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Abstract Pultruded glass fiber reinforced polymer (GFRP) sections face a critical issue of premature web crippling failure when loaded in the transverse direction. However, limited research on the web crippling behavior of asymmetric sections like channel section was reported in the literature. In addition, the effect of specimen length on the web crippling behavior has not been explicitly investigated. This paper presents an experimental study on the web crippling behavior of pultruded GFRP channel sections under transverse bearing load. Four channel sections with various dimensions were tested under two transverse loading conditions, i.e. interior-two-flange (ITF) and exterior-two-flange (ETF). For each section, two specimen lengths were adopted to study the effect of specimen length on the web crippling behavior. Therefore, three variables including sectional dimensions, specimen length and loading conditions were considered in the experimental program. Two failure modes, namely web-flange junction failure and web buckling failure, were observed. The load-displacement curves and web crippling capacities of all specimens were reported and compared. Finally, design equations were proposed considering the failure mechanisms. The predicted web crippling capacities generally agreed well with the experimental results. [ABSTRACT FROM AUTHOR]

Abstract The present study presents an experimental investigation into the real-time monitoring of the drilling process of Glass Fiber Reinforced Polymer (GFRP) composite with Carbon Nanotubes (CNTs) buckypaper sensor. The spray-vacuum filtration method was employed to synthesize CNTs buckypaper sensor and then embedded into the GFRP to serve two purposes namely interlaminar enhancement and sensor monitoring the drilling process of the GFRP. Both modes I and II interlaminar fracture toughness tests were conducted to ascertain the enhancement ability of the buckypaper. Considerable improvements in both modes of fracture toughness were recorded in the specimens with CNTs buckypaper interlayer. For the CNTs buckypaper acting as a sensor, drilling experiments were carried out on the GFRP where real-time information of the drilling process particularly the drilling tool position could be predicted. This can be crucial in cases where drilling parameters like the feed rate have to be changed at a certain drilling depth in order to reduce or eliminate the exit delamination. The Scanning Electron Microscope (SEM) was finally employed to study the enhancement ability of the CNTs buckypaper and the microstructure of the drilled holes. The current work has substantiated the possibility of using CNT buckypaper both as an interlaminar enhancement and as a sensor to monitor the drilling process. [ABSTRACT FROM AUTHOR]

Abstract The effect of impact load with low velocity in thin-walled plates and profiles has been investigated. The paper deals with the relation between damage propagation, size and shape as a function of boundary conditions, layer arrangements and impact energy. The structures under consideration were made of eight-layer Glass Fiber Reinforced Polymer (GFRP) laminate with a quasi-isotropic, quasi-orthotropic and angle ply arrangement of layers. The standardised plates predefined to CAI tests and channel section profiles have been subjected to impact load. Based on the performed tests, the impact characteristics have been obtained and compared with the theoretical model (one degree of freedom mass-spring system). Further, despite it not being mentioned in the ASTM 7136 standard, characteristic curves were identified. It was noted that the impacts introducing matrix damages and the partial fracture of the fibres significantly change the course of the Force-Time histories, particularly after the maximum impact force is reached. [ABSTRACT FROM AUTHOR]

This study aims to improve the web crippling performance of pultruded glass fibre-reinforced polymer (GFRP) C sections using fibre-reinforced epoxy composite (FEC). The strengthened GFRP C sections were subjected to two loading conditions: interior-two-flange (ITF) and exterior two-flange (ETF). The parameters considered were bearing lengths, FEC strengthening length and thicknesses. Two failure modes, namely web-flange junction failure and web buckling failure were observed for the pultruded GFRP C sections under ETF loading conditions as the bearing length changed. While the combination of the web-flange junction and FEC crushing failures were observed under ITF loading conditions at 20 mm and 50 mm bearing lengths. Furthermore, the average web crippling capacity of strengthened GFRP C sections improved by up to 426 % and 488 %, in comparison to control samples under ETF and ITF loading conditions, respectively. The average web crippling capacity of pultruded GFRP C sections increased up to 45 % when the bearing length increased from 20 mm to 50 mm. The finite element (FE) outcomes showed an agreement with experimental results in the context of failure patterns, load-displacement profiles and web crippling capacities. Finally, equations were proposed to estimate the web crippling capacity of pultruded GFRP C sections strengthened with FEC. [ABSTRACT FROM AUTHOR]

