International Concrete Abstracts Portal

This study investigates the ultimate flexural strength (UFS) of reinforced concrete beams strengthened with CFRP (RCB-SCFRP), focusing on the identification and quantification of flexural overstrength concerning the nominal flexural strength (NFS) as defined by ACI 440.2R. A total of 106 full-scale specimens tested were carefully selected from previous research, varying in concrete strength, reinforcement configurations, and CFRP materials from multiple manufacturers. Results show that ACI 440.2R provisions accurately and conservatively estimate the flexural capacity of CFRP-strengthened beams. Including CFRP transverse reinforcement (TR) resulted in a slight increase in UFS. The type of strengthening, whether preloaded and repaired or strengthened, had little effect on the UFS/NFS ratio. Steel reinforcement ratio (SRR) significantly influenced overstrength, with higher UFS/NFS ratios observed between 0.70% and 1.00% SRR. CFRP axial rigidity notably affected overstrength, with optimal performance between 0.10 and 0.50 GPa·mm. Deflection ductility was mainly affected by the rigidity of CFRP, with a 13% increase noted due to CFRP TR. A log-normal model was developed to estimate UFS for RCB-SCFRP beams based on experimental data and ACI 440.2R guidelines.

In this study, fabric formwork is used to cast I-shaped and non-prismatic tapered reinforced concrete (RC) beams that have up to a 40% reduction in concrete volume, resulting in lower embodied CO2 than a rectangular prismatic beam. The primary aim of this research is to use distributed sensing to characterize the behavior of these shape-modified beams to an extent that was not previously possible and compare their behavior to that of a conventional rectilinear beam. Four RC beams (a rectangular control and three fabric-formed sections) were tested in three-point bending. Distributed fiber-optic strain sensors were used to measure strains along the full length of the longitudinal reinforcement, and digital image correlation (DIC) was used to acquire crack patterns and widths. The results indicate that fabric-formed RC beams can achieve the same load-carrying capacity as conventional rectilinear prismatic beams and meet serviceability requirements in terms of crack widths and deflections. The longitudinal reinforcement strains along the full length of the specimens were captured by Canadian concrete design equations, which account for the effects of both flexure and shear on reinforcement demand.

There is a need to model the complete responses of shear-critical beams strengthened with embedded through-section (ETS) fiber reinforced polymer (FRP) bars. Here, a strategy is proposed to integrate two separate approaches, flexural-shear deformation theory (FSDT) for element fields and a bonding-based method for ETS strengthening, into a comprehensive computation algorithm through localized behavior at the main diagonal crack. The use of force- and stress-based solutions in the algorithm that couple fixed and updated shear crack angle conditions for analyzing the shear resistance of ETS bars is investigated. The primary benefit of the proposed approach compared to single FSDT or existing models is that member performance is estimated in both the pre-peak and post-peak loading regimes in terms of load, deflection, strain, and cracking characteristics. All equations in the developed model are transparent, based on mechanics, and supported by validated empirical expressions. The rationale and precision of the proposed model are comprehensively verified based on the results obtained for 46 data sets. Extensive investigation on the different bond-slip and concrete tension laws strengthens the insightfulness and effectiveness of the model.

Accurate prediction of the cyclic response of reinforced concrete (RC) shear walls is critical for performance assessment of buildings under wind and earthquakes. Over the past few decades, various macro-models have been developed, based on different formulations and simplifying assumptions, to facilitate large-scale modeling of RC walls. However, there is limited research on the accuracy of these models for walls with different characteristics. This study evaluates the accuracy and application range of five prevalent macro-models using experimental results from 39 wall specimens with a wide range of design variables. Analytical and experimental results are compared in terms of cyclic load deflection responses, failure modes, and a set of structural performance measures. The results indicate that while the evaluated macro-models can predict the behavior of shear walls reasonably well, there are important limitations that may restrict their application range. Strengths and weaknesses of each macro-model are identified to help engineers in selecting the most suitable analysis method based on characteristics of the wall.

This study investigated the serviceability behavior and strength of polypropylene fiber (PF)-reinforced self-consolidating concrete (PFSCC) beams reinforced with glass fiber-reinforced polymer (GFRP) bars. Five full-scale concrete beams measuring 3100 mm long x 200 mm wide x 300 mm deep (122.1 x 7.9 x 11.8 in.) were fabricated and tested up to failure under four-point bending cyclic loading. Test parameters included the longitudinal reinforcement ratio (0.78, 1.18, and 1.66%) and PF volume (0, 0.5, and 0.75% by concrete volume). The effect of these parameters on serviceability behavior and strength of the test specimens is analyzed and discussed herein. All the beams were evaluated for cracking behavior, deflection, crack width, strength, failure mode, stiffness degradation, and deformability factor. The test results revealed that increasing the reinforcement ratio and PF volume enhanced the serviceability and flexural performance of the beams by effectively restraining crack widths, reducing deflections at the service and ultimate limit states, and decreasing residual deformation. The stiffness exhibited a fast-to-slow degradation trend until failure for all beams, at which point the beams with a higher reinforcement ratio and fiber volume evidenced higher residual stiffness. The cracking moment, flexural capacities, and crack width of the tested beams were predicted according to the North American codes and design guidelines and compared with the experimental ones. Lastly, the deformability for all beams was quantified with the J-factor approach according to CSA S6-19. Moreover, the tested beams demonstrated adequate deformability as per the calculated deformability factors.