Robustness of Structures: theoretical framework

An important aspect of the COST Action TU0601 “Robustness of structures” concerns the development of a theoretically sound basis for the assessment of robustness and acceptance criteria for structural robustness which can form the basis for development of practical relevant methods for ensuring robust design as well as strategies for maintaining the robustness of existing structures throughout their service life. This paper describes an overall theoretical framework for assessing robustness of structures developed within WG1 “Robustness of structures”.

Robustness can be defined in different ways and on different levels of complexity / applicability. On the most general level robustness is assessed taking basis in decision analysis theory by estimating both direct risk, which is associated with the direct consequences of potential damages to the structure, and indirect risk, which corresponds to the increased risk of a damaged structure. Indirect risk can be interpreted as risk from consequences disproportionate to the cause of the damage. Robustness of a structure can therefore be measured by the contribution of the indirect risks to the total risk.

The risk-based approach for implementation for robustness is described and different measures of robustness are described and discussed – a risk-based, a reliability-based and a deterministic measure. These measures require probabilistic models to be formulated for the important failure modes and the uncertain parameters related to loads, strengths and models. Further, for quantification of the risk-based measure of robustness, modeling of the consequences of failures is needed. These probabilistic and consequence models are in general difficult to establish and not directly applicable for recommendations for practical applications. But the risk and reliability based robustness measures can be used as a rational basis for formulating recommendations for practice.