Journal of Composites for Construction

In this paper, which focuses on the fiber-reinforced polymer (FRP) sheet bonding method for improving the impact resistance of RC beams, low-velocity impact load tests are performed on RC beams strengthened with FRP sheets. Both aramid FRP (AFRP) and carbon FRP (CFRP) sheets are used to experimentally investigate the flexural strengthening effect of the sheet materials. The impact force is created by dropping a 300-kg steel weight from various heights. The experiments are conducted using a single loading method for each beam, and the drop height of the weight is increased until the sheet debonded. The results obtained from this study are as follows: the impact-resistance capacities of the beams are improved by flexural strengthening with FRP sheets; the strengthening effects of the sheets are similar, regardless of the sheet materials, when the axial stiffness values of the sheets are equal; and the maximum and residual deflections are approximately linearly distributed with increasing input impact energy until the FRP sheets debonded.

Owing to the unique mechanical characteristics and lack of plasticity of fiber-reinforced polymers (FRPs), relatively large strains can develop in FRP reinforced concrete (RC) elements at ultimate limit states and this can lead to different relative contributions of concrete and shear reinforcement to the total element's shear capacity. This paper examines the development and relative contribution of the main shear resisting mechanisms in concrete beams with different overall depths and reinforced with longitudinal and transversal FRP reinforcement. Complementary strain measurements obtained from digital image correlation (DIC) and strain gauges are presented and discussed thoroughly. Although current FRP shear design approaches rely on the assumption that the contributions of concrete and shear reinforcement are constant up to failure, their relative magnitude is found to vary with increasing crack width. The experimental results indicate that, when minimum shear reinforcement is provided, current shear models based on a fixed truss angle approach tend to overestimate the contribution of concrete and underestimate the contribution of shear reinforcement. The use of a variable angle truss model, along with an appropriate reduction in the contribution of concrete, would lead to a more reliable estimate of the main shear resisting mechanisms and optimal design of the required amount of shear reinforcement.

The available researches on concrete columns confined with fiber-reinforced polymer (FRP) laminates have not comprehensively addressed the size effect. In this study, a three-dimensional mesoscale simulation approach that can consider concrete heterogeneities was established to explore the size effect of glass FRP (GFRP)-confined concrete columns under axial compression. The influence of constraint ratio and cross-sectional type on the failure of columns was investigated. In addition, the effect of lateral constraint on the nominal compressive strength and the corresponding size effect was quantitatively studied. The simulation results indicate that structural size has a significant influence on the nominal compressive strength of GFRP-confined concrete columns. For the present circular columns, size effect on nominal compressive strength is weakened or even suppressed as the FRP constraint ratio increases. For square columns, the presence of GFRP cannot suppress the size effect on compressive strength, since it cannot provide sufficient constraints. Furthermore, a size effect formula that can quantitatively describe the influence of lateral constraint on the size effect of GFRP-wrapped circular concrete columns was developed. Good agreement between the theoretical results and the simulation results as well as the available test results confirms the rationality of the developed size effect law (SEL).

In this paper, the structural properties and behavior of slender steel members strengthened against buckling by a hybrid system of fiber-reinforced polymer (FRP) shells filled with self-consolidating grout (SCG), in the form of buckling restrained bracing (BRB), were investigated. The goal of the hybrid system is to increase the load-carrying capacity of the slender member to reach the yielding load of the steel core through the addition of lateral support. A total of 36 small-scale specimens (27 strengthened specimens and 9 plain 25.4 mm × 6.35 mm steel cores) were prepared and tested in compression. Strengthened specimens were prepared with three different FRP shell lengths (300, 600, and 900 mm) and three outer shell diameters (41, 53, and 65 mm). A lubricant was applied to the steel core to allow the steel core to carry the majority of the axial load independently. The contribution of each component of the hybrid system to the overall load-carrying capacity was also calculated. The steel core was found to carry on average 86% of the load at yielding, with the grout and FRP carrying only 13.5% and 0.5%, respectively. A simple linear elastic model was created to predict the failure mode of the hybrid system that can also be used to design an optimized system. The model accurately predicted the failure mode for all 27 reinforced specimens. Overall, provided the hybrid FRP-strengthening system was sufficiently sized, the system was successful in changing the failure mode of the steel core from buckling to yielding.

