The design, analysis, and performance of structural concrete slabs under punching shear loading conditions are topics that have been studied extensively over many decades and are well documented in the literature. However, the majority of the work reported in these areas is generally related to conventional concrete slabs subjected to highly idealized loading conditions. Structural engineers need to find new, innovative ways and methods to design new structures but also to strengthen existing infrastructure to ensure safety, resilience, and sustainability. These challenges can be addressed through the use of integrated systems and high-performance technologically advanced materials. We live in a new era of improved computational capabilities, advances in high-performance computing, numerical and experimental methods, and data-driven techniques, which give us broader access to larger and better data sets and analysis tools. These new advancements are essential to develop deeper insights into the structural behavior of concrete slabs under punching shear and to implement and analyze new materials and loading conditions. This Special Publication presents recent punching shear research and insights relating to topics that have historically received less attention in the literature and/or are absent from existing codified design procedures. Topics addressed include: the usage and impacts of alternative/modern construction materials (new concrete and concrete-like materials, nonmetallic reinforcement systems, and combinations thereof) on slab punching shear resistance, novel shear reinforcement or strengthening systems, the influence of highly irregular/nonuniform loading and support conditions on slab punching shear, impact loading, new design and analysis techniques, and the study of the punching shear behavior of footings. This Special Publication will be of interest to designers who are often faced with punching-related design requirements that fall outside of traditional research areas and existing code provisions, as well as for researchers who are performing research in related areas. Perspectives from a broad and international group of authors are included in this Special Publication, relating to a variety of punching-related problems that occur in research and practice. In particular, researchers from the United States, Canada, Ecuador, the Netherlands, Italy, Brazil, Israel, Portugal, Spain, the United Arab Emirates, and Germany contributed to the articles in this Special Publications. To exchange views on the new materials, tests, and analysis methods related to punching, Joint ASCE-ACI Committee 421, “Design of Reinforced Concrete Slabs;” Joint ASCE-ACI Committee 445, “Shear and Torsion;” and subcommittee ACI 445-C, “Punching Shear,” organized two sessions titled “Punching shear of concrete slabs: insights from new materials, tests, and analysis methods” at the ACI Spring Convention 2023 in San Francisco, CA. This Special Publication contains several technical papers from experts who presented their work at these sessions, in addition to papers submitted for publication only. Co-editors Dr. Katerina Genikomsou, Dr. Trevor Hrynyk, and Dr. Eva Lantsoght are grateful for the contributions of the authors and sincerely value the time and effort of the authors in preparing the papers in this volume, as well as of the reviewers of the manuscripts. Aikaterini Genikomsou, Trevor Hrynyk, and Eva Lantsoght Co-editors

This paper presents the application of a low-cost thick-shell nonlinear finite element analysis (NLFEA) procedure to estimate the punching shear resisting performance of reinforced concrete slab-column connections under variable connection shear stress conditions. Variation of connection stress conditions stems from columns with different cross section aspect ratios, different distributions of gravity loading conditions, and slabs constructed with significantly different planar reinforcement conditions in the orthogonal directions. In this regard, thirty-five isolated slab-column connection specimens presented in the literature were analyzed using a shell finite element-based analysis procedure and the results from these analyses were used to assess NLFEA model performance. All results were developed using a predefined set of material models and analysis parameters, defined on the basis of prior and unrelated validation studies, and were shown to provide good agreement with experimental findings without the need for calibration studies or the adoption of case-specific failure criteria. From the findings obtained, it was determined that the thick-shell NLFEA employed is suitable for estimating the punching shear response for slabs subjected to varied and highly non-uniform shear stresses within the connection regions and provided similar levels of precisions as that previously obtained for isolated slab-column connections constructed with idealized geometries and reinforcing conditions, subjected to idealized loading conditions.

Significant research efforts have been devoted to achieving high performance of slab – column connections subjected to lateral loading. Solutions such as using stirrups and headed studs have been shown to work well. With the development of concrete materials with enhanced properties, new possibilities have arisen to employ solutions that are easy to apply and cause less congestion of reinforcement. A total of nine tests on flat slab specimens subjected to combined gravity and lateral loading are discussed, including two new specimens with High Performance Fiber Reinforced Concrete (HPFRC) over a limited region near the column. The main experimental variables were the flexural reinforcement ratio and the punching shear improvement method: none, headed studs, High Strength Concrete (HSC) or HPFRC. It is shown that excellent behavior is achieved with a relatively small amount of HPFRC, extended up to 1.5 times the effective depth of the slab from the face of the column. Punching was completely avoided until the end of the loading protocol (6% drift) for the specimens with HPFRC, whereas reference specimens without punching shear reinforcement failed at 1% drift and specimens with HSC reached 3% drifts. Additionally, the use of HPFRC led to an increased unbalanced moment transfer capacity and lateral stiffness, though this effect was more pronounced for specimens with lower flexural reinforcement ratio.

Several studies have shown the superiority of concrete-filled FRP tubes (CFFTs) over conventional reinforced concrete columns. These observations indicated that CFFT columns exhibit much better static structural performance (in terms of ductility and load-carrying capacity). However, up to date, very few studies have considered the behavior of CFFT columns under dynamic impact loading. This paper presents a numerical study to investigate the impact resistance of columns strengthened with glass FRP tubes. LS-DYNA finite element software is used to investigate CFFT and RC columns subject to lateral impact loading induced by a 221 kg pendulum. The columns are 1800 mm with the fixed support at the base and 152 mm internal diameter. The models are designed to simulate the destructive effects of a vehicle collision into bridge piers. The impact forces and deformation states are analyzed. The impact behavior of CFFT columns is also compared with the conventional RC columns counterparts. The numerical results showed that the CFFT columns had higher dynamic impact load and less lateral deflection compared with the RC counterparts. The impact resistance of the CFFT columns was enhanced with an increase in the FRP tube thickness.

This paper investigates the use of glass fiber reinforced polymer (GFRP) bars to reinforce the jointed precast bridge deck slabs built integrally with steel I-girders. In addition to a cast-in-place slab, three full-size, GFRPreinforced, precast concrete slabs were erected to perform static and fatigue tests under a truck wheel load. Each slab had 200 mm (7.9 in) thickness, 2500 mm (98.4 in) width normal to traffic, and 3500 mm (137.8 in) length in the direction of traffic and was supported over a braced twin-steel girder system. The closure strip between connected precast slabs has a width of 125 mm (4.9 in) with a vertical shear key, filled with ultra-high-performance concrete (UHPC). Sand-coated GFRP bars in the precast slab project into the closure strip with a headed end to provide a 100 mm (3.9 in) embedment length. A static test and two fatigue tests were performed, namely: (i) accelerated variable amplitude cyclic loading and (ii) constant amplitude cyclic loading, followed by static loading to collapse. Test results demonstrated excellent fatigue performance of the developed closure strip details, with the ultimate load-carrying capacity of the slab far greater than the demand. While the failure in the cast-in-place slab was purely punching shear, the failure mode in the jointed precast slabs was punching shear failure with incomplete cone-shape peroration through the UHPC closure strip, combined with a major transverse flexural crack in the UHPC strip. This may be attributed to the fact that the UHPC joint diverted the load distribution pattern towards a flexural mode in the UHPC strip itself close to failure.