四边简支现浇混凝土空心楼盖火灾试验研究

Stady on test of fire resistance of simply supported on four sides of cast-in-place concrete hollow floor

现浇混凝土空心楼盖适用于大跨度、大空间的建筑物,且承载力大,已在工程中大量推广使用。但是现阶段对于现浇混凝土空心楼盖火灾行为的研究较少,其中对火灾中楼盖的温度场分布和破坏形式的研究显得尤为重要。文章对四边简支足尺现浇混凝土空心楼盖在使用荷载和火灾耦合作用下进行火灾试验,并对试验板的破坏特征形式、温度场分布和平面内外变形进行分析。结果表明:试验板温度场存在较大的温度梯度,肋梁底面混凝土与顶面混凝土最大温差可达550℃,空腔处板底混凝土与板顶混凝土最大温差约为660℃,导致温度应力产生,使板的上部受拉,出现垂直于板边的裂缝;空腔在火灾中能够减少热量传递降低楼板上表面和肋梁侧面温度;试验板跨中最大竖向位移为72.5 mm,平面内最大水平位移为10 mm;在整个试验过程中,试验板未出现被烧穿的现象,同时变形恢复比可达70%,具有很好的抗火性能。

The cast-in-situ concrete hollow floor with large span, heavy load, large space, flat plate beam technology, has been applied to a number of major projects. The present stage for the research on fire behavior of cast-in-situ concrete hollow floor is still less, and it is particularly important in the fire temperature field distribution and the form of destruction. In this paper, four edges simply support full-scale in-situ concrete hollow floor in fire under the coupling action of load and fire is presented, and test slab,s temperature field distribution, in-plane and out of plane deformation and destruction are analyzed. The results show that there is an obvious temperature gradient inside the test floor, the maximum temperature difference of the rib beam and cavity can reach 550 °C and 660 °C , causing the temperature stress, making the upper part of the plate to be pulled and appearing perpendicular cracks to the edge of the plate. Cavities can block the partial heat transfer in fire and reduce the temperature on the upper surface of the floor and the side of the rib beams. The maximum vertical displacement of the test plate is 72.5 mm, and the maximum horizontal displacement is 10 mm. Throughout the test, the floor has not been burned through and the deformation recovery ratio is up to 70% , showing better fire resistance ability.