蔓延火灾下钢框架结构抗火性能试验研究

为研究蔓延火灾下钢框架结构建筑室内火灾温度场、钢构件温度分布和位移的发展规律，对1个足尺的两层钢框架结构进行蔓延火灾试验，测量试验区域内关键位置的空气温度、钢构件温度和位移。试验结果表明：试验中火源房间内的火灾过程呈现4个明显的发展阶段，受火70min时室内火灾达到全盛，测得火灾烟气层最高温度730℃；受火82min时火灾从火源房间蔓延至邻近房间，导致了邻近房间内各受火钢构件温度峰值出现在不同时刻，同时，各构件历经扩散热烟气加热、直接受火加热和冷却降温3个阶段，呈现反复升降温的受火过程；受火过程中，钢构件温度变化显著滞后于火场温度，受火钢柱先后升温产生向上的轴向变形。与传统室内火灾相比，蔓延火灾扩大了火场范围和钢结构受火范围，对结构安全和人员安全造成更大威胁，因此在进行结构抗火设计时应得到充分考虑。

Research on fire resistance test of a steel frame building under spreading fire

To investigate the structural response and the temperature distribution within the compartments and steel members of steel frame buildings under spreading fire, a spreading fire test was conducted on a full-scale two-storey steel frame. The test covers measurements of gas temperature at the scene of fire, cross-sectional temperature distribution of steel members and displacements of steel members at key parts. The test results show that four distinct stages are identified in the fire-source compartment where a fully developed fire in 70min is observed with the highest temperature of 730℃ of the smoke layer. The flames are observed to spread to the adjacent compartment in 82 min, which causes various temperature peaks of fire-exposed steel components in the adjacent compartment appeared at different moments. Moreover, the spreading fire also results in three-stage repeated heating and cooling process of steel members, i.e., diffused hot smoke, direct heating of the fire and cooling. During the fire process, the temperature variation of steel members lags behind that of the surrounding gas, and the fire-exposed columns are heated up successively to produce upward axial displacement. Therefore, full consideration of spreading fire is necessary for the design of structural fire resistance since it expands the fire igniting field and fire-exposed surfaces of the structure and poses a severer threat to structural safety and life security compared with the traditional compartment fire.