Abstract This work aims to provide a comprehensive procedure for the assessment of structural safety of tunnel linings exposed to fire. To this purpose, numerical simulations that model the three fundamental features influencing tunnel fire safety design, namely fire dynamics, thermal behavior and structural response, are performed. Fire development within tunnel is simulated by applying advanced Computational Fluid Dynamics (CFD) techniques under a Fire Safety Engineering (FSE) approach. CFD fire simulation is carried out first, and then the results are transferred into a thermo-mechanical Finite Element (FE) model. A “sequentially coupled thermo-mechanical analysis” is then performed by linking a heat-transfer analysis that provides the temperature distribution within the lining with a refined non-linear mechanical simulation. A proper non-linear constitutive model for concrete subjected to high temperature, able to account the main features governing concrete behavior (i.e. cracking and crushing), is applied to the purpose. Comparisons in terms of structural results obtained by applying this coupled procedure and those obtained through a thermo-mechanical analysis adopting a standard time-dependent fire curve are provided. The importance of considering a refined simulation of the fire scenario is proved: from a structural point of view, significant differences concerning stress distribution and cracking development in the lining are indeed observed. Therefore, the use of a realistic model to describe fire development appears crucial to understand the behavior of unreinforced concrete linings subjected to fire and to control their possible weaknesses, such as the appearance of cracks.

中文翻译：

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基于 CFD 火灾的混凝土隧道衬砌结构安全评估模拟方法——有限元热机械分析：案例研究

摘要 这项工作旨在为评估暴露在火灾中的隧道衬砌的结构安全性提供一个综合程序。为此，对影响隧道消防安全设计的三个基本特征，即火灾动力学、热行为和结构响应进行了数值模拟。通过在消防安全工程 (FSE) 方法下应用先进的计算流体动力学 (CFD) 技术来模拟隧道内的火灾发展。首先进行 CFD 火灾模拟，然后将结果转换为热机械有限元 (FE) 模型。然后通过将提供衬里内温度分布的传热分析与精细的非线性机械模拟相联系来执行“顺序耦合热机械分析”。一个适用于高温混凝土的非线性本构模型，能够考虑控制混凝土行为（即开裂和压碎）的主要特征，用于此目的。提供了通过应用此耦合程序获得的结构结果与通过采用标准时间相关燃烧曲线的热机械分析获得的结构结果的比较。考虑对火灾场景进行精细模拟的重要性得到了证明：从结构的角度来看，确实观察到衬砌中应力分布和开裂发展的显着差异。因此，使用现实模型来描述火灾发展对于了解无钢筋混凝土衬里遭受火灾的行为并控制其可能的弱点似乎至关重要，