Performance-Based Optimization of Passive and Active Fire Protection for the Resilience of Concrete Tunnel Liners to Vehicular Fires

Abstract Several technologies such as forced ventilation, active fire-fighting systems, and passive fire protection systems are used in current practice to mitigate fire-induced structural damage to concrete liners in roadway tunnels. This paper outlines a new decision-making approach to optimize these strategies by weighing their initial investment and life cycle costs against their relative impact for enhancing the tunnel’s resilience to fire (quantified in terms of post-fire downtime and cost as a function of the severity of fire-induced damage). First, a concrete liner damage assessment tool is developed to account for the presence or lack of active and passive fire protection, as well as realistic uncertainties in the thermal properties of the materials used. Second, both the cost of protection and the potential economic loss due to stochastic vehicle fire hazards are quantified for a single mitigation strategy or a combination of strategies. The economic losses include the direct repair cost and the functionality loss and detour distance due to the duration of tunnel closure, which is determined as a function of concrete liner damage severity and the corresponding repair procedures. Third, a genetic algorithm is used to perform a multi-objective optimization, resulting in a Pareto front as the reference for the decision-making process. The objectives and constraints of the algorithm can be readily modified based on practical engineering requirements. The proposed approach is then used to evaluate the sensitivity of fire protection selection to tunnel geometry, traffic volume and composition, and detour distance during closure.