This paper aims to present a methodology to predict the anisotropic and non-linear behaviour of glass fibre reinforced plastics using finite element methods. A material model is implemented in order to remedy the need of multiple material definitions, and to control the local plastic behaviour as a function of the fibre orientation. Injection moulding simulations traditionally provide second order orientation tensors, which are considered together with a homogenization scheme to compute local material properties. However, in the present study, fourth order tensors are used in combination with traditional methods to provide more accurate material properties. The elastic and plastic response of the material model is optimized to fit experimental test data, until simulations and experiments overlap. The proposed material model can support design engineers in making more informed decisions, allowing them to create smarter products without the need of excessive safety factors, leading to reduced component weight and environmental impact. [ABSTRACT FROM AUTHOR]

Corrosion of steel rebars is known to cause deterioration of concrete structures that can lead to catastrophic failures. To mitigate this problem, steel rebars can be replaced with Glass Fiber-Reinforced Polymer (GFRP) rebars. However, the lack of ductility of GFRP-reinforced elements has prevented their use in many structural applications, especially in seismic areas. Stainless Steel (SS) rebars are corrosion resistant and have adequate energy absorption and ductility. However, they are much more expensive than steel rebars. This paper proposes the combined use of SS and GFRP rebars to achieve ductile and corrosion-free elements. The first challenge for such a proposal relates to designing SS-GFRP reinforced concrete frame with adequate lateral performance in terms of initial stiffness, ductility, and strength. Design equations, which are based on a comprehensive parametric study, are developed to allow designing such a frame. A six-storey concrete frame is then designed using the proposed equations and its lateral performance is examined using pushover analysis. [ABSTRACT FROM AUTHOR]

Modular glass fibre reinforced polymer (GFRP) multicellular structures were formed using pultruded GFRP box sections incorporated between two GFRP flat panels by adhesive bonding. Three types of fire resistant panels, namely glass magnesium (GM) board, gypsum plaster (GP) board and lightweight calcium silicate (CS) board, were installed at the outer face of the lower GFRP flat panel using screws. The lower surfaces of the built-up specimens were then exposed to fire. The thermal responses of the GFRP multicellular specimens assembled with different fire resistant panels were measured and comparatively analysed, in association with the damage patterns observed. It was found that the fire resistant panels effectively mitigated the temperature progressions developed in the GFRP components, thereby improving the fire insulation performance of those structural assemblies. The GM board provided the best fire insulation performance, with the highest temperature at the outer face of the upper GFRP flat panel (the surface unexposed to fire) being less than 120 °C after 90 min of fire exposure. Further, the effects of cavities and end closure configurations of the multicellular assemblies on the heat transfer were evaluated and highlighted. [ABSTRACT FROM AUTHOR]

In this research, glass fibre reinforced composite laminate samples were manufactured with filament winding technique using four different vinyl ester resin systems to study ageing. The manufactured laminate samples were conditioned in an environmental cabinet (70 °C, 95 RH%), water immersion (95 °C), and in sulphuric acid solution immersion under pressure (5% H 2 SO 4 , 95 °C, 15 bar). After 6 and 12 months of conditioning, the samples were tensile tested and the results were compared with the initial values. Regardless of the matrix type, conditioning in the environmental cabinet resulted in the lowest weight gain and least decrease in tensile properties: the decrease in the tensile strength values was 10–25% after 12 months’ conditioning depending on the vinyl ester used. The water immersion was more detrimental to the samples than the 5% H 2 SO 4 immersion causing the highest weight gain and the greatest decrease in tensile strength (up to 65%). However, when comparing the tensile performance, it was noted that the highest weight gain did not inevitably correlate with the strongest ageing effect. In water immersion, the ultimate strength deteriorates faster than the proof stress level leading to a decreasing damage tolerance of the vinyl-ester composite laminates. [ABSTRACT FROM AUTHOR]

