The fire beam element method is a tool for structural fire analyses that simplifies a structure into a skeletal frame consisting of only beam and column elements. It considers a shifting neutral axis of each beam element, which is updated throughout an analysis. This method was implemented in the OpenSees software environment by adding two subclasses: one for the fire beam element added to the element class, and one for the member section, in which the neutral axis is iteratively adjusted for non-uniform temperature profiles. To validate the implemented model, three benchmark case studies were sourced from literature: (1) a heated cantilever beam with an analytical solution, (2) a steel beam in a furnace with high axial and bending forces and (3) a two-dimensional steel frame in a fire with complex behaviour such as non-linear heating, restraint and buckling. For (1) the fire beam element predicts deformations identical to an analytical solution. For (2) the fire beam element method simulates deformations with good accuracy across the entire time domain relative to experimental data, and simulations in the literature using Vulcan, although with experimental deflections typically being underestimated. For (3) fire beam element predictions are compared to experimental data and models developed in CEFICOSS, ABAQUS, SAFIR and LS-DYNA. Trends are typically accurately captured, with percentage differences varying. Runaway failure is predicted with 2 min of experimental data. A sensitivity analysis of the fire beam element model on mesh size of elements and fibres showed the runtime to be more sensitive to the number of elements than the number of fibres per element.

中文翻译：

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在 OpenSees 中实现火梁单元法，以分析火灾中的结构

火梁单元法是一种用于结构火灾分析的工具，可将结构简化为仅由梁和柱单元组成的骨架框架。它考虑了每个梁元素的移动中性轴，该中性轴在整个分析过程中都会更新。该方法是在 OpenSees 软件环境中通过添加两个子类实现的：一个用于添加到元素类中的火梁元素，另一个用于成员部分，其中中性轴针对非均匀温度分布进行迭代调整。为了验证实施的模型，三个基准案例研究来自文献：（1）具有解析解的加热悬臂梁，（2）具有高轴向力和弯曲力的炉中的钢梁和（3）二维火灾中的钢框架具有复杂的行为，例如非线性加热，克制和屈曲。对于 (1)，火梁单元预测变形与解析解相同。对于 (2)，火梁单元法在整个时域内相对于实验数据和使用 Vulcan 的文献中的模拟以良好的精度模拟变形，尽管实验偏转通常被低估。对于 (3) 火梁元素预测与在 CEFICOS、ABAQUS、SAFIR 和 LS-DYNA 中开发的实验数据和模型进行比较。趋势通常会被准确捕获，但百分比差异会有所不同。用 2 分钟的实验数据预测失控故障。火梁元素模型对元素和纤维的网格尺寸的敏感性分析表明，运行时间对元素数量比对每个元素的纤维数量更敏感。对于 (1)，火梁单元预测变形与解析解相同。对于 (2)，火梁单元法在整个时域内相对于实验数据和使用 Vulcan 的文献中的模拟以良好的精度模拟变形，尽管实验偏转通常被低估。对于 (3) 火梁元素预测与在 CEFICOS、ABAQUS、SAFIR 和 LS-DYNA 中开发的实验数据和模型进行比较。趋势通常会被准确捕获，但百分比差异会有所不同。用 2 分钟的实验数据预测失控故障。火梁元素模型对元素和纤维的网格尺寸的敏感性分析表明，运行时间对元素数量比对每个元素的纤维数量更敏感。对于 (1)，火梁单元预测变形与解析解相同。对于 (2)，火梁单元法在整个时域内相对于实验数据和使用 Vulcan 的文献中的模拟以良好的精度模拟变形，尽管实验偏转通常被低估。对于 (3) 火梁元素预测与在 CEFICOS、ABAQUS、SAFIR 和 LS-DYNA 中开发的实验数据和模型进行比较。趋势通常会被准确捕获，但百分比差异会有所不同。用 2 分钟的实验数据预测失控故障。火梁单元模型对单元和纤维的网格尺寸的敏感性分析表明，运行时间对单元数量比每个单元的纤维数量更敏感。