effect of absorbed water. The flexural modulus, flexural strength, and transverse shear strength were found to retain 91.8%, 77.2%, and 97.3% of their original values, respectively. The reductions in strength and stiffness were primarily attributed to a weakening in the bonding between the fibers and the polymer matrix. Fractographic analysis revealed that the failure of the plasticized and softened polymer matrix contributed to the observed reductions in strength. Interestingly, the short beam shear strength remained relatively unchanged, as the diffusion of water into the core of the bars at ambient temperatures had a minimal effect. This slower water diffusion in the core led to insignificant degradation of the short beam shear strength.Highlights GFRP bars were exposed to alkaline solution and natural weather for a decade. The water diffusion was a key factor in determining the residual properties of the GFRP bars. The absorbed water plasticises the polymer matrix in GFRP bars. The mechanical property losses in GFRP bars were associated with changes in the matrix property.

Deterioration of basalt-based reinforcement in corrosive environments: experimental monitoring and mathematical models

The basalt-based reinforcing elements are considered as alternative to conventional steel-based reinforcing elements (rebars, wires). The motivation to use basalt-based elements (fibers, composite bars, meshes etc.) is better corrosion resistance of basalt fibers especially in sea-water environment, compared to carbon steel. Nevertheless, it does not mean that basalt fibers are 100% corrosion resistant. The basalt fibers are produced from silicate melt of proper composition, i.e. the basalt fibers are vulnerable to both acid and alkaline hydrolysis, as well as other silicates do. When basalt fibers are used as reinforcement in concrete, the alkaline hydrolysis will become an important issue. The present paper deals with experimental observation of basalt fibers in alkaline environment of Simulated Pore Solution. The fibers deterioration was monitored by their mass loss and SEM microscopy. Jander’s model was used to describe mathematically the kinetics of the fibers alkaline hydrolysis. The results revealed that a corrosion products layer is formed on the fibers surface in this environment. The composition of this layer corresponds to N-A-S-H and C-A-S-H phases known from alkali-activated aluminosilicates or hydrated Portland cement.

Investigation on bond behavior of steel-FRP composite bars in engineered cementitious composites by spliced beam tests

The collaborative utilization of steel-FRP composite bar (SFCB) and engineered cementitious composites (ECC) represents a favorable choice for engineering structures exposed to aggressive environments, offering benefits involving both mechanical behavior and durability. This paper primarily studies the bond performance of SFCB embedded in ECC through spliced beam tests coupled with finite element analysis. The findings demonstrate that with an appropriate cover thickness or transverse confinement, spliced ECC beams exhibit failure modes characterized by splitting and pull-out. Under such conditions, the bond-slip response demonstrates limited sensitivity to changes in cover thickness and transverse confinement. Conversely, increasing the cover thickness or introducing transverse confinement in spliced concrete beams, which exhibit splitting failure, significantly enhances the bond strength. Furthermore, in contrast to spliced concrete beams, spliced ECC beams are observed to demonstrate a bond toughness that is 3.85–12.10 times greater. The discrepancy in bond toughness between ECC and concrete diminishes as the cover thickness and transverse confinement increase. Notably, the uniform distribution of bond stress in the splice region of ECC beams remains unaffected by variations in splice length. To incorporate the impact of bond stress distribution when calculating the splice length of SFCB in ECC beams, a coefficient of 0.85 is introduced.