Fiber Reinforced Mortars (FRM) represents a promising technique for the in-plane and out-of-plane reinforcement of existing masonry buildings, coupling effectiveness with compatibility needs. The paper focuses on a technique consisting in the application on the masonry surface of a 30 mm thick mortar coating with Glass Fiber-Reinforced Polymers (GFRP) meshes embedded, presenting and discussing the results of several characterization tests (pull-out, lap-splice, bond and tensile tests) performed so to investigate on the tensile properties and bond performances of the strengthening system, useful for correct design procedures and suitable also for numerical modeling. The main aspects that has to be taken into account in the design of characterization tests are evidenced and the influence of some fundamental parameters (as the clamping system, the anchorage length, the boundary conditions and the sample dimensions) is discussed. Moreover, proper characterization tests permitted the estimation of the anchorage length to make effective the reinforcement and the definition of the stress-strain curve of the reinforced material subjected to tensile force. [ABSTRACT FROM AUTHOR]

Structural damage identification has been researched for a long time and continues to be an active research topic. This paper proposes the use of the natural frequencies of a novel composite structures made of glass fibre reinforced polymer (GFRP). The proposed methodology consists of an improved Artificial Neural Network (ANN) using optimization algorithms to detect the exact crack length. In the first step, the characterization of fabricated material is provided to determine Young's modulus using an experimental static bending test, tensile test and modal analysis test. Next, numerical validation is performed using commercial software ABAQUS to extract more data for different crack locations in the structure. The comparison between experimental and numerical results shows a good agreement. ANN has been improved using recent optimization techniques such as Jaya, enhanced Jaya (E-Jaya), Whale Optimization Algorithm (WOA) and Arithmetic Optimization Algorithm (AOA) to calibrate the influential parameters during training. After considering several scenarios, the results show that the accuracy of E-Jaya is better than other optimization techniques. This study on crack identification using improved ANN can be used to investigate the safety and soundness of composite structures. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of pultruded glass fibre reinforced polymer (GFRP) circular hollow section (CHS) columns under concentric and eccentric compression. The member slenderness of the selected columns was in the short, intermediate, and long range, and two different eccentricities were chosen within the column's cross section. Predominant failure modes observed in the experiment include longitudinal splitting and localized delamination buckling. The load-carrying capacities of the concentric column under different slenderness values were quantified and compared with existing design rules. Under eccentric loading, the ultimate loads of the columns decrease with increasing eccentricity and slenderness, and the load–strain behaviour displayed non–linear characteristics due to geometric non-linearity. Failure modes of all the tested columns were well predicted by the FE models, and it was found that splitting material failure was due to hoop matrix tensile rupture. [ABSTRACT FROM AUTHOR]

Steel plate connection is popular in modern timber structures. However, the steel plate may be subjected to corrosion issue due to the presence of moisture in timbers. This paper proposes to replace steel plate with glass fiber reinforced polymer (GFRP) plate for connecting timber elements, so that the durability of the timber structure is expected to be improved. An experimental study is presented on the static and fatigue performances of the proposed GFRP-timber bolted connections. Variables including bolt diameter, number of bolt rows, number of bolt columns were selected to understand their effects on the static and fatigue behaviours of the connections. Failure modes, load–displacement curves, static bearing capacities, fatigue lives, stiffness degradations of the GFRP-timber bolted connections were reported. The residue bearing capacities of the connections were tested after the fatigue loading tests to assess the fatigue effect on the connection static behaviour. This study contributes to the understanding of the mechanical behaviour of GFRP-timber bolted connections. [ABSTRACT FROM AUTHOR]

