International Concrete Abstracts Portal

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.

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.

Should concrete core samples extracted from a structure be submerged in water until testing? This month’s Q&A provides answer to that question along with a discussion on proper and improper moisture conditioning of cores to be tested per ASTM C42/C42M.

Reinforced concrete sections have typically been the most used material for hardened protective construction due to their mass and the ductility provided by the reinforcement. The additional mass of these sections reduces deflections and increases dampening, which reduces vibrations. Even for the occasional occurrence of hardened steel structures, the foundation is comprised of reinforced concrete. Reinforced concrete structures are hardened for a multitude of reasons. Some of the most common include antiterrorism, force protection, equivalent protection for quantity distance arc violations, personnel protection, prevention of prompt propagation, asset protection, and elastic response during repeated detonations. Many of the structures used in the Department of Defense (DoD), for these purposes, were built in the United States (US) during the World War II era (1941-1945) for a rapid increase in production and storage of explosives. This puts the average age of many of these facilities at close to 80 years-old, which is past their originally intended service life. This paper presents a structural health and visual inspection technique developed by the U.S. Army Corps of Engineers (USACE) Engineering and Support Center Huntsville (CEHNC) Facilities Explosives Safety Mandatory Center of Expertise (FES MCX) and the Engineering Research and Development Center (ERDC) Geotechnical and Structures Laboratory (GSL) for the inspection of reinforced concrete earth covered magazines (ECMs) [9]. This inspection process has been utilized to inspect over 1500 earth covered magazines across multiple countries over the last decade and aid DoD installations in planning and budgeting for concrete repairs and ECM replacements. The CEHNC FES MCX partners with ERDC for concrete coring and testing of samples to determine the estimated remaining service life of concrete structures based on the carbonation front of cored samples determined by the carbonation tests in relationship to the steel reinforcement. Examples of historical application will be given, and details provided on how these methods can lead to improved life-cycle cost and decision making.