预制混凝土简支叠合板耐火性能试验研究

Experimental study on fire resistance performance of simply supported precast concrete composite slabs

进行了2块预应力和2块非预应力简支叠合板受火试验研究,分析了钢筋类别、板底是否涂抹水泥砂浆粉刷层对简支叠合板耐火极限的影响。观测了试件表面出现的渗水、粉刷层剥落和混凝土爆裂及外观颜色变化等宏观现象,研究了高温下截面温度场分布、试件弯曲变形的变化规律。试验结果表明:相同火灾条件下,预应力试件比非预应力试件更容易发生混凝土爆裂;所有试件均为跨中区域横向受拉裂缝引起的弯曲破坏,破坏时各试件的跨中挠度较大、延性较好;预应力筋会产生高温徐变和松弛,对构件高温受力性能更为不利,常温下等强配筋的预应力试件比非预应力试件耐火极限小;板底受力筋的温度是影响叠合板耐火极限的主要因素,板底粉刷层能延缓板底受力筋的升温,提高试件的耐火极限。

The fire resistance performance of two prestressed and two non-prestressed simply supported precast concrete composite slabs were tested. The influences of rebar type and mortar cover on bottom slab on fire endurance of the simply supported precast concrete composite slabs were analyzed. The macroscopical phenomena of the specimens were observed including water penetration,spalling of mortar cover,concrete burst and exterior color change. The distribution of temperature field along the depth of slabs and the chang law of flexural deformation under high temperature were investigated. Test results indicate that under the same fire condition,the prestressed specimens are more likely to have concrete burst than the non-prestressed ones. All specimens were flexural failure mode caused by transverse tension cracks in the middle regions,and have large mid-span deflection and good ductility at failure. The prestressed specimens have low fire endurance compared with the non-prestressed specimens with equal reinforcement at room temperature,because the prestressed tendons would produce high-temperature creep and relaxation and lead to worse mechanical performance under high temperature. The temperature of reinforced tendon at bottom slab is the main influence on fire endurance of the composite slabs,and the protective layer of cement mortar could delay the heating of internal tendons and improve fire resistance of the specimens.