Journal of Composites for Construction

The axial capacity enhancement of square plain concrete columns due to fiber-reinforced polymer (FRP) wrap is measured through experiments as a function of the fundamental dilation property of the parent concrete. To this end, unconfined (control) and FRP-confined concrete column specimens made using stone, brick, recycled stone, and recycled brick aggregates having their own dilation properties were subjected to uniaxial compression. The dilation effect measured using the digital image correlation technique (DICT) was observed to have a distinct relation with the concrete modulus of elasticity resulting from the coarse aggregate unit weight and absorption capacities. Relations between the strengthening ratio and strain enhancement ratio with the actual confinement ratio were plotted to measure the confinement effectiveness coefficients and strain enhancement coefficients using a redefined confining pressure model. The measured coefficients are found to be distinctly lower for brick and recycled aggregate concretes than for stone aggregate concrete. This confirms the necessity of using a revised set of coefficients to estimate the effective confinement in columns of aggregates that exhibit a greater dilation property in concrete.

An experimental study on the ultimate load behavior of steel angle sections reinforced with carbon-fiber-reinforced polymer (CFRP) is described in this paper. An approach of transforming the open-angle section to a closed section is used with CFRP as a means to increase the flexural stiffness and strength. A total of 30 steel angle sections, both CFRP-reinforced and bare steel angle specimens, were tested in 4-point bending. The slenderness ratio ($b/t$), different CFRP layers, and orientation of CFRP are the parameters included in this work. The failure behavior of CFRP-strengthened angle sections is closely studied for various wrapping configurations. The results indicate a significant increase in stiffness and strength of steel angle sections when appropriate reinforcement pattern and adequate number of CFRP layers are used.

Six full-scale specimens were constructed and tested under reversal cyclic loading to study the seismic behavior of exterior glass-fiber-reinforced-polymer (GFRP) reinforced concrete (RC) beam–column joints with lateral beams. Five specimens were completely reinforced with GFRP bars and stirrups and one was reinforced with conventional steel as a control specimen. The main test variables were reinforcing materials (GFRP and steel), presence of lateral beams, different joint shear stresses, and end anchorage of beam longitudinal bars (bent and headed-end bars). The specimens were subjected to increasing seismic drifts up to failure. Test results showed that GFRP-RC exterior beam–column joints confined with lateral beams can resist joint shear stress equal to 1.1 times the square root of the concrete compressive strength up to 6% drift ratio. In some cases, the specimens showed nonlinear behavior and nonbrittle failure, contrary to what it is expected from FRP-RC structures. Moreover, the anchorage method can change the mode of failure of GFRP-RC exterior beam–column joints.

The out-of-plane bending of sandwich panels has been widely investigated, but studies on their behavior under in-plane loading are quite scarce. In this study, 18 sandwich beam specimens were tested under three- and four-point in-plane-bending. The specimens are composed of low-density polyurethane core and glass fiber-reinforced polymer (GFRP) skins on both sides. The shear span-to-depth ($a/h$) ratio was varied from 1.33 to 4.67. Two different skin thicknesses were also used, providing beam depth-to-skin thickness ($h/t$) ratios of 47 and 94. It was found that the ultimate moment reduced by approximately one third as the $a/h$ ratio increased from 1.33 to 4.67 in sandwich beams with an $h/t$ ratio of 94 and decreased by about one quarter in beams with an $h/t$ ratio of 47. Doubling the skin thickness [i.e., from $h/t$ of 94–47] increased the moment capacity significantly. The percentage increase ranged from 55 to 95% as $a/h$ increased from 1.33 to 4.67. Failure of sandwich beams occurred by skin wrinkling in compression, mostly symmetrically, where skins move in opposite directions. A simplified analytical model accounting for shear and flexural rigidities of the sandwich beam and a skin wrinkling failure criterion in compression was developed and validated against experimental results.