This work presents an experimental and a numerical studies on the effect of the phenomenon of porosity on the mechanical properties of Glass Fiber Reinforced Polymer (GFRP). In a first part, material elaboration, as well as its characterization using a three-point bending test to extract the basic mechanical properties of the material, is considered. In a second part, a finite element model is created to simulate the problem of air bubbles broadly. Several cases of different shapes and sizes are simulated. The results show a significant effect on the reduction of load in both tensile and bending cases as the size of the bubbles increases. Furthermore, the second part includes the application of the Artificial Neural Network-Enhanced Jaya Algorithm (ANN-E JAYA) to predict the reduction of the tensile load as a function of different crack lengths obtained from an Extended Finite Element Method (XFEM) model. Next, to verify the accuracy of provided application , a comparison is made with two other applications such as Artificial Neural Network-Jaya Algorithm (ANN-JAYA) and Artificial Neural Network-Particle Swarm Optimization (ANN-PSO). The results of the three algorithms show good convergence, with a slight increase in accuracy for ANN-E JAYA. MATLAB code and data used in this article can be found at https://github.com/Samir-Khatir/GFRP-ANN-E-JAYA.git. [ABSTRACT FROM AUTHOR]

This work presents an experimental and a numerical studies on the effect of the phenomenon of porosity on the mechanical properties of Glass Fiber Reinforced Polymer (GFRP). In a first part, material elaboration, as well as its characterization using a three-point bending test to extract the basic mechanical properties of the material, is considered. In a second part, a finite element model is created to simulate the problem of air bubbles broadly. Several cases of different shapes and sizes are simulated. The results show a significant effect on the reduction of load in both tensile and bending cases as the size of the bubbles increases. Furthermore, the second part includes the application of the Artificial Neural Network-Enhanced Jaya Algorithm (ANN-E JAYA) to predict the reduction of the tensile load as a function of different crack lengths obtained from an Extended Finite Element Method (XFEM) model. Next, to verify the accuracy of provided application , a comparison is made with two other applications such as Artificial Neural Network-Jaya Algorithm (ANN-JAYA) and Artificial Neural Network-Particle Swarm Optimization (ANN-PSO). The results of the three algorithms show good convergence, with a slight increase in accuracy for ANN-E JAYA. MATLAB code and data used in this article can be found at https://github.com/Samir-Khatir/GFRP-ANN-E-JAYA.git. [ABSTRACT FROM AUTHOR]

In this investigation, full-scale reinforced-concrete (RC) circular-beams with glass fibre reinforcement polymer (GFRP) bars and spirals were modeled using nonlinear finite element (FE) program. All the specimens had 3000-mm length. The RC-beams were modeled in a three-dimension space, taking into account the material nonlinearity and the elastic plastic behavior of the concrete, in addition to the elastic characteristics of the GFRP materials. The results of the numerical analysis were verified by comparing them against experimental results of six similar previously tested specimens, that had 500-mm diameter. The analysis included tracing the load-deformation response of the RC circular-beams, load-strains behavior on the surface of the concrete as well as the strains in the GFRP bars. The outputs from the FE analysis showed that the program was able to foresee the experimental results with good precision. The, average, value for the experimental shear strength to the foreseen ones by the FE program, (V exp /V Model) for the six beams, is "1.00 ± 0.05″ with 2.5% COV. After ward, a parametric study was performed to expand and evaluate more parameters such as size effect (200, 300, and 400 mm), span-to-depth (a/d) ratio from 1.5 to 3.5, and spirals' reinforcement ratio between 0.32 and 1.27%. The numerical investigation confirmed the prominent effect of these parameters on the shear strength and behavior of the GFRP-RC circular-beams. [ABSTRACT FROM AUTHOR]

