Abstract This paper highlights the nature of the problem related to tunnel liners exposed to fire, and presents a possible approach for assessing the static behaviour of concrete structures under this extreme loading condition. The paper starts with some comments regarding material parameters for concrete subjected to high temperatures proposed by the European Standards. Subsequently, the main aspects to be considered in a structural fire analysis for a tunnel are highlighted by means of a simple calculation scheme. Based on this scheme, an advanced calculation method for assessing the structural behaviour of concrete tunnel linings during a fire event is described and validated. The classic approach commonly used for structural static analyses based on thin elements (beam or shell) is not particularly suitable for determining section forces in concrete structures exposed to temperature changes. This limited adequacy emerges especially in the case of fire. In such cases, the impact of a temperature increase on the structural behaviour could be significantly overestimated. The proposed approach for tunnel fire verification, by properly considering the concrete cracking, provides more realistic results, avoiding unnecessary over-dimensioning of steel reinforcements in new structures, or the protection of existing structures by, for example, additional insulating layers.

中文翻译：

---

隧道火灾验证的实用方法

摘要 本文强调了与暴露在火灾中的隧道衬砌相关的问题的性质，并提出了一种评估这种极端载荷条件下混凝土结构静态性能的可能方法。本文首先对欧洲标准提出的高温混凝土材料参数进行了一些评论。随后，通过简单的计算方案突出显示了隧道结构火灾分析中要考虑的主要方面。基于该方案，描述并验证了一种用于评估火灾事件期间混凝土隧道衬砌结构性能的高级计算方法。通常用于基于薄单元（梁或壳）的结构静力分析的经典方法并不特别适合确定暴露于温度变化的混凝土结构中的截面力。这种有限的充足性尤其在发生火灾的情况下出现。在这种情况下，温度升高对结构行为的影响可能会被大大高估。通过适当考虑混凝土开裂，建议的隧道火灾验证方法提供了更真实的结果，避免了新结构中不必要的钢筋尺寸过大，或通过例如额外的绝缘层来保护现有结构。温度升高对结构行为的影响可能被严重高估。通过适当考虑混凝土开裂，建议的隧道火灾验证方法提供了更真实的结果，避免了新结构中不必要的钢筋尺寸过大，或通过例如额外的绝缘层来保护现有结构。温度升高对结构行为的影响可能被严重高估。通过适当考虑混凝土开裂，建议的隧道火灾验证方法提供了更真实的结果，避免了新结构中不必要的钢筋尺寸过大，或通过例如额外的绝缘层来保护现有结构。