International Concrete Abstracts Portal

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.

A slag-based zero-cement concrete (ZC) was newly developed as an alternative, eco-friendly material to portland cement concrete. To investigate the bond performance between ZC and steel reinforcing bars, lap-splice tests were conducted for ZC beams. Fourteen beams (two cementitious normal concrete [NC] beams and 12 ZC beams) were tested at the ages of 6 days (45 MPa [6.53 ksi]) and 28 days (60 MPa [8.7 ksi]). For steel reinforcement, Grade 600 MPa (87.0 ksi) reinforcing bars were used. The test parameters included the concrete type, concrete strength (that is, concrete age), reinforcing bar diameter, concrete cover thickness, ratio of actual to required lap-splice length, and use of stirrups. The test results showed that the performance of ZC beams was comparable to that of the counterpart NC beams in terms of moment-deflection relationship, damage mode, and reinforcing bar stress at the peak load. This result indicates that the bond performance of ZC was equivalent to that of NC with identical compressive strength. The bar development length specified in current design codes safely predicted the reinforcing bar stress of the ZC beams at failure; current design codes are applicable to the reinforcing bar development length design of ZC members.

In the Netherlands, existing reinforced concrete solid slab bridges require assessment for shear. Skewed slab bridges form a subset of this category. Previous experiments showed that stresses concentrate in the obtuse corner, which becomes governing for shear, and that the shear capacity in skewed members is reduced. The presented series of experiments studies the shear capacity of reinforced concrete slabs under concentrated loads. In total, five skewed slabs are tested, resulting in 15 shear experiments. The parameters that are studied are the skew angle, the reinforcement layout, the distance between the load and the support, and loading near the obtuse or acute corner. The results are compared to existing calculation methods and recommendations for determining the acting shear stress and shear capacity, which lead to reasonable results. Ultimately, the insights from these experiments can be used for the assessment of existing skewed slab bridges.

This study evaluates the seismic performance of circular columns reinforced with fiber-reinforced polymer (FRP) bars, focusing on the efficacy of existing code provisions (ACI 318-19, CSA A23.3-24, CSA S806-12, and CSA S6-25) in predicting drift and moment capacities. A database of 38 full-scale columns tested under lateral cyclic loading with varying axial load levels, spiral pitches, and reinforcement types (glass fiber-reinforced polymer [GFRP]/steel longitudinal bars) was analyzed to assess code provisions, confinement effectiveness, and strength enhancements. Results demonstrate that CSA S6-25, which incorporates updated FRP compressive strain limits (0.008Ef for spirals), outperformed other codes, aligning with approximately 85% of experimental data in ideal performance quadrants. Close spiral pitch (≤75 mm [2.95 in.]) and low axial loads were critical to achieving drift ratios ≥3% and moment capacity ratios (Mmax/Mo) exceeding 2.0. Replacing steel spirals with GFRP spirals did not result in substantial variation in the seismic performance of columns. Columns with GFRP longitudinal bars exhibited comparable ductility and observed substantial increase in moment capacity (Mmax) compared to the unconfined nominal moment capacity (Mo) due to delayed bar buckling under effective confinement. However, columns with GFRP longitudinal bars observed a softer response, and the determination of the probable moment to calculate the shear demand remains questionable and requires more analytical investigations.

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.