International Concrete Abstracts Portal

Brittle punching failures in flat plates are precluded by ensuring adequate shear strength. Typically, this is achieved by adding shear reinforcement in the design. This paper presents an experimental and analytical study of flat plates to investigate load-resisting mechanisms associated with stirrup addition. The experimental program includes four isolated flat plates with parametric variations tested under monotonic punching loads. In terms of normalized shear strength, improvements of 22% and 29% were observed in flat plates with different layouts of stirrups, respectively, when compared with the reference specimen without stirrups. The role of longitudinal and shear reinforcements in punching resistance of flat plates was assessed through strain observations. Based on test findings, a physics-based analytical procedure for punching capacity estimation is proposed and verified using a database of 72 isolated flat-plate specimens. The proposed method provided reasonably accurate capacity estimates with an overall mean test-to-estimated capacity ratio of 1.06 and a low coefficient of variation (COV) of 13%. These estimates are also compared with capacity predictions using ACI 318-19 guidelines, which resulted in an overall mean capacity ratio of 1.58 with a COV of 22%. Based on experimental and analytical results, modifications to ACI 318-19 two-way shear provisions are suggested by incorporating the key parameters in shear strength estimations, which improved the prediction accuracy to a mean of 1.25 with a COV of 13%.

Corrosion—one of the major threats to the integrity of concrete structures—can consequently affect structure serviceability and ultimate limit state, possibly resulting in failure. Glass fiber-reinforced polymer (GFRP) can be used as an innovative alternative for conventional steel reinforcement in concrete structures, effectively addressing corrosion issues. In addition to its corrosion resistance and high strength-to-weight ratio, GFRP is commonly selected for nonprestressed bars and stirrups due to its cost advantage over other fiber-reinforced polymer (FRP) materials. The study endeavored to provide a comprehensive overview of the shear resistance in GFRP-reinforced concrete (RC) beams with short shear spans. The manuscript aims to synthesize and analyze shear test data based on published studies on GFRP-RC beams with a short shear span (a/d = 1.5 to 2.5). A comprehensive literature review was conducted to compile a database comprising 64 short GFRP-RC beams to evaluate the efficiency of using the strut-and-tie model (STM) for predicting the shear resistance of GFRP-RC beams. The findings reveal that ACI 318-19 STM yielded the most accurate predictions of the shear resistance of GFRP-RC beams with a/d of 1.5 to 2.5, because the current ACI CODE-440.11-22 and ACI 440.1R-15 design codes and guidelines do not include shear equations using the STM for predicting the shear resistance of GFRP-RC beams. Based on the findings of this study, the results could contribute to establishing shear equations in the upcoming revision of the ACI CODE-440.11-22 and ACI 440.1R-15 design codes and guidelines, specifically tailored for designing short GFRP-RC beams using the STM. The study also provides sufficient data to apply the STM in the design of GFRP-RC beams.

This study employs advanced nonlinear finite element (FE) modeling to investigate interface shear transfer (IST) behavior in reinforced concrete connections, a crucial factor for bridge durability and safety. The research examines shear-transfer mechanisms at the interface between precast girders and cast-in-place deck segments through three experimental methods: beam, pushoff, and Iosipescu four-point bending tests. FE simulations evaluated stress distributions, IST capacity, and failure mechanisms. Validation against experimental data shows that the Iosipescu test provides the most accurate representation of IST behavior, exhibiting a stress distribution error margin of only 1%, closely aligned with observed failure patterns. In contrast, the pushoff test showed a 30% deviation from empirical data, indicating reduced accuracy in predicting real-world IST behavior. These findings highlight the importance of incorporating the Iosipescu test into IST evaluation protocols, as its greater precision enhances design methodologies for concrete bridges, reduces structural failure risks, and informs future updates to IST-related codes.

In practical engineering, beams requiring strengthening were usually preloaded; research on their strengthening techniques directly affected structural safety and cost-effectiveness. This study investigated the flexural behavior of preloaded RC beams strengthened with prestressed carbon textile reinforced concrete (CTRC) plates using four-point bending tests. Parameters included preload levels and whether to unload during strengthening. Results showed that strengthening with prestressed CTRC plates effectively improved the service moment, ultimate bending moment, and crack resistance, and preload level and whether to unload during strengthening had no significant effect on the strengthening effect. All strengthened beams failed due to the CTRC plate rupturing, with post-failure moments reducing to the unstrengthened beam's ultimate moment level. Pre-cracking flexural stiffness decreased with increasing preload, and the stiffness after cracking was independent of the preload and strengthening method. Finally, the ultimate bending moments were evaluated using four current codes, with the Chinese code exhibiting the highest prediction accuracy.

Reinforced concrete (RC) members undergoing shrinkage are susceptible to cracking when restrained; however, studies on this behavior are limited. Thus, the main objective of this paper is to present crack-widths, crack-patterns, and shrinkage strains from an experimental study on three RC walls with aspect ratios of 3.26 and 1.08, and horizontal reinforcement ratios of 0.2% and 0.35%, as well as a rectangular tank with 0.24% reinforcement. A 3-D nonlinear finite element (FE) analysis is conducted, and the results reveal that although the model predicts strains and maximum crack-widths reasonably well, the crack-pattern differs from the experiments. The possible reasons for this difference are discussed, and a parametric study is done to propose design equations to estimate restraint factors along the wall centerline for different aspect ratios. These equations can be used to estimate the cracking potential in the design stage without the need for a nonlinear FE analysis. For L/h above four, horizontal reinforcement has a negligible effect on the restraint, and for L/h above eight, full-height cracks can be expected due to almost uniform restraint. Finally, the design codes are compared, and it is found that ACI 207.2R-07 and CIRIA C766 predict shrinkage-induced crack-widths conservatively and reasonably accurately.