International Concrete Abstracts Portal

This study investigated the flexural behavior of innovative precast self-consolidating concrete stadium bleacher units with an L-shaped cross section and reinforced with glass fiber-reinforced polymer (GFRP) bars. Six full-size reinforced concrete stadium bleacher specimens with a width, height, and thickness of 950, 390, and 150 mm (37.4, 15.35, and 5.9 in.), respectively, and with a total length of 4200 mm (165.4 in.) were tested under four-point bending load up to failure. Six specimens were fabricated: three with normal concrete and sand-coated GFRP reinforcement with three different reinforcement ratios, and three with fiber-reinforced concrete (FRC) and sand-coated GFRP reinforcement. The test parameters included GFRP reinforcement ratio and concrete type. The test results were analyzed based on the cracking and ultimate moment specified in the existing FRP design codes. The comparison shows that the experimental moment capacities of the bleachers were generally conservative in the design standards. Moreover, the reinforcement ratio had a substantial impact on the serviceability performance of the bleacher specimens. Increasing the ratio of flexural reinforcement led to reduced crack widths and decreased deflections. Changing the concrete type from normal to fiber with the same bar size showed improved serviceability and moment capacity results. This research enhances the understanding of precast self-consolidating concrete stadium bleacher units with an L-shaped cross section reinforced with GFRP bars subjected to flexural load and supports their use in infrastructure.

Glass fiber-reinforced polymer (GFRP) bars have emerged as a promising alternative to traditional steel reinforcement in concrete structures due to their superior corrosion resistance and light weight. These advantages make GFRP particularly suitable for use in saline environments such as for marine infrastructure, where exposure to chloride ions and harsh conditions accelerates the degradation of conventional steel reinforcement. This study investigated the durability and flexural behavior of concrete beams reinforced with GFRP bars preconditioned in simulated marine environments. Ten beams were prepared: six beams reinforced with GFRP bars conditioned in a saline solution at 60°C for 3, 6, and 12 months prior to concrete placement; and four unconditioned beams serving as controls. The experimental results revealed that the GFRP-reinforced beams exhibited negligible reductions in flexural capacity and stiffness after exposure to marine conditions, confirming their suitability for marine structural applications. In addition, theoretical calculations using the Arrhenius model were conducted to predict the long-term performance of GFRP bars over a 100-year period in tropical regions and a 150-year period in northern regions. This research enhances the understanding of GFRP’s long-term durability in aggressive environments and supports its use in infrastructure subjected to marine conditions.

Accurate prediction of bond strength between steel reinforcement and concrete is essential for assessing structural safety and durability, particularly under reinforcement corrosion where existing design codes such as ACI 408R-03 lack explicit modifiers. This study presents a physics-guided Bayesian framework that integrates dimensional analysis, probabilistic calibration, and uncertainty quantification to model bond strength while explicitly accounting for experimentally observed factors, including corrosion. Starting from a dimensionless power-law derived from Buckingham’s π-theorem, bond strength is expressed with globally interpretable exponents for embedment-to-diameter and cover-to-diameter ratios, while the scaling coefficient is adaptively modeled as a nonlinear function of experimental variables—including corrosion level, stirrup ratio, reinforcing bar type, and test method—through Random Fourier Features. Bayesian inference with Markov Chain Monte Carlo enables calibrated predictions with explicit decomposition of aleatoric and epistemic uncertainty, providing transparent insights into variability sources. Model performance and uncertainty behavior are examined through cross validation and external validation. Beyond predictive performance, posterior analysis yields a concise, physics-consistent bond strength equation that explicitly incorporates corrosion effects and quantifies uncertainty, providing a practical and interpretable tool for reliability-based assessment of reinforced concrete structures.

Prestressed concrete (PC) enables slender, economical, and durable structures, with post-tensioned (PT) precast girders widely used in bridge construction. Accurate design requires precise prediction of prestress losses, among which friction losses arising from duct curvature, wobble, and anchorage slip are most significant. Existing codes employ simplified exponential models, yet notable discrepancies persist between predicted and actual field values. This study presents full-scale experimental testing on PT precast girders used in Egypt’s Light Railway Transit (LRT) project. Prestress forces were measured using strain gauges to evaluate friction losses along tendon profiles. Results revealed that measured losses consistently exceeded code-based predictions, highlighting the influence of stress level and nonlinear variation along the tendon, factors often ignored by current provisions. Regression analysis yielded refined exponential models with improved accuracy and strong agreement with observations. The proposed refinements enhance predictive reliability and provide a foundation for updating design codes toward safer, more realistic PT concrete structures.

Openings in the vicinity of reinforced concrete (RC) slab-column connections exacerbate the susceptibility of flat plates to punching shear failure. Using Glass Fiber-Reinforced Polymer (GFRP) as flexural reinforcement may reduce punching resistance due to its low modulus of elasticity. However, GFRP headed-end bars offer greater stiffness, ease of installation, reliable anchorage, and less reinforcement congestion than bent bars. This study presents the results of five full-scale slab-column edge connections. The test parameters are the type of reinforcement (GFRP and steel), anchorage (bent and headed end), and the presence of slab openings in the vicinity of the column. All specimens exhibited sudden punching shear failure. Slabs reinforced with GFRP headed-end bars showed no evidence of anchorage failure. Openings significantly reduced punching capacity, with a similar percentage for both steel- and GFRP-RC slabs. Moreover, Canadian Standards and American codes highly underestimated the capacity of the specimens.