International Concrete Abstracts Portal

Accelerated carbonation treatment is recognized as an effective method for enhancing recycled aggregates (RA), but its potential in structural concrete, particularly with respect to seismic performance, remains underexplored. To address this gap, this study is the first to integrate mesoscale modeling with structural finite element analysis (FEA) to systematically investigate the seismic behavior of carbonated recycled aggregate concrete (CRAC) shear walls under dynamic loading. At the material scale, uniaxial compression tests on CRAC cylindrical specimens with varying replacement ratios were conducted to evaluate their stress–strain behavior and mechanical properties. A mesoscale model of CRAC was developed using a random aggregate placement method, and FEA was employed to extend the analysis of replacement ratios. At the structural scale, a CRAC shear wall FEA model was established, incorporating the material-level stress–strain relationships into cyclic lateral loading simulations. Parametric analysis revealed that increasing both the axial load ratio and the replacement ratio significantly reduced the seismic performance of CRAC shear walls, with a maximum reduction of 21.7%. Based on these findings, recommended ranges for RA replacement ratios and axial load ratios are proposed, providing practical guidance for the structural application of CRAC.

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 presents a novel framework of analysis to assess the resistance of existing reinforced concrete (RC) members experiencing spatial variability of crack patterns and spatial variability of concrete mechanical properties. The spatial variabilities are considered by using digital image processing (DIP) to map crack patterns onto three-dimensional (3-D) nonlinear finite element (NFE) models, where the concrete mechanical properties (compressive strength, tensile strength, damage, and modulus of elasticity) are spatially varied using random fields (RFs) to form random NFE (RNFE) models. The framework was developed and applied to assess a corroded RC beam (to determine the distribution of the resistance) and column (to determine the reliability of the column at the ultimate limit state [ULS]). Research findings indicate improved accuracy in assessing the resistance of the corroded members up to 20%, and the adaptivity of the developed framework for performing reliability analysis of existing RC structures.

Due to lateral load considerations, reinforced concrete flat plates—where the slab is directly supported on columns—are usually combined with other structural elements, such as shear walls. In such structures, the slab-column connections are typically designed to resist gravity loads only and the shear walls are designed to resist both gravity and lateral loads. Therefore, the shear walls and the slab-wall connections (SWCs) are part of both the gravity and lateral force-resisting systems. While past research has demonstrated that punching shear failures of SWCs can occur, the related research is limited; therefore, design codes typically do not include specific punching shear provisions for SWCs. In this paper, a punching shear design method for interior SWCs subjected to gravity load only, developed from finite element analysis results, is presented. The presented design method is an extension of those developed for interior rectangular slab-column connections.

Slabs-on-ground supporting storage racks are often subjected to concentrated uplift under building code seismic forces. While methods for determining slab-on-ground capacity for downward loads are well-defined, guidance for resistance to uplift has been limited and relies on finite element analysis. A simplified approach is presented for calculating slab-on-ground uplift capacity as a function of slab thickness, reinforcement content, and storage rack frame depth. Testing is conducted on small-scale concrete samples in bending to obtain the material properties. Model slabs are created and tested for an upward and downward force couple representing concentrated seismic uplift on a reinforced slab-on-ground. The plastic hinge failure mechanism of the slab samples is correlated with finite element models, and straightforward formulas are developed to produce a table of uplift capacities for common storage rack and slab-on-ground configurations.