This paper presents a numerical model for the cyclic/seismic behavior of reinforced concrete (RC) columns retrofitted with fiber-reinforced polymer (FRP) confining jackets. Such a column model has previously been unavailable despite the popularity of FRP jacketing as a seismic retrofit method for RC columns. The proposed numerical column model is based on a recent stress-strain model for FRP-confined concrete subjected to cyclic axial compression and a hysteretic moment-rotation model to account for the effect of strain penetration of the longitudinal steel bars in the column footing (i.e., effect of fixed-end rotations). This column model was implemented into OpenSees (Open System for Earthquake Engineering Simulation) using its fiber-section force-based nonlinear beam-column element. Predictions of the numerical column model for three FRP-jacketed RC columns subjected to either double-curvature bending or single-curvature bending are shown to be in close agreement with the test results.

Attaching reinforcing material such as steel or fiber reinforced polymer (FRP) plate to the external face of concrete members is a conventional technology used for strengthening concrete structures. Generally, three mechanisms are involved in the composite action between the concrete and the attachment: adhesion, dowel action, and friction. Methods have been developed for the identification of the interfacial bond properties when only one or two mechanisms exist at the interface. However, the existing methods cannot be used when all three mechanisms coexist. A methodology for testing the bond and the corresponding data interpretation procedure are proposed in this work to identify the bond properties of the interface involving all bonding mechanisms. As the bonding mechanisms are coupled and interact with each other, it is impossible to test all of them individually and separately. The proposed test protocol involves an analytical procedure that decouples individual mechanisms from the global response curves. Furthermore, conventional bond test methods involve extensive and labor-intensive strain gauging as well as complicated data regression analyses of test results in order to obtain the bond properties. The proposed method requires only the simplest instrumentation to measure displacement and load, without strain gauging. Test data processing also involves simple graphical interpretations only, without complicated and tedious mathematical data regression analyses. Therefore, the proposed method has advantages over the existing ones and can be easily adopted in engineering practice.

A total of seven large-scale continuous concrete beams reinforced with glass fiber reinforced polymers (GFRP) bars and stirrups were constructed and tested to failure. One reference beam was reinforced with steel bars and stirrups and six beams were reinforced longitudinally and transversally with GFRP bars. Moreover, a three-dimensional (3D) finite element (FE) model was constructed to simulate the shear behavior of such beams. The beams had rectangular cross section of $200\times 300\mathrm{mm}$ and were continuous over two spans of 2,800 mm. The test variables include concrete strength and transverse reinforcement ratio. All test beams failed in shear near the interior support after significant moment redistribution. Also, the test results showed that no significant increase in the shear strength occurred when the shear reinforcement ratio increased by using a larger stirrup diameter. On the other hand, the FE models showed that increasing the transverse reinforcement ratio through decreasing the stirrup spacing is more efficient. Experimental and numerical results showed that the CSA/S806-12 code yielded better predictions compared with the ACI 440.1R-06 guidelines.

This paper investigates bolted sleeve joints for connecting tubular pultruded fiber-reinforced polymer (FRP) sections in tubular structures such as space frames. In the proposed joint, FRP profile and steel connector are telescoped and then clamped by mechanical bolts. Four batches of specimens were prepared and tested under static axial loading (tension and compression). Design parameters, namely the type of fastener (ordinary bolt or blind bolt), member size, and bolt group layout, were selected and examined. During experiments, failure modes, load-displacement and load-strain relationships were recorded to evaluate the joint performance. A staggered pattern within a bolted sleeve joint had a negligible effect on the load distribution compared with a nonstaggered pattern. The study showed that the joint capacity could be optimized effectively by adjusting the joint geometry. When blind bolts are used, a compromise between ease of cavity fixing and joint performance must be noted. Finally, a simple analytical design model was proposed to estimate the joint capacity.

After 17 and 15 years of use, respectively, a detailed inspection of a pedestrian bridge and a 5-story building structure composed of partly adhesively bonded pultruded glass fiber–reinforced polymer (GFRP) profiles was conducted accompanied by full-scale serviceability and destructive coupon testing on exchangeable profiles. The bridge is exposed to a harsh Alpine climate and the building to a mild plateau climate. The system and material stiffness of the bridge remained unchanged during the 17 years. The material strength of the bridge, however, was significantly affected by combined freeze-thaw cycles and ultraviolet (UV) irradiation. The latter accelerated the strength degradation by uncovering the fibers (fiber blooming) and thus inducing humidity ingress into the material by wicking effects. A large majority of the small-area adhesive bonds in the bridge were intact, although a few small cracks were observed in some joints at the surface. The large-area bonds of the building did not show any damage. Based on results of the inspection of the bridge, the application of an appropriate coating on pultruded GFRP structures exposed to harsh environments is recommended.