Insulated precast concrete sandwich wall panels (IPCSWPs) are widely used in the thermal resistance systems of buildings. This paper proposes a novel I-shaped glass fiber-reinforced plastic connector for IPCSWPs. The connector is anchored in the concrete panels with steel rebar passing through reserved holes at the ends of the connector. Featuring large stiffness, bearing capacity, and low thermal conductivity, this type of connector is expected to benefit passive houses with thick insulation layers. Quasi-static in-plane shear tests were conducted to assess the performance of the connector. The relationship between failure modes, load-bearing capacity, and key parameters, such as insulation thickness and shear directions of the connector, were investigated through testing of 16 individual specimens. In addition, finite element analysis of the specimens was established using ABAQUS to simulate the tests. The results of finite element analysis were predominantly consistent with the results of the experiments. Parametric studies are conducted to supplement the tests. To enable the engineering applications of the connector, a series of formulas for the estimation of stiffness and bearing capacity of the connector were derived through theoretical analysis of testing and finite element analysis results.

The lateral impact behavior of hybrid fiber-reinforced polymer (FRP)-ultrahigh-performance concrete (UHPC)-steel double-skin tubular columns (DSTCs) was experimentally investigated in this study. Seven specimens, which had an outer diameter of 168 mm and a length of 2,000 mm, were tested under lateral impact loading. Different parameters, including the axial force level, impact energy, concrete type, void ratio, FRP tube thickness, and the presence/absence of the FRP tube, were investigated. The dynamic responses, including global/local damage modes, lateral deflection–time histories, impact force–time histories, strain–time histories, and acceleration–time histories, were investigated. The test results prove that the hybrid UHPC DSTCs exhibit very ductile behavior under lateral impact loading. The hybrid UHPC DSTCs have a higher lateral impact resistance capacity as compared to the hybrid DSTCs infilled with normal-strength concrete. The lateral impact resistance capacity of hybrid UHPC DSTCs with an applied axial force of 200 kN can be improved to some extent compared with those without any axial force. The impact energy, the void ratio, the FRP tube thickness, and the presence/absence of the FRP tube can significantly affect the lateral impact behavior of hybrid UHPC DSTCs. Furthermore, the lateral impact behaviors of hybrid DSTCs, concrete-filled double-skin steel tubes (CFDSTs), and concrete-filled steel tubes (CFSTs) were compared and discussed based on the experimental results in this study as well as in other literature studies.

Reinforced concrete (RC) coupling beams in pre-1970s coupled-wall structures often feature a small number of stirrups, and thus are susceptible to shear failure along inclined cracks. In short beams with a span-to-depth ratio smaller than about 2.5, the failure occurs along diagonal cracks and can limit the ductility of the member, which in turn limits the seismic performance of the entire coupled-wall system. To suppress diagonal tension failure, the coupling beams can be strengthened with externally bonded fiber-reinforced polymer (FRP) sheets. However, as the FRP sheets exhibit debonding and rupture, their contribution to the shear resistance cannot be evaluated without an explicit consideration of the compatibility of deformations with the existing beam. Therefore, this paper proposes a mechanical model based on deformations that predict the complete behavior of FRP-strengthened short coupling beams exhibiting diagonal tension failure, including the effects of debonding and rupture of the FRP. The model is an extension of a two-parameter kinematic theory (2PKT) for RC coupling beams and uses two degrees of freedom to evaluate the deformations of the beam. The extended 2PKT is validated with tests from the literature and is used to study the effect of FRP sheets. The model predicts the influence of existing diagonal cracks as well as the effect of the preparation of the beam edges prior to the application of the FRP sheets. According to the model, the effectiveness of FRP sheets to increase the shear resistance increases with the span-to-depth ratio of the beam. Furthermore, for the relatively short beams studied in the paper, it is predicted that U-sheets and side sheets are nearly as effective as fully wrapped FRP sheets.

