Commentary on the basic philosophy and recent development of safety margins

Abstract

The principal effects influencing safety margins are recapitulated. Human errors are found to be the major source of structural failure. A revised format for safety margins is proposed, using partial factors, one of which should represent the effects of human errors. It should be used as a basic safety margin, reflecting the fact of the importance of human errors.Recent changes in design rules as set forth in the National Building Code of Canada 1975, are discussed and criticized for having reduced effective safety margins to unacceptably low levels. Examples are given to illustrate possible consequences of the use of such low safety margins.