ABSTRACT
Engineering development and practice goes ahead of both research and the formulation of standards. For this reason, it is inevitable that many structures will be built on the basis of simple ideas and simple rules which cannot be justified when more rigorous design philosophies are introduced. This situation cannot be new, but it presents a considerable challenge to code drafters. A serious problem is found when existing designs which were satisfactory for decades and have a successful safety record are now classed as inadequate.
