International Concrete Abstracts Portal

This Symposium Volume reports on the latest advancements related to the various facets of modeling and performance assessment of concrete structures. The volume contains 10 papers that were presented at the ACI Convention held in Toronto on April 1st, 2025. The symposium was dedicated to celebrate Prof. Frank J. Vecchio’s extraordinary research contributions and accomplishments in the development of behavioral models and analytical tools for the assessment of concrete structures. The papers cover different aspects related to modeling and performance assessment of concrete structures including developments of the Modified Compression Field Theory, finite element modeling of punching shear in slabs, behavior and modeling of steel fiber reinforced concrete members subjected to torsion, modeling of concrete structures subjected to impact loading, behavior and modeling of slender walls, modeling of concrete frame elements, behavior and modeling of GFRP reinforced members, crack-based assessment of concrete structures, and advancements in modeling deterioration mechanisms and repaired concrete structures. Sincere acknowledgements are extended to all authors, speakers and reviewers as well as to ACI staff for making this symposium a success. Anca-Cristina Ferche, Editor Vahid Sadeghian, Editor

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.

Current nonlinear modeling software for concrete frames typically employs line elements with plastic hinges defined at user-selected locations. While this is a simple and computationally efficient approach, a number of drawbacks limit its application. They include the challenges with defining the interacting shear and moment hinge curves, uncertainties with hinge locations and lengths, and difficulties in capturing the post-peak response. Two-dimensional continuum methods address these limitations, but their computational cost limits their applicability. This study presents an alternative modeling method, and associated computer software, with the objective of combining the simplicity of frame elements with the accuracy and result visualization capabilities of continuum methods. The method, developed in the last two decades, employs a distributed-plasticity, layered-section approach based on the Disturbed Stress Field Model (DSFM). The distributed-plasticity approach eliminates the need for defining plastic hinges while the DSFM enables capturing the shear, moment, and axial force interaction. The total-load and secant-stiffness formulation provides numerically stable solutions, even in the post-peak region. This paper presents an overview of the theoretical approach, unique aspects, and capabilities of this method. The validation studies undertaken for 148 experimental specimens, subjected to static (monotonic and cyclic) and dynamic (impact, blast, and seismic) load conditions, are also presented.

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.

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.