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Concurrent fire dynamics models and thermomechanical analysis of steel and concrete structures.

机译：钢和混凝土结构的同时火灾动力学模型和热力学分析。

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摘要

The objective of this study is to formulate a general 3D material-structural analysis framework for the thermomechanical behavior of steel-concrete structures in a fire environment. The proposed analysis framework consists of three modeling parts: fire dynamics simulation, heat transfer analysis, and a thermomechanical stress analysis of the structure. The first modeling part consists of applying the NIST (National Institute of Standards and Technology) fire dynamics simulator (FDS) where coupled Computational Fluid Dynamics (CFD) with thermodynamics are combined to model the fire progression within the steel-concrete structure. The goal is to generate the spatial-temporal (ST) solution variables (temperature, heat flux) on the surfaces of the structure. The FDS-ST solutions are generated in a discrete numerical form. Continuous FDS-ST approximations are then developed to represent the temperature or heat-flux at any given time or point within the structure. An extensive numerical study is carried out to examine the best ST approximation functions that strike a balance between accuracy and simplicity. The second modeling part consists of a finite-element (FE) transient heat analysis of the structure using the continuous FDS-ST surface variables as prescribed thermal boundary conditions. The third modeling part is a thermomechanical FE structural analysis using both nonlinear material and geometry. The temperature history from the second modeling part is used at all nodal points. The ABAQUS FE code is used with newly developed external user subroutines for the second and third simulation parts. The main objective is to describe the nonlinear temperature-dependency of the specific heat of concrete materials, especially high-strength concretes, that drastically affects their transient thermal solution. New algorithms are also developed to apply the continuous FDS-ST surface nodal boundary conditions in the transient heat FE analysis. The proposed modeling framework is applied to predict the temperature and deflection of the well-documented Cardington fire tests and to predict the time-to-collapse of the recent Oakland bridge fire caused by a fuel-truck accident.
机译：这项研究的目的是为火灾环境下的钢-混凝土结构的热机械行为建立一个通用的3D材料-结构分析框架。所提出的分析框架包括三个建模部分：火灾动力学模拟，传热分析和结构的热机械应力分析。第一个建模部分包括应用NIST（美国国家标准技术研究院）火灾动力学仿真器（FDS），其中将计算流体动力学（CFD）与热力学结合起来，以对钢混凝土结构内的火灾进行建模。目的是在结构表面上生成时空（ST）解变量（温度，热通量）。 FDS-ST解决方案以离散的数字形式生成。然后开发出连续的FDS-ST近似值，以表示结构内任何给定时间或点的温度或热通量。进行了广泛的数值研究，以研究在精度和简单性之间取得平衡的最佳ST逼近函数。第二个建模部分包括使用连续FDS-ST表面变量作为规定的热边界条件对结构进行有限元（FE）瞬态热分析。第三建模部分是同时使用非线性材料和几何形状的热机械有限元结构分析。第二个建模部分的温度历史记录用于所有节点。 ABAQUS FE代码与新开发的外部用户子例程一起用于第二和第三模拟部分。主要目的是描述混凝土材料（特别是高强度混凝土）的比热的非线性温度依赖性，该温度极大地影响其瞬态热解。还开发了新算法，将连续FDS-ST表面节点边界条件应用于瞬态热FE分析中。拟议的建模框架可用于预测有据可查的Cardington火灾测试的温度和挠度，并预测最近因燃油卡车事故引起的奥克兰桥梁火灾的崩溃时间。

著录项

  • 作者

    Choi, Joonho.;

  • 作者单位

    Georgia Institute of Technology.;

  • 授予单位 Georgia Institute of Technology.;
  • 学科 Engineering Civil.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 220 p.
  • 总页数 220
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 建筑科学;
  • 关键词

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