Fatigue cracking in steel structures poses a significant threat to their long-term performance and reduces their fatigue life. This study examines the effect of a repair intervention using ultrahigh-modulus carbon fiber–reinforced polymer (CFRP) bonded plates applied at various stages of fatigue crack propagation and its impact on extending the remaining fatigue life. The study also investigates the effect of CFRP bond length on crack growth rates and strain distributions. Bond lengths ranged from 0.5 to 2.4 times the effective development length (75–350 mm). Machined notches simulated initial defects, and cyclic loading was applied before and after retrofitting to control damage levels. Crack growth rates were quantified using beach marking, while strain concentrations and profiles were measured using distributed fiber optic sensing. The results show that CFRP repair is effective in increasing the fatigue life of a structure. For a CFRP plate with a 225 mm bond length, the remaining fatigue life extension ratio increased from 3.2 when intervention occurred at the onset of crack propagation (i.e., 25% area loss in the notched plate) to 7.2 when intervention occurred late in life, at 95% of the total cycles to failure (59% area loss) of the control samples. However, if assessment is based on increase in total cycles (i.e., pre- plus postrepair), results show a reduction in effectiveness at late intervention.

There is increasing interest in using glass fiber–reinforced polymer (GFRP) bars for reinforcement in compressive members such as concrete columns and bridge piers. However, the understanding of their long-term compression performance in an alkaline environment remains unknown. This study investigated the durability under compression of 12.7-mm-diameter GFRP bars with different length-to-diameter ratios (4, 8, and 16) by exposing them to an alkaline solution with a pH of 12.5–13.0, simulating the surrounding concrete environment. The effect of exposure temperature (23°C, 60°C, and 80°C) and exposure duration (42, 83, and 125 days) was evaluated. The results show that the retained compressive strength of GFRP bars after exposure to a simulated concrete environment varied with length-to-diameter ratios. The degradation of the resin-rich outer surface significantly impacted the compressive strength of the GFRP bars with length-to-diameter ratios of 4 and 8 because their failure mode of fiber crushing initiated from the bar surface. The GFRP bars with a length-to-diameter ratio of 16 failed by fiber-splitting mode under buckling, initiated from inside the bar, and their compressive strength was similar to that of unexposed GFRP bars. Analysis further revealed that temperature and exposure duration were statistically significant, affecting the compressive strength of the GFRP bars with length-to-diameter ratios of 4 and 8, but not those with a length-to-diameter ratio of 16. This study provides a detailed understanding of the durability of GFRP bars under compression, which will be useful in their effective design as longitudinal reinforcement in concrete structures.

Understanding and accurately predicting the thermal behavior of fiber-reinforced polymer (FRP) composites is critical for their reliable application in structural systems. This study focuses on predicting temperature distributions within hybrid FRP sandwich panels composed of a pultruded glass fiber–reinforced polymer box, a closed-cell polyurethane foam core, and a steel fiber–reinforced self-compacting concrete topping layer. An extensive experimental program was conducted under both controlled and external environmental conditions. The controlled phase involved thermal cycling and exposure to a high-pressure sodium lamp to simulate radiant heating effects, while the outdoor phase captured real-world thermal fluctuations. Temperature was monitored using embedded PT100 sensors, and additional equipment was used to record ambient conditions, including solar radiation. Through meticulous experimental analyses and numerical simulations, this research evaluates the boundary conditions and thermal loads affecting the specimens, enabling the development and validation of numerical models. These models were designed to replicate transient heat transfer within the panels, accounting for convective heat exchange, direct and reflected radiation, and the influence of surface moisture during and after rainfall. The models achieved over 92% accuracy compared to experimental data, based on the mean absolute percentage error. Key findings show that disregarding reflected solar radiation from surrounding surfaces resulted in peak temperature underestimations of up to 13.9°C, while neglecting evaporative cooling reduced the overall accuracy by approximately 6%. These results highlight the importance of calibrated numerical models for thermal analysis, ensuring the reliability of FRP-based structures under operational conditions. Furthermore, this research offers valuable insights for defining temperature distribution assessment methodologies regarding FRP composite structures in real-world applications.