In this study, a new hybrid technique for the strengthening of rectangular reinforced concrete (RC) columns under eccentric compressive loading is described, and its effectiveness is assessed experimentally. This technique combines two carbon fiber-reinforced polymer (CFRP) systems for complementary purposes: strips of CFRP wet layup sheets with a certain prestress level using a mechanical device in an attempt to introduce effective concrete confinement, and CFRP laminates applied according to the near surface mounted (NSM) technique to increase the flexural capacity of the RC columns. The effects of the cross section aspect ratio and flexural strengthening ratio of CFRP laminates were investigated in terms of the load carrying capacity of this type of RC columns. All specimens had a height of 1,080 mm, and 3 cross sections were considered, 120 × 120 mm², 240 × 120 mm², and 480 × 120 mm², representing cross section aspect ratios (large/small edge) equal to 1, 2, and 4, respectively. All columns were subjected to eccentric compressive loading until failure. The results show that the new hybrid strengthening technique can enhance the performance of rectangular RC columns in terms of load carrying capacity and ductility under eccentric loading. The cross section aspect ratio played an important role in the confinement effectiveness of the strengthened system. When the cross section aspect ratio increases, the benefits provided by the proposed technique in terms of maximum axial strength and lateral deformability at the peak load of all columns decreased. The load carrying capacity and lateral deformability of the tested RC columns increased with the flexural strengthening ratio. In addition, an analytical model is proposed to evaluate the maximum strength and the axial load–lateral displacement response of rectangular RC columns strengthened according to the newly proposed technique, and a good predictive performance was obtained.

This paper presents test results of seven large-scale circular concrete columns reinforced with either steel or glass fiber-reinforced polymer (GFRP) reinforcement. The columns measured 355 mm in diameter and 1,750 mm in length and were tested to failure under concentric, eccentric, or four-point bending configuration. Test parameters included the reinforcement type (GFRP and steel), the GFRP spiral pitch (50 and 85 mm), and varying ratios of eccentricity-to-column diameter (e/D = 0, 0.085, 0.17, and 0.34). The obtained axial capacity of the GFRP-reinforced concrete (RC) column was approximately 17% less than that of the steel-RC counterpart. However, for e/D = 0.085, the GFRP-RC column with a lesser spiral pitch exhibited approximately 10% more axial capacity than the column with a larger pitch. As the e/D ratio increases from 0 to 0.34 the axial capacity reduced by 32%, 39%, and 70% from the axial capacity of the concentric column. A “knee”-shaped interaction diagram for circular GFRP-RC columns was developed and compared with the predictions of available codes and guidelines for GFRP-RC structures.

This paper presents an experimental investigation and a stress–strain model for ultra-high performance concrete (UHPC)-filled fiber reinforced polymer (FRP) tubes under cyclic axial compression. Test results from 12 cyclically loaded and 18 monotonically loaded cylindrical specimens with different tube thicknesses, curing regimes, and steel fibers are presented. The influence of the tested variables on the envelope curve, plastic strain, and stress deterioration was clarified to establish a theoretical stress–strain model. Through a comprehensive assessment of well-known cyclic stress–strain model developed for FRP-confined conventional concrete, a new model for FRP-confined UHPC under cyclic axial compression is proposed based on a more rational consideration of the key characteristics of FRP-confined UHPC. Both the monotonic envelope response and the cyclic response showed good agreement between the analytic predictions based on the proposed model and the test results, confirming the capability of the proposed model to predict the cyclic axial behavior of FRP-confined UHPC.