An innovative hybrid sandwich slab for the rehabilitation of floors in old masonry buildings was conceived, designed, and tested. This structural system is a lightweight composite floor consisting of bottom skin and shear ribs in Glass Fiber Reinforced Polymer (GFRP), a top layer of Deflection Hardening Cement Composites (DHCC), and Polyurethane foam core. In the first part of this study, the material/structural performance of the panel’s concept was assessed by experimental tests. The second part is now dedicated to the execution of advanced numerical simulations, including parametric studies, for assisting on the optimization of this composite slab system and investigating the influence of the relevant characteristics of GFRP and DHCC components. The influence of considering orthotropic behavior for the GFRP components and linear or nonlinear behavior for the DHCC are also investigated numerically in terms of accomplishing serviceability and ultimate limit state requisites for this structural system. The parametric studies show that the thickness of GFRP rib is the most important parameter to increase the load carrying capacity of this type of slabs. Based on the results of these parametric studies, two slabs are built and tested experimentally, and the obtained results are not only used to demonstrate the effectiveness of the developed structural system, but also to appraise the predictive performance of the constitutive models adopted in the FEM-based simulations. [ABSTRACT FROM AUTHOR]

This paper reveals the influence of arching action on the shear behaviour of glass fibre reinforced polymer (GFRP) reinforced laterally restrained concrete slabs in bridge decks. A total of seventeen full-size one-way concrete slabs were constructed and tested in this study. Those restrained test slabs represents typical full-scale dimensions of a real bridge deck slab 400 mm wide by 2400 mm long and 200 mm deep. The test variables were lateral restraint stiffness, reinforcement configuration and concrete strength. The behaviour of test slabs was discussed and the influence of those structural parameters on the amount of arching action was evaluated by comparing the results of different specimens. The test results showed that increasing the arching effect resulted in shear failure mode and larger shear strength. The experimental shear strengths of the restrained test slabs were compared with some theoretical predictions in the literatures. The results indicated that those theoretical methods yielded high conservative predictions. A theoretical model that takes into account the effect of arching action in the shear-strength prediction was proposed by the writers. This method provided accurate and slightly conservative predictions. [ABSTRACT FROM AUTHOR]

Thirty-six, four-point flexure tests on simply supported pultruded glass fibre reinforced polymer composite (GFRP) Wide Flange (WF) beams with mid-span bolted splice joints are described. The joints were fabricated with two and six pultruded GFRP splice plates. Three splice plate lengths were investigated and two bolt torques were used to tighten the bolts. Each of the twelve splice joint combinations was subjected to three repeat tests up to the serviceability deflection limit. Their load versus deformation responses were shown to be linear and repeatable. During each test loads, support rotations, splice joint end rotations and mid-span surface strains were recorded for each mid-span deflection increment. The beams’ transverse stiffnesses and splice joints’ rotational stiffnesses were derived from the test data. The variation of the stiffnesses with splice plate length, number of splice plates and bolt torque was also quantified. A simple analysis was developed for splice-jointed beams and was used to predict the transverse and rotational stiffnesses determined from the test data. It was shown that the transverse stiffnesses could be predicted to within 10%, provided a rigid-body rotational correction was applied. The correction also provided an estimate of the splice joint’s slip displacement. [ABSTRACT FROM AUTHOR]

• A large database of FRP-NSC columns is constructed from the literature. • Previous models for axial strength of FRP-NSC columns are evaluated. • Empirical and ANN model are proposed for axial strength of FRP-NSC columns. • The proposed empirical and ANN models portrayed higher accuracy compared with previous models. Previous research is deficient in the theoretical estimation of the axial load-carrying strength (ALCS) of glass fiber reinforced polymer (GFRP) composite columns. This study aims to calculate the ALCS of GFRP normal strength concrete (NSC) columns (GFRP-NSC) using two different approaches; empirical modeling and artificial neural networks (ANNs). The geometric, material, and testing details of 250 GFRP-NSC columns were collected from the previous studies. An initial assessment of the previous strength models for the ALCS of GFRP-NSC columns was accomplished over the constructed database. General regression and curve-fitting were used for suggesting an improved empirical model. The various hidden layers and neurons were calibrated to find an improved ANN model. Both new empirical and ANN models showed higher accuracy than the previous model for capturing the ALCS with R2 = 0.740, and R2 = 0.882, individually. A comparison of the predictions through one-way analysis of variance (ANOVA) at a 5% significance level depicts that the proposed models presented a higher accuracy than the previous models for capturing the ALCS of GFRP-NSC columns. Additionally, a detailed parametric investigation of GFRP-NSC members was carried out using the suggested empirical model to explore the influence of different variables of studied members. [ABSTRACT FROM AUTHOR]

