The Analysis of Structural Safety

The work of the Task Committee on Factors of Safety, ASCE, to date (as of 1965) is summarized with a brief review of the work that has been done elsewhere in the field of structural reliability. On the basis of the assumption that the resisting strength of and the load applied to a structure are usually random variables, the probability of failure and reliability function are introduced as possible measures of structural safety, and related to the conventional safety factor. Reliability functions of structures consisting of multiple members are derived for the cases when the loads are applied at equal intervals or at prescribed instants and where the number of occurrences of the load is governed by a Poisson law, assuming that the resistance of the structure is either deterministic or random. Two numerical examples dealing with safety of a transmission tower and of an aircraft wing are presented to illustrate the proposed method of evaluation of structural safety.