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

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.

The limited availability of research studies related to the behavior of Steel Fiber Reinforced Concrete (SFRC) members subjected to torsion has hindered the development of clear and reliable design guidelines. Recent efforts by various researchers have been devoted to the development of analytical models for predicting the torsional response of SFRC members, supported by experimental results which have highlighted the efficiency of steel fibers in improving the torsional resistance and stiffness. For beams subjected to moderate or low levels of torsion, steel fibers, even at moderate dosages, have demonstrated the potential to replace minimum conventional torsion reinforcement, thus providing significant advantages for practical applications. This paper presents a discussion of the recent developments in research related to testing SFRC members under pure torsion. A comprehensive database of experimental test data is collated to provide a state-of-the-art in this respect. Additionally, the manuscript delves into analytical prediction models for the torsional capacity by some European code-oriented models, recently introduced by the Eurocode 2 as well as by the Authors of this paper. The results of model predictions are compared with available experimental data to assess the effectiveness and reliability of the models.

The modified compression field theory (MCFT) is a general model for the behavior of diagonally cracked reinforced concrete. When applied to beams and columns, a number of very significant simplifications can be made to make it easier to apply in practice for day-to-day design and strength assessment. While the methods used to generate the simplified MCFT have been explained in previous papers, the actual historical and technical process that led to the work was somewhat different than the technical arguments made in the previous publications. This paper explains the procedures that actually occurred in 1999 to 2002 to generate the equations of the simplified MCFT for members with stirrups. The process shows the importance of working backwards from solutions and engineering intuition in the generation of technical theories. While the analysis method ended up being practical and technically sound, its creation was a people-based process and learning about it can hopefully be helpful to future researchers who want to know how “it really happened”.

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.