International Concrete Abstracts Portal

Nuclear power plants use reinforced concrete shear walls with flanges for lateral load-resisting systems. The present study investigated the shear–friction strength of reinforced concrete walls with flanges by testing eight wall specimens under cyclic lateral loading. The test parameters were the flange length, flange configuration, wall thickness, interface roughness, and load direction. The test results showed that vertical reinforcing bars in the flanges, as well as the web, increased the shear–friction strength of the walls. However, due to the premature punching failure at the web–flange joint, the contribution of the thin flange was limited. Further, the shear–friction strength of the symmetric flanged wall was identical, regardless of the load direction: the shear–friction strength of the flanged wall was determined by the overall vertical reinforcing bars placed in the web and flange. The tested shear–friction strengths, including previous test results, were compared with the predictions of current design methods. Including the flange contribution in the current design methods improved the prediction of test results compared to the case that neglects the flange contribution.

Slabs-on-ground supporting storage racks are often subjected to concentrated uplift under building code seismic forces. While methods for determining slab-on-ground capacity for downward loads are well defined, guidance for resistance to uplift has been limited and relies on finite element analysis. A simplified approach is presented for calculating slab-on-ground uplift capacity as a function of slab thickness, reinforcing content, and storage rack frame depth. Testing is conducted on small-scale concrete samples in bending to obtain the material properties. Model slabs are created and tested for an upward and downward force couple representing concentrated seismic uplift on a reinforced slab-on-ground. The plastic hinge failure mechanism of the slab samples is correlated with finite element models, and straightforward formulas are developed to produce a table of uplift capacities for common storage rack and slab-on-ground configurations.

Prefabricated structural wall buildings exhibit superior strength, stiffness, and ductility under seismic loading effects. Segmental wall construction is popular due to easy transportation and on-site assembly. The present study deals with the performance of precast wall elements connected through welded plates vertically subjected to the seismic loading conditions. The study proposes welded plates with varying thickness to connect two structural walls on one or both faces. Full-scale quasi-static load tests have been performed to analyze the seismic behavior of the connections. The conventional foundation with loading beams at top and bottom, to test the structural walls, was replaced with a special steel shoe set-up, achieving the real conditions, to minimize the testing cost. It has been observed that the connections using mild steel plates achieve the most desirable characteristics, like plate yielding, energy dissipation, and ductility. High-strength steel plates fail in brittle mode with poor post-peak response, indicating precautions in selecting the type of connecting steel plates in precast construction. The proposed connecting plates improve the ductility and post-peak response for easy retrofitting of the precast wall system. The study brings out improvement in the seismic performance, selection of materials, and connection detailing for resilient precast structures.

This study introduces a new anchorage strategy using ultra-high-performance concrete (UHPC) to attach unbonded post-tensioning (PT) strands to existing foundations. This solution complements a seismic retrofit scheme investigated by the authors, which transforms non-ductile cast-in-place reinforced concrete (RC) shear walls into unbonded post-tensioned rocking shear walls, following concepts of selective weakening and self-centering. In the proposed PT anchorage scheme, mild steel reinforcements are inserted through the shear wall thickness and into the foundation. Subsequently, UHPC is cast around the wall base, forming a vertical extension connected to the foundation, which is used to anchor the unbonded PT strands. The feasibility and performance of the anchorage scheme were investigated through a combination of laboratory testing and numerical simulations. Pull-out testing on four scaled-down anchorage specimens was conducted in the laboratory. Hairline cracks were observed in the UHPC during testing. Additionally, 3D finite element (FE) models were created, validated, and used to study the performance of the proposed anchorage scheme under lateral loading. The simulation results support the effectiveness of the proposed anchorage strategy.

This research establishes a systematic methodology for selecting a migratory corrosion inhibitor (M-CoI) as a repair strategy for reinforced concrete structures exposed to aggressive environments. Conducted in two phases, Phase 1 involves corrosion testing in pore solutions to evaluate inhibitor efficacy, while Phase 2 examines the percolation ability of M-CoIs in different concrete systems and the performance of M-CoI in RC with corroded reinforcing bars. The findings reveal that the efficiency of the compounds as repair measures is significantly lower than their preventive performance, primarily due to the presence of corrosion products on the steel surface. Additionally, the effectiveness of the M-CoIs is influenced by their concentration and form at the reinforcing bar level; specifically, 4-Aminobenzoic acid (ABA) achieved maximum concentration in its purest form, whereas Salicylaldehyde (SA) and 2-Aminopyridine (AP) reached the reinforcing bar in lower concentrations. Importantly, the study highlights that compounds effective in pore solution may not perform well in concrete, underscoring the necessity of considering the intended application, preventive or repair, when selecting inhibitors. Thus, a comprehensive approach involving both pore solution testing and migration ability assessments is essential for optimal corrosion protection in reinforced concrete.