（1 西安科技大学建筑与土木工程学院， 西安 710054; 2 西安建筑科技大学土木工程学院， 西安 710055)

［摘要］为了更好地研究大气环境中的混凝土结构在冻融作用下的耐久性能，采用气冻气融的试验方法，对足尺（150mm×300mm×2 700mm）钢筋混凝土梁在不同冻融循环次数作用后的抗弯承载力进行了研究，分析了冻融对钢筋混凝土梁在静荷载作用下的裂缝发展规律、开裂荷载、极限荷载、跨中挠度以及混凝土截面应变的影响。研究结果表明：经过冻融循环作用后的钢筋混凝土梁在静荷载作用下，其裂缝发展规律与未冻融梁基本一致；随着冻融循环次数的增加，开裂荷载、极限荷载以及跨中挠度逐渐降低，冻融循环150次时，开裂荷载下降为未冻融时的60%，极限荷载下降为未冻融时的86-7%，跨中挠度下降为未冻融时的79%；混凝土截面应变符合平截面假定，且随着冻融循环次数增加，混凝土受压区高度有所增加。

［关键词］气冻气融； 开裂荷载； 极限荷载； 跨中挠度； 截面应变

中图分类号：TU375-1文献标识码：A文章编号：1002-848X(2018)22-0062-05

Experimental research on flexural bearing capacity of RC beam under air-freezing and air-thawing actions

Guan Xiao1, Niu Ditao2, Li Qiang1, Xiao Qianhui1

(1 School of Architecture and Civil Engineering, Xi′an University of Science and Technology, Xi′an 710054, China;2 School of Civil Engineering, Xi′an University of Architecture and Technology, Xi′an 710055, China)

Abstract:In order to better study the durability of concrete structures in the atmosphere under freezing and thawing, the test method of air-freezing and air-thawing was used to study flexural bearing capacities of the full-scale (150mm×300mm×2 700mm) reinforced concrete beams in different freeze-thaw cycles. The effects of freezing and thawing on the crack development law, cracking load, ultimate load, mid-span deflection and concrete cross-section strain of reinforced concrete beams under static load were analyzed. The study results show that the crack development law of reinforced concrete beams subjected to freeze-thaw cycles is basically the same as that of beams without freeze-thaw cycles. With the increase of freeze-thaw cycles, the cracking load, ultimate load and mid-span deflection  gradually reduce. When the freeze-thaw cycle  time is 150, the cracking load decreases to 60% at the time of non-freeze-thaw cycle, and the ultimate load decreases to 86-7% at the time of non-freeze-thaw cycle, and the mid-span deflection decreases to 79% at the time of non-freeze-thaw cycle. The concrete cross-section strain conforms to the flat section assumption, and as the number of freeze-thaw cycles increases, the concrete compression zone height increases.

Keywords:air-freezing and air-thawing; crack load; ultimate load; mid-span deflection; cross-section strain

*国家自然科学基金(51278403)，教育部长江学者和创新团队发展计划(IRT13089)。

作者简介：关虓，博士，讲师，Email: 86484869@qq.com。