Despite the extensive research on the debonding behavior of fiber-reinforced polymer (FRP) strengthening systems, no standard methodology has been established on its experimental characterization. To assess the performance and reliability of small-scale testing on near-surface mounted (NSM) FRP strengthening systems, an experimental program was carried out on a series of nine NSM FRP strengthening systems (bars and strips), in the framework of an international round robin testing (RRT). Eleven laboratories and seven manufacturers and suppliers participated in this extensive international exercise, which regarded both NSM and EBR FRP strengthening systems. The experimental results are discussed and compared in this paper in order to investigate (1) the bond behavior of NSM strips and bars, (2) the influence of alternative single-bond or double-bond shear pulling setups adopted by the participating laboratories, and (3) the influence in concrete strength due to different constituent materials between countries in applying a prescribed mix. The results show no significant influence of the concrete strength on both failure modes and loads. On the other hand, axial stiffness and surface treatment of the FRP NSM systems strongly affect both the bond strength and the parameters identifying the bond laws. Differences of bond strength experimentally recorded for the same FRP NSM systems tested according to different setups range between 10 and 25%. Therefore, for standard bond test protocol, the single shear bond test setup is more reliable, due to its higher feasibility compared with the double shear test setup.

Lack of understanding and confidence in the long-term performance of externally bonded fiber-reinforced polymer (FRP) composites in concrete structures still inhibits their application in repair of aged structures. While synergistic effects of multiple exposure conditions can be severe, it is generally agreed that the single most significant issue with externally bonded FRP composites is their susceptibility to degradation when exposed to moisture. This research utilized small-beam three-point bending test specimens to study FRP–concrete bond performance when subjected to accelerated conditioning environments (immersion in water and exposure to high humidity at elevated temperatures). Bond strength retention ($R_b$) was determined by dividing the conditioned strength by the average control strength. Test results from the present research were combined with other test data to form a database of over 700 test results. By utilizing an apparent analogy of FRP-concrete bonded systems to adhesive anchors, a bond durability factor (BDF) that quantifies loss in bond capacity due to accelerated conditioning is determined equivalently as a characteristic test value for adhesive anchors. Given their resistance to the environment, only carbon-fiber-reinforced polymer (CFRP) composites were examined. For the purpose of the analyses, and based on available data, it was determined that all CFRP systems may be split into three categories: wet-layup without putty, wet-layup with putty, and precured laminate. BDF corresponding to wet-layup without putty was determined to be 0.60. BDF for wet-layup with putty was not established due to the observed sensitivity to increasing conditioning temperature. CFRP laminate specimens failed prematurely by composite rupture or at the adhesive–composite interface; BDF was not determined as long term durability data corresponding to FRP–concrete bond failure mode was not available.

This paper presents an experimental and numerical study on the creep behavior of glued laminated bamboo (glubam) and carbon-fiber-reinforced plastics (CFRP)-enhanced glubam beams. Short-term mechanical tests were first carried out to determine the tensile, compressive strengths, and modulus of elasticity of glubam. Then the Burger’s creep coefficients of glubam were determined by the in-house tensile and compressive creep tests, which were carried out under different constant stress levels for 365 days. A numerical analysis procedure based on the strain-relaxation method is established to simulate the creep response of CFRP-enhanced glubam beams. Parametric studies show that increasing the amount of the CFRP laminate can effectively decrease the creep response as well as the creep stress in the glubam beam. Comparison between the numerical and the test result of a full-scale model CFRP enhanced glubam girder bridge subjected to 3.5 years creep loading also show that the numerical creep deflections can well capture the trend of creep test results.