The loading capacity of pultruded fiber-reinforced polymer (FRP) multibolted joints typically controls the structural design of composite structures. This study focuses on enhancing the low loading capacity of conventional unidirectional pultruded FRP-bolted joints by investigating the efficiency of three types of connection techniques: bonded and bolted joints, resin-injected bolted joints, and bolted joints with additional bidirectional FRP layers. Sixty-eight specimens of double-lap multibolted basalt FRP (BFRP) joints, constructed with stainless steel (SS), BFRP, or hybrid steel-FRP bolts (HSFRP), were tested under static, fatigue, and postfatigue static loadings. The results indicated that an increase of up to 60% in the loading capacity of the conventional bolted connection could be achieved by adopting the aforementioned three techniques. Furthermore, at a targeted fatigue life of two million cycles, the resin-injected bolted joints and bolted joints with additional bidirectional BFRP layers improved the load efficiency of the conventional joints by 24%. Additionally, the proposed BFRP and HSFRP bolts proved their reliability in replacing conventional SS bolts without affecting the loading capacity of the composite joints, regardless of the connection technique used.

Several empirical models have been introduced during the last two decades to estimate the punching capacity of two-way slabs reinforced with fiber-reinforced polymer (FRP) reinforcement. In this study, the applicability of these models on FRP-reinforced concrete (RC) slab-column interior and edge connections subjected to gravity loads is assessed. The models are also calibrated against experiments conducted previously by the authors on FRP-RC edge connections subjected to reversed-cyclic lateral loads. Test results of 68 interior and 25 edge specimens, 6 of which were tested under reversed-cyclic lateral loads, were used to evaluate the available models. Based on the analysis, a universal model capable of accurately predicting the capacity of both interior and edge specimens subjected to gravity or cyclic loads is proposed. The proposed model provided a mean test-to-predicted strength of 1.01 ± 0.14 and 1.01 ± 0.09 for interior and edge specimens, respectively. Furthermore, a design model is proposed to estimate gravity shear limits for FRP-RC connections without shear reinforcement and subjected to cyclic load.

This paper presents 3D nonlinear finite element analyses on concrete-filled steel-tube (CFST) columns subjected to lateral impact loading by considering concrete type, projectile configuration, and strengthening with carbon fiber-reinforced polymer (CFRP) laminates. The numerical outputs were validated against the experimental results with good agreement, in terms of load-displacement trace and deformation mode. Using the validated models, further studies were undertaken to examine the influence of various parameters on the impact response, which include the material property, D/t (external diameter/wall thickness) ratios, and CFRP coverage area. The numerical predictions show that increasing the impact energy enables the columns to exhibit a higher impact force for all CFST columns studied. Reducing the D/t ratio and increasing the steel-tube strength led to an increase of the impact force and a decrease of the displacement, due to the enhanced stiffness of the tube. The results also indicate that increasing the CFRP wrapping from one-third coverage of the column surface to two-third coverage increases the impact peak load and columns stiffness but reduces the lateral displacement, while the full CFRP wrapping has almost the same enhancement as does the two-third coverage.

A total of 12 experiments were carried out to evaluate the effect of prior in-plane damage on the out-of-plane response of structurally and thermally retrofitted masonry wallettes, simulating simply the behavior of upgraded masonry infills in frame structures under seismic loading. The specimens were retrofitted with textile-reinforced mortar (TRM), which in some cases was combined with expanded polystyrene as thermal insulation material. Testing comprised in-plane diagonal compression and out-of-plane bending on walls with or without prior in-plane damage. Numerical simulations were also performed using fiber modeling, and they were found in good agreement with test results. The experimental results showed that in-plane loaded walls with TRM only or TRM/insulation retrofitting outperformed significantly their nonretrofitted counterparts. Out-of-plane loaded walls with combined TRM/thermal insulation performed much better than, or at least as well as, their TRM-only retrofitted counterparts, for the case with or without prior in-plane damage, respectively.

A large number of masonry buildings have been designed to sustain gravity loads or with reference to obsolete seismic provisions. Columns are among the weakest elements, especially in historical buildings. Many experiments have been carried out over the last few decades to investigate the effectiveness of fiber-reinforced polymer (FRP) jackets for confinement. Owing to the poor chemical compatibility of FRPs with masonry substrates, a new technique based on the replacement of resin with an inorganic matrix [fabric-reinforced cementitious matrix (FRCM)] has been developed. There are very few reports available on tests conducted on FRCM-confined masonry columns, especially with reference to full-scale specimens. To fill this gap, uniaxial pure compression tests were carried out on seven full-scale limestone masonry columns. In particular, the investigation examined the effectiveness of FRCM systems based on the use of alkali-resistant glass- and basalt-fiber grids embedded in lime-based mortar. The use of an internal reinforcement provided by pultruded glass bars or helical stainless steel bars in a dry application is also analyzed.

