ABSTRACT
The limitations of elastic structural theory with respect to the assessment of actual resistance, hence of safety, have long been recognized. Indeed, to accept as valid the elastic behaviour up to the critical point of the structure is equivalent to identifying the crisis with the first attainment of a critical stress condition in any point of the structure, i.e. to assuming a weakest-link type of behaviour (cf. Section 1.5). This is in practice true in some cases, such as statically determinate structures or structures made of brittle material, but in most structures a stress redistribution allows the loads to grow further beyond the level corresponding to the first critical condition.
