International Concrete Abstracts Portal

This paper presents post-fatigue residual punching shear strength experiments of two identical sections reinforced by glass fiber-reinforced polymer (GFRP) rebar in a large bridge deck (15.24 m x 3.89 m x 0.21 m) supported by steel girders spaced at 3.05 m. The experiment was designed to isolate the influence of fatigue loading type on residual punching shear strength. The sections have experienced 3 million cycles of service loads, one using pulsating loads (PL) and the other using rolling loads (RL). Although the RL section suffered more stiffness degradation (71%) than the PL section (54%), both had comparable punching shear strengths (Vu), within 4%. Available equations, including ACI and CSA code regulations, underestimated Vu by 24-54% because they do not account for end restraints, which generate compressive membrane effects that significantly increase the punching shear capacity of concrete slabs. Nonlinear finite element analysis was conducted and used to examine interactions between multiple loading axles as well as offset of the loads from the center. Vu under 2 half axles spaced at 1.2 m (i.e., the 2 axles likely to interact in design truck CL-625 of the Canadian Highway Bridge Design Code) increases by only 34% compared to a single load.

Hollow concrete columns (HCCs) are an effective structural system in construction, offering high strength and stiffness while maintaining low self-weight. Limited research to date has focused on hollow square concrete columns reinforced with fiber-reinforced polymer (FRP) bars. This paper investigates the structural behavior of hollow square concrete columns (HSCCs) reinforced with glass FRP (GFRP) bars and ties under eccentric loading. Twelve hollow square reinforced concrete (RC) columns were cast with a square cross section of 400 x 400 mm and an inner circular hollow of 150 mm in diameter and 2000 mm in height. The tested specimens were divided into three groups based on the longitudinal reinforcement ratio (1.2%, 1.6%, and 2.9%). Each group consisted of four identical columns tested under four levels of eccentricity (e/h = 10%, 20%, 40%, and 80%) to investigate their influence on the structural behavior of the columns. The test results reveal that the eccentricity level had a more significant effect on the structural performance of these columns than the reinforcement ratio. The failure mode of the specimens tested under low eccentricity levels was compression-controlled, starting with concrete crushing. Contrarily, the failure mode of the specimens tested under high eccentricity levels was tension-dominated failure. Furthermore, increasing the eccentricity level from 10% to 20%, 40%, and 80% decreased the axial load capacity of the column by approximately 13%, 52%, and 80%, respectively. Lastly, increasing the reinforcement ratio enhanced the post-peak behavior of the columns. These findings offer critical insights into the structural behavior of hollow square concrete columns (HSCCs) reinforced with GFRP bars and are expected to guide design engineers and contribute significantly to North American standards and design guidelines for HSCCs reinforced with GFRP reinforcement.

Limited studies explored the shear friction behavior of reinforced concrete (RC) elements using glass fiber-reinforced polymer (GFRP), mostly using bent bars. This study investigates the behavior incorporating GFRP headed-end bars with varying reinforcement ratios and interface conditions. Twenty-one push-off specimens were tested to evaluate the influence of interface condition (i.e., as-cast, intentionally roughened, and monolithic joints), reinforcement type (i.e., steel stirrups, GFRP headed-end bars), and ratio (0.33 to 1.00%). The results revealed that interface condition and reinforcement stiffness significantly impact the behavior. Surface roughening slightly increased the capacity of the GFRP-RC specimens by 2 to 23%, while the monolithic GFRP-RC specimens reached peak loads up to 118% higher than the as-cast specimens. The GFRP-RC specimens exhibited significant load recovery, with secondary peak loads exceeding the first peak by up to 60%. Comparisons with existing models indicated that, in most cases, they inaccurately predict the capacities when GFRP connectors are utilized.

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 via 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, rebar 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.

An experimental investigation was conducted to examine the behavior of reinforced concrete (RC) beams subjected to service loads coupled with corrosion of the main flexural reinforcement. A total of nine beams with dimensions of 145 x 250 x 1800 mm (5.71 x 9.84 x 70.87 in.) were constructed. The main test variables were corrosion current density and level of service loading. The beams were loaded under a four-point bending test to either 60, 40, or 0% of the beam ultimate capacity. Applied loads and reinforcement corrosion were sustained until the failure of beams. Test results indicate that the failure of corroded RC beams becomes brittle, resulting in premature rupture of corroded steel bars. This behavior is attributed to the development of localized corrosion at sections with flexural cracks in beams. Furthermore, it was found that beams subjected to higher levels of service loading experienced further reductions in ultimate load capacity and ductility.