Ductility of concrete walls: the Canadian seismic design provisions 1984 to 2004

Abstract

The National Building Code of Canada (NBCC) references Canadian Standards Association (CSA) standard A23.3 for the design of concrete structures. The seismic design provisions in the 2004 edition of CSA A23.3, which ensure concrete walls without confinement reinforcement have adequate flexural displacement capacity (ductility), have been completely revised from the provisions in the 1994 edition of CSA A23.3 standard, which are similar to the provisions in the 1984 edition. The new provisions require an estimate of the displacement demand of the seismic force resisting system due to the design earthquake. For ductile walls that are part of a system with good displacement control, the new provisions are less restrictive than the old provisions, while for moderately (nominally) ductile walls, the new provisions are considerably more restrictive than the old provisions. A comprehensive review of the 1984 and 1994 provisions and the background to the 2004 provisions are presented, and it is explained why the seismic design provisions required significant changes.Key words: building codes, concrete walls, displacement-based design, ductility, seismic design.