ABSTRACT
For a long time, life-cycle optimization has been recognized as an implicit and essential objective of engineering design, construction and maintenance actions. For the establishment of recommended practical criteria and methods for the achievement of that objective, it is necessary to adopt a formal decision framework, based on the identification and evaluation of an adequate set of quantitative indicators to describe the performance of a given system. In general, this description will be strongly affected by significant uncertainties, associated with a) the random variability of the times and intensities of future excitations and of the mechanical properties of the system, b) our imperfect knowledge about these concepts, and c) the limitations of the mathematical models used to represent them. This leads to the adoption of a probabilistic framework to describe the expected performance of a system; it should be capable of dealing with two types of uncertainties: random or aleatory (group a, above) and epistemic (groups b and c). In earthquake engineering problems, the excitations include the gravitational loads (dead and live) and the seismic events. The expected performance of a system when subjected to any of those events depends on both the intensity of the latter and the mechanical properties of the former, which depend in turn on the level and distribution of damage that may have accumulated as a consequence of the system’s response to previous seismic events or of the action of any other agent, such as differential settlements due to gravitational loads.