Pultruded glass fibre reinforced polymer (GFRP) composite wide flange (WF) beams were fabricated with mid-span splice joints. The joints comprised: two or six GFRP plates bolted to the flanges. The bolts were torqued to 3, 20 and 30 Nm. The 2.9 m span simply supported spliced beams were tested in symmetric three-point flexure. Each beam was subjected to three load – unload cycles and loads, mid-span deflections, support rotations and splice plate surface strains were shown to be linear and repeatable. Spliced beam transverse stiffnesses were quantified as functions of bolt torque for both splice plate configurations and were shown to increase linearly as the bolt torque increased. Transverse stiffnesses of unspliced and six-plate bolted/bonded splice jointed beams were compared and the stiffness of the splice bonded beam was shown to be about 47% stiffer than the splice bolted beam with a bolt torque of 3 Nm. [ABSTRACT FROM AUTHOR]

Abstract: A multiaxial fatigue damage model for fibre reinforced polymer composite materials is presented. The model combines (i) fatigue-induced fibre strength and modulus degradation, (ii) irrecoverable cyclic strain effects and (iii) inter-fibre fatigue. The inter-fibre fatigue aspect is based on a fatigue-modified version of the Puck multiaxial failure criterion for static failure. The model is implemented in a user material finite element subroutine and calibrated against fatigue test data for unidirectional glass fibre epoxy. A programme of uniaxial fatigue tests on quasi-isotropic glass fibre epoxy laminates is presented for validation of the novel fatigue damage methodology. The latter is successfully validated across a range of stress levels. [Copyright &y& Elsevier]

Pultruded Fiber-Reinforced Polymers (FRP) are innovative structural elements that are experiencing a steady increase in use for different structural applications. Due to their appealing properties that set them apart from traditional construction materials, such as magnetic transparency and excellent strength-to-weight ratio, numerous experimental and numerical studies have been performed in the last decades to assess their performance as structural components. The description of the micro- and macro-scale mechanical features of FRP elements requires multiple levels of information to be accurately characterized to predict their strength, and as a result, researchers have developed computational models with varying levels of complexity to parametrize their response and investigate design parameters through numerical simulations. This paper presents a critical review of the current state-of-the-art in numerical modeling of structural fiber-reinforced polymeric elements for the prediction of their mechanical behavior under serviceability and failure limit state conditions, with particular attention devoted to pultruded Glass Fiber Reinforced Polymers (GFRP), and their use as load-bearing structural elements. The most commonly adopted numerical methods for the solution of this set of problems range from classical Finite Element Method (FEM) approaches to eXtended Finite Element Method (XFEM), Virtual Crack Closure Technique (VCCT), Cohesive Zone Modeling (CZM), Multiscale Reduced Order Modeling (ROM), as well as Random Lattice Modeling (RLM) techniques recently developed by the co-authors. Each one of these methods has its own distinctive features and brings specific challenges and capabilities that will be presented and discussed in detail in the manuscript. This paper, therefore, aims at illustrating the reliability of existing numerical models for the simulation of FRP structural elements and draw conclusions and recommendations for future research, discussing 160 references from the available literature. [ABSTRACT FROM AUTHOR]

