International Concrete Abstracts Portal

Crack-width models are mainly calibrated for mechanically loaded members, whereas restrained through-depth thermal gradients induce compatibility moments and cracking. This paper benchmarks code-based procedures against nine end-rotation-restrained, one-face-heated beams tested by Ariyawardena et al., with ρns = 0.2–1.0%, two prestress levels, and heating up to 320 °F (160 °C) for 24 h. Predictions from legacy ACI, Frosch, CEN2004, CEN2023, MC90, and MC2020 procedures are compared with experimental maximum crack widths. A coupled thermo-mechanical FE bond–slip model is used to interpret crack-spacing limits and slip-driven crack opening. ACI-type methods are strongly conservative, CEN2023 is mostly non-conservative, and MC2020 gives the best agreement. Within this nine-beam, single-geometry benchmark, the FE-informed CEN2023 modification reduced the number of underpredicted cases from 8 to 4, decreased the mean underprediction for those cases from 0.0037 in. (0.095 mm) to 0.0017 in. (0.043 mm), and shifted the geometric mean bias factor from 0.628 to 1.042.

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.

While the layer-by-layer approach can accurately predict the moment-curvature (M-Phi) response of ultra-high-performance concrete (UHPC) beams, it is computationally intensive and cumbersome for designers. This study proposes a simplified equivalent rectangular stress-block method, aligning with conventional concrete design practices. The proposed method is validated using a database of 224 UHPC beams, including rectangular, T, and I-shaped sections, both prestressed and non-prestressed. The ratio of experimental to predicted moment capacities ranges from 0.95 to 1.13, with an overall average of 1.10 and a coefficient of variation of 16%, demonstrating good accuracy. Parametric analysis indicates that the maximum reinforcement ratio for singly reinforced UHPC beams ranges from 6 to 8%. To ensure ductile behavior and prevent compression-dominant failure in over-reinforced sections, it is recommended to provide compression-side reinforcement up to 50% of the area of primary tension reinforcement. The proposed approach offers a practical tool for UHPC flexural design suitable for researchers and practicing engineers.

Reinforcement corrosion constitutes a major threat to the durability and safety of concrete infrastructure. While the effect of reinforcement corrosion on the flexural strength and bond of reinforcement in reinforced concrete beams has been studied, more research is needed on the effect of corrosion of stirrups and longitudinal reinforcement on their shear strength. This paper focuses on the shear strength of reinforced concrete beams with a shear span to effective depth ratio  2.5. A review of experimental investigations on the behavior of reinforced concrete beams subjected to varying levels of reinforcement corrosion is summarized. The ACI CODE-318-25 shear design provisions are assessed by comparing experimental results with code-calculated strengths. Modifications to improve the safety of the current ACI CODE-318 approach are proposed to estimate the shear strength of slender reinforced concrete beams with corrosion damage.

The calculation of the nominal flexural strength of concrete members prestressed with hybrid (that is, a combination of bonded and unbonded [steel and/or carbon fiber-reinforced polymer (CFRP)]) tendons is dependent on determining the stress in the unbonded prestressed reinforcement. Current provisions in ACI CODE-318-25 are only applicable to members with either unbonded or bonded steel tendons. Additionally, while ACI 440.4R-04 is adopted for unbonded CFRP tendons, neither ACI provision addresses the use of hybrid tendons. This paper presents a closed-form analytical solution for the stress at ultimate derived based on the modified deformation-based approach (MDBA) that is applicable to beams prestressed with unbonded, hybrid (steel or FRP), external with deviators or internal tendons, with and without nonprestressed reinforcement. An assessment of its accuracy and applicability in calculating the nominal flexural strength is examined using a large database of 330 beams and slabs (prestressed with steel and/or CFRP tendons) compiled from test results by the authors as well as those available in the literature. Results predicted by the proposed approach exhibited excellent accuracy when compared to those predicted using ACI CODE-318 or ACI 440.4R stress equations. They also show that the approach is universally applicable to any combination of bonded and/or unbonded (steel and/or CFRP) tendons, span-depth ratio, and loading applications.