火灾下预应力板混凝土爆裂规律试验研究  

Experimental study on spalling of concrete of prestressed slabs in fire

作　　者：郑文忠[1] 许名鑫[1] 石东升[1] 胡琼[1] 

机构地区：[1]哈尔滨工业大学,黑龙江哈尔滨150090

出　　处：《土木工程学报》2006年第10期48-53,共6页China Civil Engineering Journal

基　　金：黑龙江省杰出青年科学基金(2001-8)

摘　　要：在火灾下预应力板迎火面的混凝土若发生爆裂,受力钢筋将裸露于火中,板将因钢筋被烧断而很快丧失承载力。完成了14块无黏结预应力混凝土简支单向板、1块先张预应力混凝土简支板和9块两跨预应力混凝土连续单向板的抗火试验,描述了8块简支板及3块连续板混凝土爆裂、受拉钢筋被烧断及裂缝分布与开展情况。得到了迎火面压应力水平越高或拉应力水平越低、常温下混凝土强度等级及含水率越高,混凝土越容易发生爆裂或爆裂越严重的初步结论。基于试验结果,首先提出了以常温下混凝土标准立方体抗压强度平均值为横坐标,以火灾下预压区板边缘混凝土正应力水平为纵坐标的混凝土爆裂上包线表达式和以常温下混凝土含水率为横坐标,以火灾下预压区板边缘混凝土正应力水平为纵坐标的混凝土爆裂上包线表达式;为便于设计应用,随后还提出了以常温下混凝土标准立方体抗压强度平均值为横坐标,以常温下预压区板边缘混凝土正应力水平为纵坐标的混凝土爆裂上包线表达式和以常温下混凝土含水率为横坐标,以常温下预压区板边缘混凝土正应力水平为纵坐标的混凝土爆裂上包线表达式。为初步判断火灾下混凝土爆裂的可能性提供了参考依据。If the concrete of a prestressed slab spalls in fire, the reinforcement will be exposed to flame, and the slab would soon lose its bearing capacity due to breaking of reinforcement caused by burning. Fire experiments are conducted on fourteen simply supported unbonded prestressed concrete slabs, one simply supported pretensioned prestressed concrete slab and nine two-span prestressed concrete continuous slabs. The spalling of concrete, breaking of tension reinforcements, distribution and development of cracks for 8 simple slabs and 3 continuous slabs are described. Preliminary conclusions are： concrete spalls more easily or more seriously when the compressive stress is higher or the tensile stress is lower in the surface exposed to fire, and when the strength of concrete and water content in concrete at normal temperature are higher. Based on the test results, two expressions of top envelope curve for concrete spalling are presented by taking the average standard concrete cubic strength at normal temperature as the x- axis and the normal stress level of concrete extreme fiber in pre-compression zone of slab in fire as the y-axis, and taking the water content in concrete at normal temperature as the x-axis and the normal stress level of concrete extreme fiber in pre-compression zone of slab in fire as the y-axis; to facilitate design and application, two expressions of top envelope curve of concrete spalling are presented by taking the average standard concrete cubic strength at normal temperature as the x-axis and normal stress level of concrete extreme fiber in pre-compression zone of slab at normal temperature as the y-axis, and taking the water content in concrete at normal temperature as the x-axis and normal stress level of concrete extreme fiber in pre-compression zone of slab at normal temperature as the y-axis.

关 键 词：火灾 预应力板 混凝土 含水率 爆裂 

分 类 号：TU378[建筑科学—结构工程] TU973.34