This study examined the shear behavior of reinforced concrete (RC) beams that were strengthened with externally bonded composite reinforced mortar (CRM) layers consisting of basalt fiber-reinforced polymer (BFRP) grids and polymer cement mortar (PCM). The variable parameters included the shear span ratios (1.6, 2.0, and 2.4), strengthening materials (BFRP grids and BFRP sheets), bonding materials (PCM and epoxy resin), and angles between the longitudinal bars of the BFRP grid and the beam axis (0° and 45°). A total of 10 RC beams were cast and tested in the four-point flexural experiments. Three beams served as control specimens, four beams were strengthened with the 0° BFRP grids (one beam and three beams using epoxy resin and PCM as bonding materials, respectively), and one beam was strengthened with the 45° BFRP grids using PCM as the bonding material. The remaining two beams were strengthened with the BFRP sheets and PCM, respectively. The experimental results demonstrated that the BFRP grids effectively improved the ultimate load of the strengthened beams, and the contribution of the BFRP grids to the ultimate load was not sensitive to the shear span ratio. The RC beam strengthened with the 45° BFRP grids displayed an improved ability to restrict the development of diagonal cracks and restrain the degradation of the flexural stiffness compared to the beam strengthened with the 0° BFRP grids. Moreover, owing to the reliable interface performance between the BFRP grids and the concrete substrate, all of the BFRP grid-strengthened beams failed in shear, while the BFRP sheet-strengthened beam experienced local debonding with insufficient ductility. In conclusion, the BFRP grid was considered an effective strengthening material for RC members.

This paper presents an experimental investigation on reinforced concrete (RC) beams strengthened in shear with embedded through-section (ETS) steel and fiber reinforced polymer (FRP) bars anchored with and without a mechanical anchorage system. The responses of the beams, including the load–deflection relationship, crack patterns, modes of failure, and reinforcement strain, are discussed. In addition, the shear performances of different strengthening systems are analyzed by comparing the ETS cases with ordinary reinforcement techniques. The effects of different types of ETS strengthening are considered in the presence of varying numbers of steel stirrups. An investigation of the shear contribution of the strengthening bars is carried out to assess the applicability of existing models. An average strain equation for ETS-FRP bars is developed from original models. Comparisons of the results obtained from this paper with those reported in the literature demonstrate that the end anchored ETS strengthening system provides a significant improvement in the shear strengthening efficiency. Furthermore, the truss analogy combined with the developed average strain formulation is an effective method to predict the shear resisting force of anchored ETS-FRP bars in ETS-FRP strengthened beams.

Precast segmental concrete beams (PSBs) prestressed with external tendons have become increasingly popular. This type of structure takes advantage of both the segmental construction method and the external prestressing technique. However, corrosion of steel tendons is still a great concern, which might increase the lifecycle costs of the structure. This study presents an experimental investigation into the use of carbon fiber–reinforced polymer (CFRP) tendons as an alternative to steel tendons for segmental concrete beams to mitigate the corrosion problems. To the best of the authors' knowledge, this is the first study using CFRP tendons to externally prestress segmental concrete beams. Four large-scale, T-shaped segmental concrete beams with different types of joints and tendon materials (steel/CFRP tendons) were built and cyclically tested under four-point loading. The test results show that CFRP tendons can replace steel tendons in segmental concrete beams as an external prestressing material. All the tested beams exhibited excellent performance regarding load-carrying capacity and ductility. The type of joint had an insignificant effect on the overall flexural behavior of the beams. After the joints opened, the beams with epoxy-coated joints behaved similarly to the beams with dry joints. The beams with CFRP tendons exhibited nonlinear behavior after the opening of joints; however, the level of nonlinearity was much less than that of the beams with steel tendons. Steel tendons achieved very high stresses at the ultimate stage, which were approximately 94% of their ultimate tensile strength. However, CFRP tendons ruptured at quite low stresses, which were approximately 78% of their nominal breaking strength on average. Finally, all the existing models examined in this study predict the tendon stress and the ultimate load of the beams with steel tendons well, but they encounter large scatter for the prediction of the tendons' stress and strength of the beams with CFRP tendons.

