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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。
In order to compare the similarities and differences of the residual bearing capacity, mid-span deflection and failure modes of prestressed concrete hollow slab after different fire time, seven prestressed concrete hollow slab specimens were made, of which three were not fire-tested and four The specimens were subjected to fire for 15 min, 30 min, 45 min and 60 min, respectively, and their contrastive studies on mechanical properties after fire were carried out. The results show that both the bending deformation and the bending deformation of the specimens are affected by bending. The mid-span deflection of prestressed concrete hollow slabs increases with the increase of exposure time, and most of the mid-span deflection recovers after flameout. The residual deflection is close to 20 mm; when the fire time is more than 15min, the cracking load and the failure load of the prestressed concrete hollow slab after fire are reduced; when the fire time reaches 60min, the cracking load and the failure load all drop sharply; The initial flexural rigidity of the tested specimens was significantly lower than that of the comparative specimens, and the magnitude of the decrease was basically linear with the duration of the fire. The tensile strain and the compressive edge strain of the specimens subjected to the same load were significantly greater than those of the comparative specimens The equivalent section method is used to calculate the bearing capacity of prestressed concrete hollow slab after fire, basically meeting the requirements of engineering accuracy.