预应力混凝土空心板受火后力学性能试验研究

为比较不同受火时间后预应力混凝土空心板剩余承载力、跨中挠度和破坏形态的异同，制作了7块预应力混凝土空心板试件，其中3块为未受火对比试件，4块为底面分别受火15 min，30 min，45 min和60 min试件，对其开展受火后力学性能的对比研究。研究结果表明：对比试件和受火试件均发生弯曲破坏；升温过程中预应力混凝土空心板跨中挠度随受火时间增加而显著增加，熄火自然冷却后跨中挠度大部分可恢复，跨中残余挠度接近20 mm；受火时间大于15min时，受火后预应力混凝土空心板开裂荷载和破坏荷载均有所降低；当受火时间达到60 min时，开裂荷载和破坏荷载均急剧下降；受火试件初始弯曲刚度较对比试件明显降低，降低幅度基本与受火时间呈线性关系；相同荷载作用下受火试件受拉边缘拉应变和受压边缘压应变均明显大于对比试件；采用等效截面法计算受火后预应力混凝土空心板的承载力基本满足工程精度要求。

Experimental research on mechanical behavior of PC hollow-core slab exposed to fire

To learn the fire performance such as residual bearing capacity,mid-span displacement and failure mode of prestressed concrete hollow-core slabs exposed to fire,7 specimens were experimentally studied,including 3 control slabs and 4 slabs exposed to fire for 15 min,30 min,45 min and 60min,respectively.The test results show that the failure of control slabs and exposed slabs are all a bending failure mode.During the firing procedure,the mid-span displacement of slabs increases with the exposing time,and after cooling by air the mid-span displacement decreases to nearly 20 mm.When the exposing time is longer than 15 min,the cracking load and ultimate load are all decreased slightly.When the exposing time reaches 60 min,the cracking load and ultimate load are all decreased sharply.The initial bending stiffness of exposed slabs decreases with the exposing time increased.At the same load level,the tensile strain of the bottom surface and the compressive strain of the top surface of exposed slabs are all larger than those of the control slabs.The calculation results can be obtained easily in practice based on the equivalent cross-section and taking the fire damage of concrete and reinforcement into consideration.