Author(s)

M. Holický

Abstract

Design working life and target reliability levels recommended in various national and international documents are inconsistent. Indicative values of design working life are within a range from 10 to 100 years for different types of structures, recommended target reliability indexes are usually given for one or two reference periods (1 year and 50 years), without an explicit link to the design working life. The contribution attempts to clarify the relationship between the design working life and the reliability index and to provide guidance for specification of the target reliability level for given consequences, designs working life and discount rate. The theoretical study based on probabilistic optimization is supplemented by practical recommendations. It appears that the optimum reliability indexes depend primarily on the ratio of cost of structural failure (malfunctioning costs) and the cost per unit of structural parameter, less significantly on the design working life and discount rate. Keywords: design working life, target reliability, optimisation. 1 Introduction Design working life is understood as an assumed period of time for which a structure is to be used for its intended purpose without any major repair being necessary. Indicative values of design working life (10 to 100 years for different types of structures) are given in EN 1990 [1]. Recommended target reliability indexes are given for two reference periods (1 year and 50 years), without any explicit link to the design working life (see Table 1). It should be underlined that a couple of  values (for 1 year and 50 years) given in Table 1 for each reliability class corresponds to the same reliability level. Practical application of these values, however, depends on the time period considered in the verification, which may be linked to available probabilistic

Keywords

design working life, target reliability, optimisation