The effect of laminate thickness on crack pattern, mode of failure, and strength of shear deficient reinforced concrete (RC) T-beams wrapped with glass fiber reinforced polymer (GFRP) laminates was studied experimentally and numerically. Eight specimens of 2.5 m span, designed to fail in shear, were tested for two point static loading. Displacements, strains, and crack pattern were monitored. The strength and mode of failure were found to depend on the crack pattern. For U wraps, increasing the fiber reinforced polymer (FRP) laminate thickness resulted in reduced web cracking and increased cracking near the free edge of the laminate.

This paper presents the first phase of an ongoing research program at University of Waterloo to study the effect of external fiber-reinforced polymer (FRP) sheet wrap confinement along a lap splice of reinforced concrete (RC) beams on their fatigue bond strength. Fatigue loading of RC beams containing a lap splice resulted in an increase in the number and width of cracks, an increase in deflection, and a decrease of the bond strength between the steel rebar and the surrounding concrete. The phase of the research described here consists of monotonic and fatigue tests of sixteen reinforced concrete beam with dimensions $2200\times 350\times 250\mathrm{mm}$. Each beam was reinforced with two 20 M bars lap spliced in the constant moment region of the tension zone and two 10 M bars in the compression zone outside the constant moment region. The test variables were the presence or absence of an FRP wrapping, the type of the FRP wrapping glass or carbon fiber-reinforced polymer (GFRP or CFRP), the type of loading, and the fatigue load range. The test results for monotonic loading showed that the stiffness of all beams was almost the same, but that the FRP sheet wrapping increased the bond strength and the deflection at ultimate load. All beams tested under fatigue loading failed by a bond failure except one CFRP-wrapped beam that failed by fatigue of the main reinforcement. The FRP sheet increased the bond strength for all specimens under fatigue loading.

Glass fiber–reinforced plastic (GFRP) composite pipes are used in many diverse applications, including oil, gas, and power plants. These pipes are subjected to various harsh service conditions during their service life. The evaluation of mechanical properties and chemical resistance of these pipes is essential to assess their long-term performance in specific applications. The results of a study to evaluate the chemical resistance and mechanical properties of GFRP pipes for application in oil and gas plants are presented in this paper. Pipe specimens were preconditioned by filling them with 7.5% HCl, 8% ${\mathrm{H}}_2{\mathrm{SO}}_4$, and a mixture of 2% NaOH and 2% ${\mathrm{KMnO}}_4$ solutions maintained at 63°C. The preconditioned and fresh pipe specimens were exposed to clean and oily water [a mixture of 10% toluene, 10% kerosene, and 80% brine water ($30\mathrm{g}/\mathrm{L}$ NaCl)] maintained at 93°C and 1.$5\times {10}^6\mathrm{Pa}$ (15 bar) pressure for 1,000 h. The fresh, preconditioned, and exposed pipe specimens were tested to evaluate their axial and hoop tensile strength, water absorption, and loss on ignition. The experimental results did not exhibit major change in the properties of evaluated pipes owing to exposure to clean and oily water at high temperature and pressure. There was minimal or no loss in the axial and hoop strength of the preconditioned or exposed pipes. The absorption and loss of ignition did not increase significantly both due to pre-conditioning and evaluated exposure conditions. The results indicate that GFRP pipes are suitable for application in the oil and gas industry.

This paper evaluated the capability of nonlinear finite-element (FE) analysis to estimate the seismic responses of reinforced concrete (RC) beam–column connections retrofitted using externally bonded carbon fiber–reinforced polymer (CFRP). As the case studies, a series of the seismically detailed scaled-down (1/2.85) specimens tested previously under either monotonic or cyclic loading were selected and nonlinear FE models were developed to regenerate the experimental results. In order to mimic the practical application in the experimental program the CFRP composites were applied on the top and bottom (flange) sides of the beam with the aim of increasing the flexural strength. The nonlinear FE analyses were performed to consider material and geometric nonlinearity whereas the material properties were obtained from the standard experimental tests on the concrete and steel reinforcements. The accuracy of the numerical results was evaluated by comparing results with those obtained from the experimental tests in terms of the load-displacement curve and failure mechanism. A good agreement was observed between the numerical and experimental results, particularly in estimating the ultimate strength and plastic hinge location of control and retrofitted specimens. Results indicated the reliability of the suggested nonlinear FE analysis as a cost-effective tool for parametric studies of RC beam–column connections retrofitted using flange-bonded CFRP.

