Reliability Analysis of Steel Beam-Columns

Probabilistic analyses of the safety of structural members frequently have relied on a formulation of the ultimate limit state equation in which load carrying capacity (resistance) is measured by a single variable R, such as the fully plastic moment for a beam. Safety or reliability is defined by the condition where the effects of the applied loads do not exceed resistance R. However, there is a feeling that alternate formulations in terms of the basic variables that determine resistance, yield stress, section modulus, etc., may be more desirable in certain instances. This note compares measures of reliability calculated from the R-variable and basic variables formulations of the safety problem for hot-rolled steel beam-columns subjected to dead and live loads and considers some of the implications for reliability based design.