International Concrete Abstracts Portal

Due to the low lateral stiffness of slabs supported on columns alone reinforced concrete flat plates are typically combined with other structural elements, such as shearwalls. In these structures, the slab-column connections are designed to carry gravity loads only, and the shearwalls, which also carry gravity loads, are required to resist the lateral forces. Therefore, the slab-wall connections (SWCs) are essential for the adequate performance of both the gravity and lateral force resisting systems. However, the majority of punching shear research and design provisions have been focused on slab-column connections, even though punching failures around slab-wall connections have been observed experimentally. Empirical testing of slab-wall connections is difficult due to the required specimen size. This paper investigates the punching shear behaviour of interior slab-wall connections subjected to concentric vertical loading, and combined concentric vertical loading and uniaxial unbalanced moment using a plasticity-based nonlinear finite element model (FEM) in Abaqus. The FEM, developed to study the impact of column aspect ratio on punching shear, was calibrated considering seven isolated slab-column specimens. The analysis of isolated slab-wall connections demonstrates that punching failures can occur before one-way shear failures, although the connection capacity is much higher than the expected loads in most structures. Punching shear design methods for interior slab-wall connections subjected to gravity load only, developed from finite element analysis results, are developed and presented in the paper.

This paper reviews the state-of-the-art finite-element analysis (FEA) for reinforced concrete (RC) structures subjected to high-strain-rate deformation and focuses on RC panels subjected to impact loads. Despite extensive experimental studies on the impact behavior of RC panels, a robust concrete material model for accurate simulation of high-strain-rate scenarios is lacking. To address this gap, this study aims to identify the optimal concrete material model for predicting local damage in RC panels impacted by projectiles by simulating the collision of a large commercial aircraft with critical infrastructures, such as nuclear power plants. In this study, the theoretical foundations and parameters of concrete material models were examined to simulate realistically the local responses of RC panels subjected to dynamic loading, specifically focusing on hard projectile impacts at velocities ranging from 100 to 220 m/s (328 to 722 ft/s). Single-element analyses were conducted followed by finite-element simulations of scaled-down aircraft impact tests to assess the ability of the models to predict the failure modes, residual projectile velocities, and damaged areas. Among the four concrete models available in LS-DYNA, the concrete damage model (release 3) provided the best results for the four panels experimentally tested in this study.

Experimental testing of a reinforced concrete shear wall subjected to combined axial load and reverse cyclic lateral displacements was conducted to investigate rocking and sliding observed in a companion wall tested without axial loading, and to assess the effect of axial load on residual drifts. The application of 10% axial load resulted in greater lateral load capacity and stiffness, as well as increased ductility. The presence of axial load contributed to satisfying lower residual drift limits at higher transient drifts. Further analysis was conducted to disaggregate the total lateral displacement into sliding, rocking, shear, and flexure mechanisms. Comparison to the companion wall demonstrated that the present wall had significantly greater contribution from flexural effects with the axial load delaying the influence of rocking until crushing of the concrete. A complementary numerical study of the wall with axial load was conducted, and a modelling methodology was presented to better capture the fracture phenomena of steel reinforcement. This methodology accounted for local fracture of reinforcement and a reduction of reinforcement area due to the presence of strain gauges. The simulation of failure and the predicted lateral displacement capacity were significantly improved compared to a model that did not consider these phenomena.

This paper presents a review of different modeling techniques that have been proposed to employ visual concrete cracking measurements as input in ‘crack-based’ reinforced concrete analysis procedures. The suitability of a recently developed crack-informed modeling approach that incorporates concrete cracking measurements as model input, using an equivalent loading approach where concrete cracks are replaced by fictitious loads that induce similar damage, is examined for applications involving idealized RC panel elements presented in the literature. The procedure employs the formulations of the Disturbed Stress Field Model (DSFM) as the basis for cracked reinforced concrete material and compatibility modeling and a solution framework that permits simple implementation in smeared crack continuum analysis procedures. Preliminary results indicate that crack-based modeling procedures can be used to provide enhanced performance assessments of cracked RC components.

Developed 40 years ago by Frank Vecchio and Michael Collins, the Modified Compression Field Theory (MCFT) and its successor, the Disturbed Stress Field Model (DSFM), have proven to be robust methodologies in modeling the response of concrete structures. Originally developed for newly designed concrete structures, they have been refined over the years to expand their applicability to various engineering problems, including modeling deteriorated and repaired structures. This paper reviews the evolution and application of MCFT in modeling and assessment of deteriorated and repaired concrete structures. The first part focuses on the application of MCFT to advanced field structural assessment, including stochastic analysis procedures that incorporate field data. The second part discusses the evolvement of MCFT to account for two of the most common deterioration mechanisms, reinforcement corrosion and alkali-silica reaction. The last part explores the application of the model to structures repaired with fiber-reinforced polymer composites. It is concluded that the extension of the MCFT formulation has enabled it to reliably predict the behavior of both deteriorated and repaired concrete structures.