Advanced Finite Element Fire Calculation in Tunnel Design

The finite element method provides a powerful tool for nonlinear numerical analysis of engineering structures. Although significant progress in the constitutive modeling of concrete and shotcrete behaviour has been made, very few of these models deal with the effect of high temperature on concrete or shotcrete. This research work developed a relatively comprehensive and sophisticated model, the Willam-Wranke five-parameter model, to describe concrete as well as shotcrete deformational and strength behavior under normal and high temperatures. A highly sophisticated Isoparametric Sandwich Shell Element (ISSQ) model that can have many layers is very useful for simulating the behavior of the shell structures, because it has the ability to separately specify a different material as well as different properties for each layer. The model also has the ability to specify a different temperature for each layer as well as constant or linear temperature distribution through the element thickness, which will be helpful for fires in tunnel structures. The model was applied to a tunnel for the case of fire loading. This helps answer many questions about the safety of tunnels in case of fire. The results show that taking fire loading into consideration is of great importance when designing concrete tunnel lining, because very high temperatures can cause total failure in some parts of the tunnel lining.