International Concrete Abstracts Portal

This article introduces the latest fiber-reinforced polymer panel system developed by the author—SPiRe®+. These panels can serve as formwork, corrosion resistant reinforcement, and waterproofing. With their flat and smooth exterior face and protruding T-profiles on the interior face, the panels act as reinforcing elements for strengthening beams, slabs, and walls.

This is the third article in a five-part series. While Parts 1 and 2 review the procedure and basis for computing deflection of reinforced concrete with a new expression for the effective moment of inertia Ie first adopted in ACI CODE-318-19, this article examines the implications of this change for satisfying deflection limits of beams and one- and two-way slabs. A need is seen to revise current minimum thickness values for beams.

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.

Punching shear failure of RC flat slab connections cause loss of slab’s supports. The detached slab is falling and impacting the slab below. That problem requires thorough investigation and appropriate design guidelines. This paper presents research results on various aspects of this impact scenario. The analysis is based on an advanced numerical model that has been formulated, and the impact analyses follow the damage evolution in the concrete and reinforcement until complete connections failure of the impacted slab is developed, and a progressive collapse scenario starts. The effects of slab geometry and material properties were examined, and the contribution of special shear reinforcement and integrity rebars were investigated. The potential contribution of added drop panels to enhance slab resistance were examined. The slabs impact effect on the supporting columns has been investigated as well. The suitability of current static loading design-criteria to provide safe design against dynamic/impact punching shear is assessed. It shows that the current static-loading based design standards cannot ensure resilience of flat slab connections to impact loading and therefore cannot prevent a progressive collapse scenario. Analyses results are compared with inspected failure details of a collapsed RC flat slabs parking garage building, and excellent agreement is obtained.