ABSTRACT
ABSTRACT: Life-cycle cost (LCC) criteria hold important implications for the optimal design of structural components and systems. While a broad range of component designs, for instance, may satisfy local standards, the influence of environmental factors on structural deterioration – among other things – can cause wide variations in corresponding service life and related LCC forecasts. In order to select the ‘best’ design, therefore, engineers must: (a) select a satisfactory and defensible measure of deterioration, (b) link that measure to a LCC model, and (c) account explicitly for the uncertainty that naturally surrounds such complex problems resting on forecasts over often very long time periods. The authors of this paper elucidate a method of LCC analysis intended to satisfy these requirements and illustrate its implementation through a straight-forward case study. Subject to local standards, a range of steel-reinforced concrete beam designs are analyzed in the context of environmental exposure (including application of de-icing salts) typical of the Canadian prairies. Structural deterioration is measured in terms of bending moment capacity and related implications for safe use. Uncertainty is handled through an efficient, stepwise application of deterministic, sensitivity and risk analyses that leads naturally to stochastic characterization of demonstrably influential sources of uncertainty. This permits the derivation of time-varying structural reliability estimates that ultimately affect service life and related LCC forecasts. The results of the study demonstrate the sometimes surprising implications of LCC criteria for the practice of engineering design.
