Effect of Wall Size on the Rotation Capacity of Reinforced Concrete Structural Walls

Abstract

The limiting deformations of RC members used in seismic design and assessment are mainly based on experimental measurements, for which the lack of structural wall tests of large sizes restricts our knowledge on the deformations of large walls. Thus, experimental studies are compensated by numerical analyses to derive performance-based deformation limits for structural walls. In this study, 2,600 cantilever wall models with a wall length of 2–8 m were analyzed in a parametric study using a verified finite element procedure. The variables were selected as wall boundary-element confinement level and longitudinal reinforcement ratio, wall aspect ratio, axial load ratio, and steel and concrete material strengths. While most models exhibit flexural behavior, a sufficient number of wall models were also included to examine the shear-flexure interaction on walls. Complex localized compressive failure of concrete due to shear-compression interaction at the tip of the compression strut acting diagonally on the web or bending-compression action are the typical localized failure modes that are occasionally encountered in the boundary zones of structural walls. Its size dependence has often been disregarded in the literature for structural walls. This study demonstrates that as the wall length increases, the deformation capacity of structural walls decreases significantly due to localized compressive strains that are amplified by the tension shift effect. Similar to the size effect on strength, a size effect rule on the plastic rotation capacity is proposed. The plastic rotation capacity of structural walls was evaluated in the framework of ASCE/SEI 41. It was found that current damage limits are far from being safe for large walls, and even the response is flexural. Refined plastic rotation limits were proposed for the design and assessment of structural walls.