International Concrete Abstracts Portal

The challenges of deterioration and increasing maintenance costs in steel-reinforced concrete railway sleepers emphasize the urgent need for innovative, durable, and sustainable alternatives. This study evaluated the shear strength of precast concrete sleepers prestressed with basalt fiber-reinforced polymer (BFRP) rods, using normal self-consolidating concrete (NSCC) and fiber-reinforced self-consolidating concrete (FSCC). Seven full-scale specimens, each 2590 mm (8 ft, 6 in.) in length and prestressed to 30% of the tensile strength of BFRP rods in accordance with the Canadian Highway Bridge Design Code (CHBDC), were tested to assess cracking loads, ultimate strength, bond behavior, and failure mechanisms. All tests were conducted in accordance with the American Railway Engineering and Maintenance-of-Way Association (AREMA) guidelines. The results indicate that all specimens met AREMA design load requirements without visible cracks or slippage based on a train speed of 64 km/h (40 mph), annual traffic of 40 MGT (million gross tons), and sleeper spacing of 610 mm (24 in.). Comparative analysis using CSA S806-12 (R2021) design standard and ACI 440.4R-04 (R2011) design guide revealed that predictions based on CSA S806-12 (R2021) were less conservative than those from ACI 440.4R-04 (R2011) for the shear strength of BFRP prestressed sleepers. The BFRP rods exhibited excellent tensile performance, with minimal prestress losses, and their sand-coated surface ensured efficient load transfer by preventing slippage and enhancing the bond strength. FSCC specimens demonstrated delayed cracking, enhanced crack control, and ductility compared to NSCC specimens. These findings highlight the potential of BFRP prestressed concrete sleepers, particularly when combined with FSCC, as a sustainable solution for railway infrastructure, emphasizing the need for a design code refinement for BFRP applications.

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.

This paper summarizes the results of an experimental study investigating interface shear resistance through slant shear tests. A total of 54 tests were conducted on 6×12 in. (150×300 mm) cylinders with inclined cold joints. Five key test parameters were investigated: cold joint inclination, interface roughness, variation in concrete compressive strength between layers, casting age difference, and aggregate size. The test results demonstrated that the most influential parameters affecting interface shear resistance were interface roughness, casting age difference between layers, and aggregate size. Conversely, cold joint inclination and variations in compressive strength between layers were identified as comparatively less influential factors. A comprehensive analytical study was conducted, including the comparison of five current design codes. A modified approach is proposed for calculating the interface shear resistance, compatible with current design codes’ expressions. The proposed approach was validated using the experimental results generated from this study and a database of 124 slant shear test results from different research programs. Overall, the proposed approach resulted in more accurate estimations for the interface shear resistance, particularly for specimens with intermediary levels of amplitude at the interface.

Industrial facilities (such as offshore platforms, power plants, and treatment plants) are typically labyrinthine structures because they possess intricate layouts (resembling mazes or labyrinths), and most of their structural walls are interconnected. These reinforced concrete (RC) structural walls need to be designed for eight simultaneous demands. The existing US codes provide limited procedural guidance for the design of these walls. A novel Panel-based ACI (PACI) design approach for RC walls, rooted in the design concepts and formulations of ACI 349 and ACI 318.2, is proposed. The PACI approach is validated using two validation and verification (V&V) approaches. For the first V&V approach, existing experimental data is used to estimate PACI approach-based reinforcement areas, which are then compared against the reinforcements provided in the experiments (and against the reinforcement areas suggested by the EC2 sandwich model approach). Benchmarked numerical models are developed to compare the capacities of specimens using PACI-based reinforcements with experimentally observed capacities and with EC2-based reinforcement. For the second V&V approach, analytical data of publicly available design demands for real-world structures are used to estimate PACI-based reinforcements for a critical region of a nuclear power plant. Numerical models are developed to compare the capacities of the panels with PACI-based reinforcements against the design demands. The results from V&V1 approach showed that the PACI approach: (i) suggests similar reinforcement areas than those used in the experiments, with an average ratio of PACI suggested reinforcement areas over experimental provided areas of 0.97 for all 21 tests; and (ii) suggests similar reinforcement areas that those suggested by the EC2 approach, with an average ratio of EC2 based reinforcement areas, over PACI based reinforcement of 1.01 for all 21 tests as well. For the V&V2 approach, the numerical capacities of the models with PACI suggested reinforcements are greater than or equal to the design demands. The V&V studies illustrate that, despite its methodological simplicity, the PACI approach results in reinforcement recommendations that closely approximate the outcomes derived from the more rigorous procedures inherent to the EC2 approach. The design implementation of the PACI approach is also illustrated using a sample calculation.

Inverse analysis methods proposed by current standards for extracting the tensile properties of tension-hardening cementitious materials from indirect tension tests (e.g., flexural prism tests) are considered either cumbersome and can only be performed by skilled professionals 1,2 or apply to certain configurations and specimen geometries. Significant discrepancies are reported between the results of direct tension tests (DTT or DT tests) and inverse analysis methods. This has eroded confidence in flexural tests as a method of characterization of tension-hardening Ultra-High Performance Concrete (UHPC) and has motivated its abandonment in favor of DT testing. Additional concerns are size sensitivity, variability, and lack of robustness in the results of some methods. However, DT tests are even more difficult to conduct, and results are marked by notable scatter. This is why some codes allow for bending tests at least for quality control of UHPC. To address the limitations of the bending tests in providing an easy and quick method for reliable estimation of the tensile characteristic properties of UHPC, a new practical method is developed in this paper, based on a Forward Analysis (FA) of third-point bending tests. A unique aspect of the approach is that it considers the nonlinear unloading that occurs in the shear spans of the prism after strain localization in the critical region. The method was used to derive charts for direct estimation of the tensile properties from quality control bending tests, for the commonly used flexural specimen forms and material types. The goal of the study is to provide a practical alternative in the characterization of tension-hardening UHPC materials. Results obtained using the proposed FA method are in good agreement with the tensile response from DT tests. However, it is noted that due to the presence of a strain gradient in bending tests and the larger strain gauge lengths employed in some DT tests, the strain values at localization from DT tests tend to be more conservative.