Abstract: Fiber reinforced polymer (FRP) composites have been favorably noticed as state-of-the art construction materials, but sufficient material and structural data about FRP applications are not available. This study was intended to evaluate the applications and safety of FRP deck systems, which are developed by laboratory testing (static and fatigue tests), field application and testing of glass fiber reinforced polymer (GFRP) deck systems made of glass fiber and vinyl ester resin. The results show that the developed FRP deck systems have the expected strength and stiffness to replace the existing systems. FRP deck systems can effectively shorten the construction time and reduce the equipment required. In addition, it is determined that there is a need to evaluate the long-term structural behavior and durability of FRP deck systems in order to obtain comprehensive data for preparing the future design, manufacturing and construction materials. [Copyright &y& Elsevier]

Abstract: This paper outlines a study on the fracture behaviour of a glass fibre reinforced polymer T-joint commonly used in composite marine vessels. Finite element analysis was conducted using the virtual crack closure technique (VCCT) to investigate the fracture behaviour of the structure. The structure analysed contained initial disbond in various locations with various sizes under a straight pull-off load. The strain energy release rate (SERR) at the disbond tips were used to predict the failure loads and crack growth mechanism of the structure. The experimental results validated the VCCT as a tool for assessing the fracture behaviour and damage criticality of such structures. It was also discovered that skewed loading affected the SERR at the crack tips which altered the fracture behaviour of such structures, therefore sensitivity analysis is recommended to enhance the prediction accuracy. [Copyright &y& Elsevier]

Abstract: Glass fibre reinforced polymer (GFRP) composites are used in a wide range of applications as a structural material. They have high specific mechanical properties but are prone to delamination as a result of manufacturing defects and impact/shock loading. The ability of the structure to continue to carry load after damage and the subsequent propensity of the damage to propagate are important considerations for the design of damage tolerant composite structures. In order to accurately predict the stability of damage under load, relevant mechanical properties of the material must be accurately determined. In particular, mixed mode fracture toughness data is required in order to study the damage criticality in such structures. This paper describes an experimental study to determine Mixed Mode fracture toughness for thick glass/vinylester specimens. The test methodology used for the experiments and its difficulties will be discussed. Mixed mode fracture toughness results are presented, as are Mode I and Mode II fracture toughness results obtained via Double Cantilever Beam (DCB) and End Notch Flexure (ENF) tests, respectively. [Copyright &y& Elsevier]

Axial tension–tension fatigue experiments were performed on pultruded glass fiber reinforced polymer (GFRP) plates in a laboratory environment. Different full-scale specimen shapes were examined: plate strips as-delivered, plate strips with tabs and plates in tapered form. Experiments were performed up to ten million loading cycles with different frequencies up to 12 Hz. It was observed that the specimen temperature could increase during fatigue test. This increase was dependent on the loading frequency and the loading range. S–N fatigue life curves were determined. Tapered specimens showed a higher fatigue life than as-delivered specimens; and as-delivered specimens showed higher fatigue lives than tabbed specimens. A degradation rate of 3–5% of the single-cycle ultimate tension strength (UTS) per decade of fatigue cycles was observed. This observation is not consistent with a characteristic slope of 10% UTS/decade as shown from many previous studies.A loss of specimen stiffness up to 50% during the fatigue experiments was observed and can only be explained by considerable fiber failures. This finding is consistent with results from previous studies showing that fatigue failure of fiber-reinforced polymer composites is basically fiber dominated.The fatigue behavior of the plates was compared with the fatigue behavior of adhesively bonded double-lap joints made from the same plates. Plates and joints showed converging fatigue life curves and the same fatigue limit at approximately 25% of the single-cycle failure load at ten million cycles. [Copyright &y& Elsevier]

