Structural Fire Performance of Concrete and Shotcrete Tunnel Liners

Abstract

Tunnel liners can suffer significant structural damage when exposed to long duration fires. The resulting damage to the tunnel liner can produce casualties, major service disruptions, and financial loss. Structural fire performance studies have generally focused on buildings exposed to standard fires. Tunnel fires typically have high temperatures and heat release rates compared to building fires. In this paper, an analytical method is provided for assessing the structural fire performance of concrete or the shotcrete tunnel liners, by comparing the structural demand and the capacity of the liners in the time domain. The suggested analysis is a combination of a heat transfer analysis and a nonlinear structural analysis that involves such factors as type of fire, concrete mix design, temperature-induced material degradation, and ground–tunnel liner interaction. A case study is provided. Techniques to minimize fire damage are recommended, and practical methods are suggested for repairing the fire-damaged concrete.