足尺钢框架结构中楼板受火试验研究

Fire test on floor of full-scale steel-framed structure

采用自制火灾试验炉对足尺钢框架结构中楼板的火灾行为进行试验研究。简要介绍了试验炉的设计、温度及变形测量方案,描述了试验现象以及楼板、钢梁和节点的破坏特征,分析了楼板、钢梁的截面温度分布规律和变形规律,并与相关试验结果进行了对比。结果表明:炉内温度基本均匀,停火时平均炉温约为780℃;升温时沿板厚具有较大的升温梯度,降温时存在降温滞后;升温阶段前期受火钢梁截面存在较大的升温梯度,后期截面温度基本一致;受火板格板顶裂缝模式主要取决于其边界条件,非受火板格裂缝特征取决于受火板格的位置及数量;由于受火组合梁产生反拱效应,受火板格中心位移存在一平缓阶段;因相邻结构约束较强,钢梁具有较好的抗火性能;与高强度螺栓连接节点相比,混合连接节点可有效防止钢梁出现局部屈曲。

A furnace was designed to study the fire behavior of the floor in a full-scale steel-framed structure. This paper presents the design of the furnace, the measurement method of temperature and deflection. The experimental phenomena as well as the failure characteristic of floor, steel beams and the connections were briefly discussed. The temperature distribution of the structural elements was analyzed in detail, together with their displacements. The test results were also compared with other testing results. The results indicate that the furnace temperature is basically even, the average furnace temperature at the shut-off time is about 780 ~C. For the concrete slab, there is larger temperature gradient during the heating stage and temperature lag phenomenon for the cooling phase. For the steel beam, there is large temperature gradient between the top and bottom flanges at the early stage, and the temperature is consistent later. It is observed that the top crack pattern of the heated panel is dependent on its boundary condition, and that of the unheated panel is dependent on the number and position of the heated panels. Due to the arc action of the heated composite beams, the mid-span deflection of each heated panel has a plateau. Owing to the constraint provided by other structural elements, the steel beam has better fire-resistant performance. Unlike the high-strength joint, the mixed joint orevents the steel beam from local buckling.