Dynamic analysis of tall RC shear walls designed with light reinforcement contents

Analyses of tall reinforced concrete (RC) shear walls subjected to earthquake excitation highlight the amplified dynamic moments that occur at the wall mid-height due to higher mode responses, as the cracking damages were observed at both base and upper region for tall RC shear walls in past shaking table tests. Such amplified moment demands may result in unexpected reinforcement yielding outside of the intended plastic hinge region and impact on the termination rules for longitudinal reinforcement contents within the upper portion of RC shear walls. The aim of this study was to investigate the dynamic response of tall RC shear walls designed with minimum longitudinal reinforcing contents. A fibre model scheme was developed and validated against prior test results to ensure accuracy in calculating the dynamic responses. Material regularisation techniques were adopted to ensure an objective calculation for both global and local response parameters. A series of parametric analyses were then conducted to investigate several key aspects of the dynamic response of lightly reinforced walls, including the impact of a high cracking moment, ground motion types, comparisons between dynamic and pushover responses, influence of high concrete tensile strengths, the reinforcement contents in the upper stories, and the magnitude of axial load. The analyses also investigated the curtailment height of longitudinal reinforcement for key design scenarios. The dynamic analyses conducted showed no evidence of highly concentrated strains in the upper portion of the walls modelled, resulting in a low risk of premature fracture of reinforcement in the upper stories of lightly reinforced tall walls. In addition, the longitudinal reinforcement termination requirements stipulated in the current design provisions were found insufficient to restrict the peak reinforcement strain within the detailed plastic hinge region. In order to prevent the unexpected inelastic failure with the peak reinforcement strains in the non-detailed upper region rather than at the detailed wall base, the revised longitudinal reinforcement termination rule was proposed for the regions above the plastic hinge to ensure satisfactory seismic performance.