ABSTRACT
This paper describes the assessment of the cost efficiency of risk mitigation measures for terrorist attacks with Improvised Explosive Devices (IEDs) for an iconic bridge structure. The assessment is performed with a decision theoretical framework building upon very recent advances in the framework of the COST Action TU1402 on Quantifying the Value of Structural Heath Monitoring. The decision scenario is formulated for a decision maker constituting an authority responsible for the societal safety of the infrastructure and consequently the direct risks for the infrastructure owner and the indirect risk due to fatalities and importance of the infrastructure are considered. The mitigation strategies are classified within the decision theoretical context as protection measures, which may be implemented in the design phase of a bridge, and as control, i.e. information acquirement, strategies. The identification of efficient measures for risk mitigation is based on (1) the risk and expected cost based optimization of actions and information and their combination before implementation, (2) on quantifying and assuring significance in risk reduction and (3) on the quantification of the uncertainties associated to the implementation. These criteria ensure a transparent decision and the performance of the measures before strategy implementation. It is found that the decision is relying on the identification of the threat level and that control strategies may be in favor as their costs are adjustable. However, for very high threat levels, bridge protection strategies or protection strategies in combination with control strategies may be more cost efficient.