This paper presents the results of an experimental investigation on four nonrectangular reinforced-concrete (RC) wall specimens. These specimens were damaged in previous tests with associated axial and lateral load and were subsequently repaired and strengthened with fiber-reinforced polymers (FRPs). The specimens include two L-shaped specimens and two T-shaped specimens. Results highlight that most of the strength and stiffness of the original specimens were recovered by the repair process. Compared to the original specimens, the ductility of the repaired specimens did not reduce significantly. Other aspects of the repaired wall including the failure mechanisms, hysteresis responses, deformation component, and stiffness characteristics are also discussed and compared with the original specimens. The current available methods for estimating strength and stiffness of the repaired walls with externally bonded FRPs are also evaluated and discussed based on the experimental data.

A basalt fiber–reinforced polymer (BFRP) mesh was introduced as reinforcement in high-performance concrete (HPC) thin plates (20–30 mm) for implementation in precast sandwich panels. An experimental program studied the BFRP mesh influence on HPC exposed to high temperature. A set of standard furnace tests compared performances of HPC with and without BFRP mesh, assessing material behavior; another set including polypropylene (PP) fibers to avoid spalling compared the performance of BFRP mesh reinforcement to that of regular steel reinforcement, assessing mechanical properties. Stereomicroscope observations before and after fire testing focused on the interface between HPC and BFRP mesh and its change with temperature exposure. BFRP mesh showed tendency to reduce the probability of HPC spalling without solving this issue. BFRP mesh alone leads to mechanical failure of concrete elements, requiring the use of steel. Microscope observations highlighted degradation of the HPC-BFRP mesh interface with temperature due to the melting polymer matrix of the mesh. These observations call for caution when using fiber-reinforced polymer (FRP) reinforcement in elements exposed to fire hazard.

One of the key issues associated with bonding of carbon fiberreinforced polymer (CFRP) sheets to the tension side of reinforced concrete (RC) beams is the debonding of CFRP sheets that leads to premature and brittle failure of the structural member. Surface preparation of concrete cannot, however, prevent debonding of CFRP sheets while it also has its own problems, such as high cost, environmental pollution, handling difficulties, and prolonged construction operations. In this paper, boring is proposed as an alternative method for bonding strengthening plates onto a concrete surface that not only lifts the problems associated with common methods of surface preparation but will also postpone debonding far more efficiently. A total of 42 nonreinforced concrete beams in four groups, i.e., lacking flexural strengthening, without surface preparation, with surface preparation, and with boring method were tested under four-point loading. To further investigate the performance of the boring method proposed, the effects of depth, diameter, and number of holes were also examined on the load-displacement curve. Results show that the performance of the boring method can be improved by increasing both hole diameter and section area of the anchors. There is an optimum hole depth beyond which ultimate rupture strength and ductility of tested specimens are reduced. Members subjected to boring method exhibit higher load capacities up to 35% and higher ductility improvements up to 100%.

Carbon fiber strands offer a viable alternative to corrosion-prone steel strands in posttensioning applications. This study focused on a side-by-side comparison of two types of carbon fiber strands with different elastic moduli against steel strands in a $5½:1$ scaled model of a typical interior hammerhead pier of the San Antonio Downtown $Y$ project with two identical cantilever overhangs. Two different strand arrangements were used for posttensioning, with eight and six strands, respectively representing an overdesign and a slight underdesign relative to the factored demand. The model was tested under service and factored flexure and shear loads. The study confirmed the feasibility of using carbon fiber strands in unbonded posttensioning of pier caps. Given the strength-based design of the pier cap, the elastic moduli of different carbon fiber strands did not seem to have affected the serviceability performance with respect to either cracking or deflection. Considering both serviceability and overload conditions, the general performance of the pier cap model under both flexure and shear loading was deemed acceptable using either type of carbon fiber strands, and quite comparable to that of steel strands.