The long-term performance of glass fiber-reinforced polymer (GFRP) bars under high levels of sustained load combined with real field conditioning has not yet been thoroughly investigated. Our experimental investigation examined the flexural behavior of concrete beams reinforced with GFRP bars subjected to a high sustained bending load after 10 years of natural aging. The experimental program consisted of eight rectangular concrete beams measuring 250 × 250 × 2,000 mm. All beams were reinforced with sand-coated GFRP bars. Four beams were subjected to a high sustained load of up to 40% of the ultimate tensile capacity of their GFRP bars with simultaneous exposure to aggressive natural weathering (temperatures ranging from −25°C to 35°C) for 10 years. The remaining four were stored in the laboratory and treated as control specimens without any loading. The conditioned beams were tested up to failure in a four-point bending setup. The results were compared in terms of load–displacement behavior, ultimate strength, displacement capacity, failure modes, and cracking patterns. In addition, the microstructure of the GFRP bars was studied to evaluate the physical changes of the bars, and their bond condition with surrounding concrete at different stress levels. The findings indicate a strength deterioration of only 16% for this early generation of GFRP bars under harsh natural conditioning and high sustained loads for 10 years. On the other hand, the bond between the concrete and GFRP bars, as well as the glass-transition temperature, infrared spectra, and interlaminar shear strength of the GFRP bars, remained unaffected. Finally, analytical approaches were implemented to predict the load–displacement behavior and crack widths of the tested beams.

This paper reports the axial–flexural test results for 12 high-strength concrete (HSC) columns reinforced with glass fiber-reinforced polymer (GFRP) rebars to evaluate the implication of using HSC. The parameters were the applied eccentricity, the longitudinal GFRP reinforcement ratio, and concrete compressive strength and investigate their influence on the load-carrying capacity, deflection, ductility, strains in the concrete and reinforcement, failure modes, and flexural stiffness. All the columns failed in a compression failure mode due to concrete crushing. The GFRP bars developed higher tensile strains in the HSC due to the axial–flexural load compared to columns made with normal-strength concrete (NSC). A minimum reinforcement ratio of 1% in the case of HSC proved practical. Increasing the reinforcement ratio to 2.5% improved the postpeak behavior and yielded a second peak for specimens tested at eccentricities corresponding to 30%, 40%, and 60% of the cross-sectional depth. This study integrated the results to develop an analytical model able to establish moment–curvature and effective-stiffness relationships. The results were also evaluated for the tested specimens and compared to the theoretical expressions used for NSC.

The size effect on the strength of reinforced concrete (RC) beams flexurally strengthened by surface bonded sheets of fiber-reinforced polymer (FRP) is studied. As the failure is neither ductile nor brittle, but quasibrittle, occurring after stable growth of large cracks with large damage zones, the transitional size effect governed by the energetic size effect law (SEL) must be expected, which the present analysis confirms. Owing to scarcity of size effect experimental data, finite element (FE) analysis is used. A powerful microplane damage constitutive model M7 for concrete, coupled with the crack band model to suppress spurious mesh sensitivity, is calibrated by fitting the existing test data to FRP-strengthened RC specimens of diverse types, and consequently is trusted to simulate the size effect. The analysis captures the debonding near the concrete–FRP interface starting at midspan or at the end of the FRP sheet. It also captures the debonding between adjacent concrete shear cracks, and the delamination of concrete cover. The causes of these different delamination modes are explained. Simple beam-type formulas, in which the size characteristic is not the beam depth but the length of the shear span, are proposed and validated by FE results. The use of single-lap shear tests to determine the bond strength is critically discussed. Finally, a good fit of a few existing limited test data on the size effect of FRP-strengthened specimens is demonstrated.