Fig. 1) grew up in Devon, England, a place for which he retained a strong attachment.He attended Exeter School and went on to study engineering at St John's College, Cambridge (1968( -1971, Fig. 2, Fig. 2).He undertook a master's degree at Imperial College, London (1971)(1972)

Glass fiber‒reinforced polymer (GFRP) bars are increasingly recognized as promising reinforcement options for seawater–sea sand concrete because of their chloride resistance. However, the internal alkalinity of concrete remains a crucial factor impacting the durability of concrete-wrapped GFRP bars in marine environments, particularly when used in prestressed applications. To increase the durability of prestressed GFRP bars in seawater–sea sand concrete, the effectiveness of reducing internal alkalinity by incorporating phosphogypsum was investigated. The accelerated aging test of GFRP bars was conducted under various exposure periods (30, 60, 120, and 240 days), temperatures (25°C, 40°C, and 60°C), and prestress levels (0% and 20%). The long-term performance of the GFRP bars wrapped with different-alkalinity concrete was evaluated. Scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis were employed to investigate the failure mode of the conditioned GFRP bars and the degradation mechanism. The results showed that 10% phosphogypsum incorporation significantly mitigated the deterioration of the GFRP bars. Specifically, the tensile strength retention after 240 days improved by 13.0%–22.3% for non-prestressed FRP bars and 5.1%–17.9% for prestressed FRP bars when wrapped with low-alkalinity seawater–sea sand concrete. Unlike non-prestressed bars, the occurrence of delaminated resin and fiber fracture is more pronounced for prestressed bars. The addition of phosphogypsum neutralizes hydroxide ions in the cement matrix and improves the mechanical strength of concrete, thereby mitigating alkali attack and inhibiting water molecule infiltration within GFRP bars. The findings provide experimental data and validation for existing theories on the durability of prestressed GFRP bars in aggressive environments, supporting future advancements in marine infrastructure design.

This study evaluated the effectiveness of using externally bonded fiber-reinforced polymer (FRP) sheets at increasing the load-carrying capacity of glued-laminated (glulam) timber beams. The investigation examined a range of strengthening configurations, including the use of U-wraps for shear strength enhancement and the combination of U-wraps and longitudinal FRP for combined shear and flexural strengthening. Parameters of interest in the study included the influence of fiber type (glass versus carbon), fiber orientation (uni- versus bidirectional FRP U-wraps), and fiber bond (bonded versus unbonded U-wraps). Consideration was also given to the influence of U-wrap anchorage on the retrofit performance. Retrofit performance was evaluated by testing eight large-scale glulam beams with a low shear-span-to-depth ratio (a/d = 2.39). Results of the study demonstrated that both the fiber orientation of the U-wraps and the bond between the FRP and wood impacted the effectiveness of the retrofit. Overall, the use of FRP U-wraps was found to increase the beam strength and ductility relative to the control beam by 1.2 and 1.7 times, respectively. The combination of U-wraps and longitudinal FRP sheets for flexural strengthening increased the beam capacity by up to 1.4 times the control beam. The results demonstrated that longitudinal FRP strains reached up to 7,000 µε, while strains in the FRP U-wraps exceeded 2,900 µε in some configurations. The distributions of the longitudinal and transverse strains in the FRP measured using distributed fiber optic sensors are also discussed.

Externally bonded fiber-reinforced polymer (FRP) composites have been widely adopted for the rehabilitation of aging bridge infrastructure in recent decades. The major reasons for the utilization of these materials in bridge rehabilitation include strength, durability, lightweight nature, design flexibility, and quick installation. However, deterioration of the bonded interface between the concrete substrate and the FRP—or between individual layers of a multilayer composite—can significantly impact the structural performance of the strengthened member or system. Therefore, it is necessary to evaluate the effectiveness and accuracy of condition assessment techniques to ensure satisfactory performance over the intended service life of the structure. This paper presents a visual inspection and detailed assessment of three full-size diaphragms from the Champlain Bridge in Canada. The diaphragms were strengthened with externally bonded carbon fiber–reinforced polymer (CFRP) sheets 5 years before the bridge was decommissioned as a result of extensive degradation after 57 years in service. The condition assessment includes nondestructive (acoustic tapping and infrared thermography) and semidestructive (direct pull-off) testing to identify surface and subsurface issues including CFRP delamination, material incompatibility, discoloration due to corrosion, interfiber cracks, and fundamental problems arising from the construction of the bridge diaphragms and installation of the CFRP. The results of 490 pull-off tests, comprising the largest single database of its kind to date, generally confirmed the results of nondestructive tests that aimed to locate hidden defects behind the strengthening layers. Microscopy of failed surfaces provides additional insights into the condition of the bond line in defective regions.