柱支承现浇混凝土空心楼盖抗火性能试验研究

Experimental study on fire resistance of column supported cast-in-suite concrete hollow floor

现浇混凝土空心楼盖具有自重轻、跨度大等优点,已广泛应用于实际工程中,而其抗火性能是影响建筑物抗火能力的一个重要因素。文章通过柱支承足尺现浇混凝土空心楼盖的火灾试验,分析了楼盖的破坏特征、温度场分布及挠曲变形,对楼盖的抗火性能进行研究。结果表明:柱对板角的约束作用导致板的4个角部出现了多条类弧状裂缝,裂缝与相邻两板边近似成45°,同时,梁柱节点区出现了明显的斜裂缝;混凝土的热惰性及空腔的阻热作用使混凝土空心楼盖沿截面高度存在较大的温度梯度,导致了温度应力的出现;试验过程中,混凝土空心楼盖未出现刚度突变的情况,数据采集至20 h时,跨中残余变形为17.7 mm,恢复比例达80.7%,表明空心楼盖受火灾作用后的变形恢复能力较强;相较于四边简支现浇混凝土空心楼盖,由于柱对空心楼盖的约束作用,其破坏特征更趋近于真实结构中的破坏现象,且变形恢复能力更强。

Cast-in-suite concrete hollow floor has been widely used in buihlings because of its advantage of light weight and large span. Its fire resistance is an important taetor affecting fire resistance of buildings. For investigating temperature field distribution and the destruetional forms of concrete hollow floor in the fire, east-in-suite column supported concrete hollow floor is researched in fire under load. Test slab＇ s destruction, temperature field distribution and deflection are analysed to research the fire resistance of hollow floor. The results show that a number of cracks which are similar to are are found on four board corners because of constraint of columns. The cracks are approximately 45 degrees to the edge of the two adjacent plates. The exterior concrete of the beam-column joint is pulled off, the steel bar is exposed, and the whole core area has an obvious oblique crack. Due to the thermal inertia of concrete and the thermal resistance of the cavity, there is obvious temperature gradient along the thickness direction of the concrete hollow floor. There is no abrupt change of stiffness in the concrete hollow floor.The recovery rate is 80.7% in the midspan, which indicates that the hollow floor has great capacity of deformation reeovery alter the high temperature. Compared with the simple east-in-place concrete hollow floor, the damage characteristics of the hollow floor are closer to the real damage, and the deformation recovering capacity is greater.