Uncertainties Associated with Tunnel Design Fire Scenarios

Computer fire modelling and design fire scenarios are traditionally used in the tunnel design process to challenge tunnel systems, e.g. smoke ventilation, evacuation routes and strategy, and the exposure of structural members. In general, any such fire scenario should be reasonably severe, however, not unrealistically, which may lead to unnecessary over-designing and cost increase. This approach is commonly referred to as the worst-case design fire approach. The objective of the paper is to analyze the impact of uncertainties associated with input data and design fire selection on the representativeness of the design fire scenario. Firstly, the design fire scenario specifications are mapped and uncertainties relating to input data identified and quantified. Subsequently, a risk-based design fire selection approach is introduced taking into account the objective of the analysis: life safety or property protection. The paper is concluded with recommendations regarding the significance of selected input parameters, given analysis objectives, and the possibilities of their uncertainty treatment.