受火后冷拔低碳钢丝预应力混凝土空心板受弯性能试验研究

摘要

To learn the mechanical performance of prestressed concrete hollow-core slabs with cold-drawn lowcarbon wire after exposed to fire,7 specimens were experimentally studied.In which including 3 control slabs and 4 slabs exposed to fire for 20 min,40 min,60 min and 80 min,respectively.The test results showed that the failure of control slabs and exposed slabs were all a bending failure mode.During the exposed procedure,the mid-span displacement of slabs increased with the exposed time,the mid-span displacement of the slabs exposed to fire for 20 min and 40 min could fully restored after cooling by air while the slabs exposed to fire for 60 min and 80 min decreased to nearly 15mm.When the exposed time extended,the crack load,ultimate load and initial bending stiffness of exposed slabs decreased with the exposed time increased,approximately with an linear relationship.The strain distributions along the height of the fire-damaged slabs at middle-span are nearly linear during the whole loading process,that is,a plan section remained almost plan.At the same load level,the tensile strain of bottom surface and the compressive strain of top surface of exposed slabs were all larger than the control slabs.%为比较不同受火时间后的力学性能,进行了7块冷拔低碳钢丝预应力混凝土空心板的对比试验研究,其中3块未受火对比试件,4块底面分别受火20 min、40 min、60 min和80 min试件.研究结果表明,对比试件和受火试件均发生弯曲破坏.升温过程中预制空心板跨中挠度随受火时间显著增加,熄火自然冷却后受火20 min和40 min的试件跨中挠度可恢复；而受火试件60 min和80 min的试件跨中残余挠度接近15 mm.随着受火时间延长,受火后预制空心板开裂荷载、极限荷载和初始弯曲刚度均明显降低,降低幅度基本与受火时间呈线性关系.受火后预制空心板跨中截面变形基本符合平截面假定,相同荷载作用下受火后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.