Yield displacement of slender cantilever RC walls as a function of the seismic demand features

Abstract

The yield displacement is a relevant parameter to design slender cantilever RC walls under seismic actions. If the wall is expected to undergo inelastic excursions, then the yield displacement is used to estimate ductility demands, which are in turn used to design boundary elements (confinement reinforcing). In the last years, expressions to estimate the yield displacement have been proposed in several studies; many of them resorting to models with concentrated inelasticity. Results obtained with these models could be unrepresentative of the phenomenon studied, due to the assumption that the wall has elastic behaviour and constant stiffness above the critical section; evidence shows that the flexural stiffness of a wall varies during the dynamic response. Independently of the model used, most of the studies consider pushover analysis with different lateral load patterns (e.g. triangular or uniform), assuming the nature of the seismic demand. In this work, a parametric study of the yield displacement for cantilever slender RC walls is presented. The results were obtained from nonlinear response history analyses (NRHA) for a set of cantilever RC walls, representative of real wall buildings. To carry out NRHA, natural and artificial records with different features are used. Additionally, walls with different aspect ratio, height, thickness and longitudinal reinforcement are considered; walls were modelled with unidirectional fibres. The final discussion is focused on the influence of the higher mode effects in the yield displacement and its variability, in order to provide useful and simple design recommendations.