12 - Reliability of aged land-based structures

Abstract

This chapter outlines procedures for the estimation of the reliability of land-based structures as they deteriorate with time, such as resulting from fatigue and corrosion, including depth of pitting. Many forms of deterioration are influenced by environmental conditions. Materials of interest include structural steels, reinforced and pre-stressed concretes, masonry and stone, timber and, to a small extent, various fibre-reinforced plastics. Typically the likely ’design life’ is of interest. As most structures consist of multiple components (or members) interaction between members must be considered, although many structures can be idealized as ’series’ systems. The theory for this is outlined and solution techniques such as Monte Carlo analysis and importance sampling are also outlined. This includes situations with multiple loading systems, for which extreme value representations for loads are not appropriate since the occurrence of the maximum of one load is unlikely to coincide with the occurrence of the maximum of another load. The so-called Turkstra’s rule is a convenient but simplified approach in this case. When the resistance of the structural system is time-dependent, and more than one stochastic load is applied, outcrossing theory must be applied and the ’outcrossing rate’ ν(t) estimated. This may be a function of time and thus enable consideration of deteriorating structural systems. Some recent efforts for this in the literature are reviewed.