Fiber-reinforced polymer (FRP) confinement is an effective way of enhancing the mechanical properties of concrete. However, currently, a model that can predict the mechanical response of eccentrically loaded FRP-confined predamaged concrete has not been satisfactorily established. This may be primarily due to the complications and nature of the problem. An experimental and analytical investigation hitherto unavailable is undertaken to examine the mechanical response of eccentrically loaded FRP-confined predamaged concrete specimens. This analytical study intends to examine and identify the key parameters that affect the mechanical response of eccentrically loaded FRP-confined predamaged concrete. Eccentric compression tests were performed on 72 short concrete cylinders with wide variation of degree of damage and load eccentricity, but with the same FRP confinement stiffness. A new model for the stress–strain relationship of FRP-confined predamaged concrete with eccentric loading is developed. The new model thus established is capable of predicting the mechanical response of the eccentrically loaded FRP-confined predamaged concrete specimens with good accuracy.

This paper experimentally investigates the effect of using the posttensioning (PT) steel strands on the flexural performance of rectangular concrete filled fiber-reinforced polymer (FRP) tube (CFFT) beams. Eight PT beams were tested to failure in four-point bending. The main parameters are the effect of prestressed reinforcement, the glass fiber-reinforced polymer (GFRP) tube, the tube thickness, the magnitude of the prestress level, and the number of strands. The test results indicate that rectangular PT CFFT beams showed superior load–deflection behaviors and higher flexural strength compared with the non-PT CFFT designed with identical structural laminate and tube thickness. The results show that PT CFFT beams performed substantially better than PT concrete beams with the same cross-sectional dimensions and prestressing. The flexural behavior of the tested PT CFFT beams is highly dependent on the FRP tube confinement and thickness and, to a lesser extent, on the magnitude of the prestress level and the number of strands. A strain compatibility model has been developed considering the partially confined and unconfined concrete models and verified against the experimental results. The proposed model successfully predicts the flexural moment capacity of the tested beams with satisfactory accuracy on average of 1.05 ± 0.03 and 1.21 ± 0.04, respectively. In addition, it was found that neglecting concrete confinement highly underestimates the flexural strength. More investigations, however, are needed to assess the effect of a wide range of key influencing parameters to better model and understand the flexural behavior of rectangular PT CFFT beams.

The application of deicing salt on roads during the winter is one of the main reasons for steel corrosion in reinforced-concrete pavements in cold-weather regions such as Canada and the Northern United States. Steel corrosion creates internal stresses in the concrete that cause the concrete to burst. This reduces the service life of pavements and increases maintenance costs. This study presents a long-term field test of a continuously reinforced-concrete pavement (CRCP) reinforced with glass fiber-reinforced polymer (GFRP) bars located on Highway 40 West (Montreal, Quebec). The design procedures, construction details, performance, and monitoring results for a 306-m-long section of GFRP-CRCP are presented. Three different types of fiber-optic sensors were used to monitor the pavement behavior and to evaluate the long-term performance of this type of CRCP. The field inspection ran for 6 years after the time of construction, and the data covering 30 months were analyzed. The concrete crack width, concrete crack spacing and rate, concrete temperature, concrete strain, and GFRP-bar strain behavior were recorded and investigated. The GFRP-CRCP and a 94-m-long stretch of steel-CRCP on that highway were compared in terms of crack width, spacing, and rate. Site inspection showed that neither type of pavement exceeded the crack-width limit of 1.0 mm set by the available design standard for pavement structures. The crack rate of the CRCP reinforced with GFRP bars was generally lower than that with steel bars. Moreover, the field test results after 6 years under actual service conditions revealed that GFRP-CRCP provides very competitive performance in comparison to steel-CRCP. Lastly, design equations were developed and proposed to determine the longitudinal-reinforcement ratio for the GFRP-CRCP based on the available design standard.