超大保护层钢筋混凝土梁短期裂缝宽度试验研究  

Experimental research on short-term crack width for reinforced concrete beams with super concrete cover

作　　者：李平先[1] 张炎龙 王卫国[2] LI Pingxian;ZHANG Yanlong;WANG Weiguo(School of Water Conservancy Engineering,Zhengzhou University,Zhengzhou 450001,China;Northwest Engineering Corporation Limited,Power China,Xi’an 710065,China)

机构地区：[1]郑州大学水利科学与工程学院,河南郑州450001 [2]中国电建集团西北勘测设计研究院有限公司,陕西西安710065

出　　处：《建筑结构学报》2022年第6期11-20,共10页Journal of Building Structures

基　　金：清华大学水沙科学与水利水电工程国家重点实验室开放基金(sklhse-2018-C-04)。

摘　　要：为研究超大保护层水工钢筋混凝土梁的裂缝特征以及评估其对DL/T 5057—2009《水工混凝土结构设计规范》裂缝宽度计算公式的适用性,进行了10根截面宽度为200~300 mm、高度为400~1 000 mm、保护层厚度为25~150 mm配置HRB400钢筋混凝土简支梁的受弯性能试验,得到梁的开裂荷载、裂缝间距的大小与分布、裂缝宽度等,分析了混凝土保护层厚度对梁的裂缝间距和裂缝宽度的影响,结合短期裂缝试验结果,采用DL/T 5057—2009《水工混凝土结构设计规范》的裂缝计算公式进行了对比计算。结果表明:在正常使用状态下,当混凝土保护层厚度小于60 mm时,裂缝平均间距随保护层厚度的增大而增加;当混凝土保护层厚度超过60 mm时,保护层厚度对裂缝平均间距影响不大;平均裂缝间距、平均裂缝宽度和短期最大裂缝宽度试验值与按DL/T 5057—2009计算的结果相比总体上偏小。根据试验结果并参考相关规范,给出平均裂缝间距计算式,并根据黏结滑移理论得到了适用于超大保护层厚度的钢筋混凝土梁短期最大裂缝宽度计算式,经与裂缝试验资料对比计算,其短期最大裂缝宽度与试验结果吻合较好。Ten simply supported rectangular reinforced concrete beams, with width 200 mm to 300 mm, total depth of 400 mm to 1 000 mm, cover thickness from 20 mm to 150 mm, reinforced with Grade HRB400 bars were tested to evaluate the applicability of crack formulas specified in the design specification for hydraulic concrete structures(DL/T 5057—2009) and to study the cracking characteristics of reinforced concrete beams with very thick cover thickness. The cracking load, crack spacing and distribution, and crack width were obtained. The effects of the cover thickness on both crack spacing and crack width were investigated. Based on short-term crack test results, the formulas for cracking in design specification for hydraulic concrete structures DL/T 5057—2009 were compared. The test results indicate that, under normal working conditions, the average crack spacing increases with the increase of concrete cover thickness when the cover thickness doesn’t exceed 60 mm, while when the concrete cover thickness exceeds 60 mm, the cover thickness has little influence on the average crack spacing. The results of average crack spacing, average crack width, and short-term maximum crack width are generally lower than that predicted by the formulas of code DL/T 5057—2009. The calculation formula of average crack spacing, which contains the cover thickness, diameter of bars and effective reinforcement ratio, was proposed based on relevant specifications and the test results. In addition, the modified calculation formulas of crack width were proposed based on bond-slip theory and the test results, which can estimate the short-term maximum crack width of reinforced concrete beams with very thick concrete cover. The proposed short-term maximum crack width formula agrees with the experimental results.

关 键 词：超大保护层 HRB400钢筋 钢筋混凝土梁 受弯性能试验 黏结滑移理论 短期最大裂缝宽度 

分 类 号：TU375[建筑科学—结构工程] TU317.1