A database for investigating NZS3101 structural wall provisions

Abstract

During the 2010/2011 Canterbury Earthquakes several reinforced concrete (RC) walls in modern buildings with ductile detailing performed poorly and exhibited unexpected failure modes (e.g., local buckling of longitudinal reinforcement and global buckling of the wall section out-of-plane). These observations led to a number of revisions to NZS3101:2006 (A2) related to minimum reinforcement, transverse reinforcement ties, and axial load limitations. Due to the urgent need to make these changes despite the lack of availability of a comprehensive study to provide guidance, these amendments were not always verified with a robust set of experimental results. This paper summarises and assesses a number of these amendments through a newly created database that focuses on ductile, rectangular walls with particular attention paid to end region detailing, axial load conditions, and the response to uni-axial, reversed-cyclic, pseudo-static loading. Based on analyses conducted using the database, a reduced bar slenderness ratio (defined as the ratio of unsupported bar length to bar diameter) of 5 is recommended for walls with low axial loads (<0.1Agf’c), and a minimum transverse reinforcement ratio of 0.4% in the end region is suggested to reduce the likelihood of concrete crushing in walls designed with a limited ductile or ductile plastic hinge region. Preliminary assessment of the influence of confinement depth and web anti-buckling ties on the ultimate state behaviour of walls indicates that additional research is required on these topics.