A generalized boundary-continuous displacement based double Fourier series solution to the boundary-value problem of free vibration of thin anisotropic fiber reinforced plastic (FRP) rectangular plates is presented. The transverse vibrational characteristics of laminated anisotropic plates with arbitrary combinations of admissible boundary conditions are theoretically investigated. Numerical results presented here pertain to the natural or resonant frequencies of five-layer symmetric cross-ply plates with all edges clamped, and rotated cross-ply anisotropic plates with all edges simply supported, which are, in turn compared with the corresponding experimental results for two sets of glass fiber reinforced plastic (GFRP) thin anisotropic rectangular plates, fabricated using two different techniques. The influence of possible defects generally encountered in the fabrication process on the experimentally obtained resonant frequencies is also discussed here. [Copyright &y& Elsevier]

Using glass fiber reinforced polymer (GFRP) bars as the reinforcement of concrete structures is becoming more and more popular. Carbon/glass hybrid-fiber reinforced polymer bars (HFRP bars), formed by wrapping a thin layer of carbon fiber reinforced polymer (CFRP) on GFRP bars, is expected to have better durability than GFRP bars. In order to evaluate the effects of CFRP layer on the durability of GFRP bars, the water absorption behaviors of both GFRP and HFRP bars were characterized, and the interlaminar shear strength degradation of GFRP and HFRP bars aged in alkaline solution was investigated with short beam shear test. The results indicate that after being aged in alkaline solution, the remaining interlaminar shear strengths of HFRP bars were larger than that of GFRP bars. And, the deterioration of HFRP bars aged in alkaline solution was found occurring at the CFRP/CFRP interface. The long-term interlaminar shear strength of GFRP and HFRP bars aged in alkaline solution was predicted using the Arrhenius theory. The present study shows that the CFRP layer enhances the durability of GFRP bars in alkaline environment, due to the delayed water and OH– diffusion in CFRP and the better alkaline resistance of CFRP. [ABSTRACT FROM AUTHOR]

Arranging a hybrid combination of longitudinal fiber reinforced polymer (FRP) bars and longitudinal steel bars in the tensile zone of a concrete beam is able to sufficiently exploit the superior properties of both FRP and steel materials to achieve a satisfactory ductility level. As the foundation of analysis and design of hybrid FRP-steel reinforced concrete (RC) members, study of tensile behavior of concrete chords with FRP-steel reinforcement is essential and necessary. In this paper, the average crack spacing of hybrid (Glass Fiber Reinforced Polymer-GFRP and steel) RC chords is analytically estimated. Subsequently, the Tension Chord Model (TCM) is extended to predict the tensile behavior of hybrid GFRP-steel RC chords. Finally, the presented models are effectively validated by experimental results of concrete chords reinforced with GFRP bars and steel bars in different combinations available in the literature, and detailed discussions about analytical and experimental results are also performed. [ABSTRACT FROM AUTHOR]

• The depth effect of NSM grooves of strengthened beams was studied. • The effect of horizontal distance between two NSM grooves was studied. • An analytical model is proposed to predict the above effects. In this paper, the effect of interaction between near surface mounted (NSM) strips and internal reinforcement on the structural behavior of upgrading RC beams has been studied. The position, arrangement and area of NSM glass fiber reinforced polymer (GFRP) strips have been examined experimentally. Six strengthened beams in addition to one control beam were tested in flexural until failure. The load carrying capacity, deflections and the mode of failure of strengthened beams were recorded. The experimental results showed that the installed NSM GFRP side by side has a lower interfacial stress than those installed separated. This improvement is more obvious in the case of NSM strips installed near the internal reinforcement. Furthermore, the installed NSM strips in deep groove experienced higher load carrying capacity than those installed in shallow groove for both patterns. The installation of the NSM GFRP strips in deep grooves using epoxy may be delay or prevent the peeling/debonding failure. The ultimate load of the beam upgraded with one NSM strip adjacent to the stirrups (in deeper groove) is about 1.5 times that of one NSM strip installed near the bottom surface of the beam. This ratio decreased with increasing the area of NSM GFRP strips. [ABSTRACT FROM AUTHOR]