This paper describes the development and illustrates the use of an approach to model the mechanical performance of a concrete bridge and its structural components exposed to fire and subject to spalling. The work is motivated by some recent fire incidents that involved concrete bridges, the poor state of an increasing number of bridges throughout the United States (which makes them more vulnerable to fire damage), and the lack of design codes and standards that adequately protect bridges against fire. An important objective of the work is to develop a method to predict spalling that captures the principal physical and chemical phenomena but is simple enough so that it can be implemented in a 3‐D structural simulation. The first step in the approach involves using a hydrothermal model to determine if and at what temperature spalling occurs for a specified concrete mix (defined by its composition, type of aggregate, water‐cement ratio, porosity, permeability, etc), free moisture content, and heating rate. The second step uses the resulting “critical spalling temperature” in a coupled thermal and mechanical analysis to determine how spalling affects the performance of the concrete member. The approach is illustrated for two standard fire resistance tests conducted on posttensioned concrete slab systems reported in the literature. The paper concludes with a list of recommendations for additional work to improve the predictive capability of the heat and mass transfer and structural models and to address several challenges with the implementation of the spalling criteria in the structural model.

中文翻译：

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混凝土构件火灾和结构相互作用的模拟方法的开发与应用

本文描述了这一发展过程，并说明了使用一种方法来对混凝土桥梁及其暴露于火中并易于剥落的结构部件的机械性能进行建模的方法。这项工作的动机是最近发生的一些火灾事件，涉及混凝土桥梁，全美国桥梁数量不断增加的恶劣状态（这使得它们更容易遭受火灾破坏）以及缺乏足够保护桥梁的设计规范和标准。防火。这项工作的一个重要目标是开发一种预测剥落的方法，该方法可以捕获主要的物理和化学现象，但又非常简单，因此可以在3D结构仿真中实现。该方法的第一步涉及使用水热模型来确定特定混凝土混合物（由其成分，骨料类型，水灰比，孔隙率，渗透性等定义）是否发生散裂以及在何种温度下发生散裂。 ，以及加热速率。第二步在热力和机械分析的耦合中使用结果“临界剥落温度”来确定剥落如何影响混凝土构件的性能。文献报道了在后张拉混凝土板系统上进行的两个标准耐火性测试，说明了该方法。