Discussion: Seismic loading provision changes in National Building Code of Canada 1985

Abstract

Barring the section on torsional effects and dynamic analysis, this paper practically repeats what was given in an earlier paper (Heidebrecht et al. 1983), that paper having been discussed by Ferahian (1985), albeit as printed it was only part of my original response. The Seismic Zoning Map of Canada of the National Building Code of Canada (NBCC) 1970, though based on the MilneDavenport (1969) study, did not appear as such in that paper as the authors appear to imply (p. 654). As described elsewhere (Ferahian 1970), this map was developed after the evaluation, among others, of additional comparative studies done by Dr. Milne using his computer program for extreme-value statistics applied to both modern (since 1899) and historic (since 1638) Canadian seismic samples as well as Californian samples. The resultant map was approved by the Canadian National Committee on Earthquake Engineering but its format was accepted as presented to that Committee. As indicated elsewhere (Ferahian 1985), for building code purposes, such detailed seismic contours as are given in the authors' Figs. 1 and 2 are not warranted within the confidence limits inherent in our seismic sample and the methodology utilized in translating the historic seismic data into engineering design data. And this is especially so for such sparsely populated areas of Canada as the Northwest Territories and the Yukon. But then, all of Canada was sparsely populated and our historic seismic sample with any semblance of records does not predate the beginning of the 17th century. For these initial historic records, we have to thank the Jesuit's Relations, but then, these records are, relatively speaking, no more than mere specks on this vast land.