火灾下玻璃裂纹扩展演化规律及脱落机理研究

The glass fallout plays an important role in the spread process of building fires. The glass fallout makes the window a vent, which accelerates the fire growth and forms a new channel for fire to spread to adjacent regions. This project will use a combination of experiments, numerical simulation and theoretical analysis, and intends to select the float glass and low-e glass, which are the widely used in the construction and have poor fire resistance, as the research object. The behavior of crack propagation of glass under different heat flows and different frame constraints will be studied by using the apparatus for studying glass breakage and fallout under thermal loading, the three-dimensional fire spread test platform in high-rise building, some measurement instruments including high-speed camera, high-precision electronic balance, heat flow meter, and thermocouples, and finite element simulation based on the phase field model. As a result, the dynamic evolution law and mechanism of glass crack propagation under the coupling effect of heat flow and frame constraint will be revealed. The force status of cracked glass islands and critical condition of the cracked glass islands fallout will be studied to reveal the mechanism of the glass fallout under fire conditions and to build the criterion and prediction model of the glass fallout. To sum up, the implementation of this project will provide a theoretical basis and technical support for the fire-resistant design of glass.

玻璃的脱落在建筑火灾蔓延过程中扮演着重要的角色。玻璃脱落形成通风口，加速火灾发展，同时会形成新的火蔓延通道，向相邻区域蔓延。本项目拟采用实验、数值模拟和理论分析相结合的方法，以建筑上应用广泛且抗火性能较差的浮法玻璃和低辐射镀膜玻璃为研究对象，使用热载荷作用下玻璃破裂脱落实验台和高层建筑立体火蔓延实验台，利用高速摄像机、高精度电子天平、热流计、热电偶等测量设备，以及基于相场模型的有限元模拟技术，研究不同热流、不同边框约束形式等参数条件下玻璃裂纹的扩展行为，揭示边框约束形式和热流耦合作用下玻璃裂纹扩展的动态演化规律及内在作用机制，研究玻璃“孤岛”的受力状态以及发生脱落时的临界条件，揭示火灾下玻璃的脱落机理，建立火灾下玻璃脱落的临界判据和预测模型，为玻璃的抗火设计提供理论依据和技术支撑。

玻璃的抗火性能有限，火灾下玻璃窗或玻璃幕墙结构往往是建筑中最薄弱的环节。在外界环境与火灾的共同作用下，玻璃脱落一方面将加速以通风控制主导的室内火灾发展；另一方面将加速火灾向隔壁区域蔓延。因此，玻璃的破裂、脱落行为在形成高层建筑内-外交互立体火蔓延的过程中起到了重要的作用。本项目采用实验和数值模拟相结合的方法，以建筑上应用广泛且抗火性能较差的浮法玻璃为研究对象，研究了火灾下不同安装形式对点支承浮法玻璃破裂行为的影响，揭示了玻璃首次破裂时间、裂纹扩展以及脱落的规律，结合数值优化建模，给出了抗火性能较优的安装形式；采用相场模型，研究了不同边框约束和不同热流条件下玻璃的裂纹成核及扩展行为，揭示了边框约束和热流耦合作用下玻璃裂纹扩展的动态演化规律及内在作用机制。此外，发展了平滑有限元法，通过引入能量平衡恢复法，提出了一种精度较高模拟脆性材料(例如玻璃)动态裂纹扩展的数值方法。本项目的研究结果可为玻璃窗和玻璃幕墙的抗火设计提供理论依据和技术支撑。