A comprehensive novel approach for fire analysis of tunnels structural design

Abstract

The main purpose of this paper is to present a comprehensive novel methodology for fire analysis of infrastructures, viz. tunnels, via studying the effects of a major fire event on a case study tunnel, Louis Hippolyte Lafontaine Tunnel (TLHL). A weak thermo-mechanical coupling analysis is performed via a staggered scheme to evaluate the structural integrity of the precast tunnel caissons when subjected to fire. The effect of explosive spalling on the tunnel’s structural integrity was evaluated based on saturated steam pressure (SSP) with a cut-off peak. In-situ tests were conducted to assess the spalling of concrete in the TLHL and calibrate the spalling parameters in the numerical models. Both in-situ tests and numerical models predicted that spalling occurs approximately within two minutes in the fire event, which leads to a reduction in tunnel cross-section and structural capacity and impacts the long-term durability of the tunnel. In this study, based on the analysis results, passive fire protections were suggested to prevent the loss in structural integrity. Furthermore, the numerical simulations considering ground-structure interaction were carried out to firstly predict the response of ground and tunnel caissons, secondly, confirm the adequacy of the structural design of the tunnel, and finally, to ascertain the performance of fire protection when the tunnel is subjected to fire.