International Concrete Abstracts Portal

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.

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.

This study investigates the shear behavior of 141 lightweight concrete (LWC) beams without stirrups that were tested and reported in the literature. The specimens had different types of reinforcement (such as basalt fiber-reinforced polymer, carbon fiber-reinforced polymer, glass fiber-reinforced polymer, steel reinforcement) and types of fiber inclusion (basalt fiber, glass fiber, polypropylene fibers, steel fiber). The test results demonstrated that the main governing parameter is the shear-span-to-effective depth ratio, a/d, whereby the beams with a/d ≤ 2.5 exhibited higher shear strength. Beams with a/d ≥ 3.0 exhibited flexure-dominated behavior and brittle shear failure. Increasing the longitudinal reinforcement ratio in the range of 0.5 to 2.5% enhanced the experimental shear strength owing to a reduction in crack widths and an increase in stiffness. Steel-reinforced beams outperformed fiber-reinforced polymer-reinforced beams due to the higher stiffness of steel. Fibers had a beneficial effect on shear performance; steel fibers enhanced the shear strength by up to 125%, whereas glass fiber and basalt fiber resulted in moderate improvements in the concrete shear capacity, and polypropylene fibers primarily increased the ductility. Consequently, the shear behavior in lightweight concrete beams is controlled by geometry, reinforcement ratio, stiffness, and fiber bridging.

Applying geopolymer concrete to replace conventional Portland cement reduces CO2 emissions. Investigating the post‑creep failure behavior of geopolymer concrete is of significant engineering relevance for improving theoretical design methods and enhancing durability and safety. Therefore, this study is conducted under stress-strength ratios of 0.3, 0.45, and 0.6. It includes 18 groups of post-creep failure tests on geopolymer concrete reinforced with basalt fiber. The concrete incorporates six different fiber parameters, including dosage and length. Plain geopolymer concrete exhibits a higher creep compaction threshold in terms of stress-strength ratio. Under an appropriate stress–strength ratio, increasing the stress–strength ratio enables fibers to develop a constraining effect, which in turn improves the post‑creep failure strength of geopolymer concrete. In contrast, when the stress-strength ratio is high, the hole effect induced by the fiber offsets their reinforcing action. The ductility and toughness of concrete after creep decrease continuously as the stress-strength ratio increases.

Projectile impact on reinforced concrete (RC) slabs fabricated using steel fiber-reinforced concrete (SFRC) and slurry infiltrated fiber concrete (SIFCON) has been benchmarked through 2-D and 3-D analyses using advanced computational tools. In the simulations, the importance of concrete compressive and tensile strengths, the presence of reinforcement bars, target thickness, and fracture energy were investigated with respect to target deformation and projectile residual velocity. The obtained results were compared with experimental outcomes from three regular reinforced concrete, two SFRC, and two SIFCON specimens in terms of target crater geometry and projectile residual velocity. In general, the simulations showed that the 3-D analysis results provide good agreement with the experimental data and also better correlation compared to the 2-D analysis results. It was also observed that the compressive and tensile strengths of the concrete specimens significantly influence the crater diameter. Additionally, incorporating reinforcement bars into the models leads to improved results. The study concludes that conducting detailed material tests on specimens is essential for achieving higher simulation accuracy.