This paper presents the test results of five full-scale reinforced concrete (RC) interior slab–column connections. Each specimen consisted of a 2,800-mm square slab with a thickness of 200 and 300-mm square central column stubs. Four slabs were reinforced with glass fiber–reinforced polymer (GFRP) bars and one reference slab was reinforced with steel bars. The connections were subjected to eccentric load with a moment-to-shear ratio equal to 0.15 m. The test parameters included the type and ratio of the reinforcement and concrete compressive strength. Test results revealed that increasing the GFRP reinforcement ratio or the concrete strength increased the connection capacity and decreased the deformation of the tested slabs. Moreover, the GFRP-RC connection that has similar reinforcement rigidity to the steel-RC one showed comparable capacity and deflection at failure. Test results were compared with different available models and design provisions including the Canadian standard, the American guideline, and the Japanese code. The Canadian standard and the Japanese code predicted the punching capacity of the test slabs with better accuracy compared with the American guideline.

A recently proposed technique for the recycling of concrete is to directly reuse large pieces of coarsely crushed demolition concrete (referred to as recycled concrete lumps or RCLs) with fresh concrete in new construction. This novel recycling process is simpler and more cost-effective than the traditional way of recycling concrete as aggregates. The resulting concrete, referred to as compound concrete in this paper, features greater heterogeneity, especially when the fresh and the recycled concretes have rather different strengths. The interfaces between RCLs and fresh concrete, as internal weaknesses, may also compromise the performance of the compound concrete. One possibility to improve the properties of this compound concrete is to supply it with a substantial amount of confinement as may be available in concrete-filled FRP tubes, which are attractive as columns in corrosive environments. This paper therefore presents and interprets the results of an experimental study on the compressive behavior of FRP confining tubes filled with compound concrete. The influences of various parameters, such as the mix ratio and the strength ratio between the old and the fresh concretes as well as the FRP tube thickness, are investigated. The test results indicate that with a significant level of confinement, the ultimate axial stress and the ultimate axial strain of the compound concrete containing RCLs are comparable with those of the fresh concrete, regardless of the strength of the old concrete. This conclusion is important as it means that the weaknesses of compound concrete containing RCLs can be largely eliminated through lateral confinement. The applicability of an accurate stress-strain model previously developed for FRP-confined normal concrete to FRP-confined compound concrete with RCLs is also examined.

In simply-supported reinforced-concrete (RC) beams strengthened by carbon-fiber-reinforced polymer (CFRP) plates, plate debonding is initiated at the beam ends, where the principal compression, predominantly composed of a vertical component, detaches the plate externally bonded to the unconfined cover concrete. A CFRP wrap acting as a U-clamp can provide confinement to enhance the moment capacity by resisting premature cover debonding. The wrap design parameters in terms of clamping location, width, and stiffness were identified from a set of fundamental experiments. The ultimate moment capacities of 22 tested specimens with different end anchorage conditions were compared against control specimens. The debonding strain, and consequently the ultimate moment capacity, gradually increased with increasing U-clamp width and stiffness. The failure patterns confirmed the effect of U-clamps in inducing a partial confinement effect on the sides and bottom of a beam end. The resulting changes in the compressive principal stress distribution in the compression arch were considered in formulating relationships for debonding strain prediction. The proposed relationship successfully predicted values regarding strengthened stone and brick aggregate concrete beams. The relationships for both unclamped and U-clamped anchorages better reproduced the experimental moment capacity enhancements than did the known equations. To assess the derived relations’ wider applicability, the estimates obtained using the proposed relations were compared against published results for 42 test beams.

This paper focuses on rehabilitation/strengthening of damaged concrete prisms through external carbon-fiber-reinforced polymer (CFRP) jacketing. In order to evaluate the efficiency of the strengthening method on the damaged concrete prisms, an experimental study including 22 concrete prisms with square and rectangular cross sections was carried out. The parameters of the experimental study are the damage levels. Furthermore, effects of loading scheme (monotonic or cyclic) and cross section type (square and rectangular) were investigated in the existence of damage. The concrete prisms were tested under compression stresses up to three specified axial deformation levels to be representative of slight, moderate, and severe compression damages before strengthening. Tests were repeated after rehabilitation/strengthening of damaged specimens with CFRP jacketing. Test results showed that CFRP rehabilitation/strengthening was effective on enhancement of strength and deformability of the damaged concrete prisms. However, the efficiency of the strengthening method in terms of compressive strength tended to reduce when the level of damage increased. Furthermore, an available model is modified to include the effects of damage level, and the modified model is shown to produce accurate results.

