Hybrid Simulation Testing of Normal and High-Strength RC Shear Walls in Nuclear Facilities under Ground Motion Sequences

Abstract

Reinforced concrete (RC) shear walls are widely used as a seismic force–resisting system in nuclear facilities. Such walls are designed to be relatively thick with a few openings for radiation shielding as well as for blast and fire protection. These geometrical requirements typically result in low-aspect-ratio walls with high reinforcement ratios that are provided by two or more mats, leading to complex construction activities and high construction costs. The use of high-strength reinforcement (HSR) has the potential to address such constructability and economic issues by reducing the required steel areas and rebar congestion. However, because relevant nuclear design standards restrict the use of HSR in their safety-related structures, most previous experimental studies to date focused on investigating the seismic performance of nuclear low-aspect-ratio RC shear walls when only normal-strength reinforcement (NSR) was used. To tackle this knowledge gap, the current study utilizes the pseudodynamic hybrid simulation testing technique to experimentally compare the performance of nuclear low-aspect-ratio RC shear walls with HSR and NSR when subjected to ground motion sequences. In this respect, two RC shear walls (i.e., W1-NSR and W2-HSR) with an aspect ratio of 0.83 were tested, where both walls were designed to have a similar lateral strength; however, Wall W2-HSR had a reduced reinforcement ratio of 1.23% compared with Wall W1-NSR, which had a reinforcement ratio of 2.20%. The two walls were subjected to several ground motion records to investigate their force-displacement responses, lateral strengths, ductility, stiffnesses, deformation capacities, cracking patterns, rebar strains, and failure modes. A numerical model was then developed and experimentally validated to simulate the response of the two test walls under such ground motion records. The results show that both walls achieved similar ultimate strength values; however, relevant nuclear design standards were not able to accurately estimate these values for Wall W2-HSR. In addition, although Wall W2-HSR had wider cracks relative to Wall W1-NSR during all ground motion sequences, the former wall achieved a high displacement ductility value without any premature brittle shear failure. The experimental results presented in the current study are expected to facilitate the adoption of HSR in low-aspect-ratio RC shear walls within nuclear construction practice.