Traffic-based quantitative risk analysis of structural fire damage to roadway tunnel linings

Abstract

This paper demonstrates a quantitative risk analysis (QRA) approach of fire-induced damage to the reinforced concrete linings in roadway tunnels. Large fire events associated with buses and heavy goods vehicles are the focus of this study because their impact on the tunnel linings is structurally significant versus fires from smaller vehicles. The proposed approach accounts for stochastic variations of fire severity and frequency (based on traffic volume and the percentage breakdown by vehicle type) as well as the consequences (structural and economic) of thermal exposure to tunnel linings. The probabilistic distribution of fire size is developed using available weight-in-motion data, and combustible vehicle mass is correlated with the peak heat release rate using published test data and forensic reports. The heat transfer from the vehicle fire to the tunnel linings was modelled by a fast-running computational tool that was previously developed by the authors. Fire-induced damage to the tunnel linings is categorized into three levels of progressive strength reduction and cracking potential. Economic impacts are calculated in terms of estimated repair costs. The proposed approach enables informed decision making for the design or renovation of tunnel fire protection by quantifying the loss potential for severe fire hazards in a given tunnel.