Fabric-reinforced cementitious matrices have raised a great interest for the external strengthening of historical masonries, representing a valid alternative to fiber-reinforced polymers. As the effectiveness of an external reinforcement firstly depends on the bond performance, this paper presents an experimental investigation, through double-shear tests, on the bond behavior of cement-matrix-based composites reinforced with three different textiles, namely, carbon, polybenzoxazole (PBO), and glass. Textiles and matrix specimens were experimentally tested to correlate mechanical properties of the constituent materials with the global response of the composites. The results of bond tests highlighted that PBO-fiber- and glass-fiber-based composites better exploit the mechanical properties of the textile. Observation of the failure mechanisms highlighted that debonding phenomena occur at the fiber–matrix interface. Furthermore, the effective anchorage lengths were estimated. The values of fracture energy were determined by a fracture-mechanics approach, using the experimental values of debonding loads. Finally, the values of fracture energy were correlated with the mechanical characteristics of the constituent materials.

A novel deck system is developed as an ultralightweight low profile waffle slab of ultrahigh-performance concrete (UHPC) reinforced with carbon-fiber-reinforced polymer (CFRP) bars. The proposed system lends itself to accelerated bridge construction, and has great potential for deck replacement in bridges with load restrictions, and as well for bridge widening. A total of seven specimens at two different overall depths, with single or multiple ribs and in simple or two-span configuration, were tested in two consecutive phases in this study. The results were compared to similar deck panels with high-strength steel (HSS) reinforcement from previous studies. The study confirmed that the proposed deck panel with only 102 mm overall depth and a self-weight of $0.9{\mathrm{kN}/\mathrm{m}}^2$ meets the demand for a 1,219-mm stringer spacing. The flexural behavior and failure modes of the deck are in general similar to the UHPC-HSS deck. The deck is not susceptible to punching shear of its thin slab and fails in a ductile manner. Load distribution among the ribs, whether calculated based on deflections or strains, is about 33% for the center rib, and 22 and 11% for the next two ribs.

This paper presents the physical, mechanical, and durability characterization of Tokyo Rope carbon fiber composite cables (CFCCs). Specimens were exposed to and alkaline solution (12.8 pH) for 1,000, 3,000, 5,000, and 7,000 h at different elevated exposure temperatures (22, 40, 50, and 60°C) to yield a simulated acceleration of the effect of a concrete environment. The durability performance of the Tokyo Rope CFCC tendons was assessed by conducting tensile tests on the specimens after different exposure periods. In addition, the microstructure of the CFCCs—both conditioned and unconditioned specimens—was investigated with scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) to assess any changes or degradation. The preexposure and postexposure tensile strengths of the conditioned and unconditioned specimens were used for long-term behavior/performance predictions based on the Arrhenius theory. The test results revealed that the average tensile strength retentions of the conditioned CFCCs could be affected by accelerated time and temperature. According to the predictions, even after a service life of 100 years, the tensile strength retention of the tested Tokyo Rope CFCC tendons would still be more than 90% at mean annual temperatures of 50°C (the mean annual temperature and the marine environment of the Middle East and warm regions) and 10°C (mean average temperature of northern regions).

Glass-fiber-reinforced polymers (GFRPs) are commonly used in various applications in civil-engineering projects. However, they are not common in the construction of civil-marine structures. The GFRP caisson technology was developed for the construction of two mooring dolphins in Puerto el Rosario (Fuerteventura, Spain). Ultraviolet-protected glass-fiber and epoxy resin coats were used to build a 12-m diameter, 13.3-m high cylindrical structure. A finite-element model was used to verify the sandwich composite configuration using the Tsai–Hill criteria—the shear strength of the skins and honeycomb core and the buckling and local failure modes with respect to the composite configuration. This is the first time that the two caissons were designed and built of polymeric materials and installed in a seaport. Accordingly, the construction technique marks a milestone in civil engineering because of its highly innovative nature in addition to significantly reducing the time associated with and the complexity of construction operations.