摘要
结合DIC技术对预埋螺栓式钢纤维混凝土试件展开直接拉伸试验,研究了钢纤维体积掺量、钢纤维长度和钢纤维类型对钢纤维混凝土开裂模式、抗拉强度、峰值应变以及裂后延性的耦合影响规律。研究结果表明:钢纤维混凝土在直接拉伸过程中的开裂声响、裂缝形态及裂缝数目等特性受钢纤维掺量影响显著;掺入钢纤维后混凝土的抗拉强度、峰值应变及裂后延性均有不同程度增加;相较于铣削型钢纤维浇筑时易出现重叠和成团现象,端钩型钢纤维更易浇筑均匀及密实,与混凝土基体间形成更加紧密的黏结,拉伸后期端部弯钩的变形抵抗力提升了桥联作用,端钩型钢纤维对抗拉强度和裂后延性的提升表现较优越。结合DIC结果进一步揭示了钢纤维混凝土直接拉伸作用下的细观破坏机理,钢纤维混凝土拉伸破坏可以分解为4个阶段:Ⅰ弹性阶段、Ⅱ细观裂缝稳定扩展阶段、Ⅲ裂缝失稳扩展阶段、Ⅳ纤维拔出阶段。根据试验结果建立了综合考虑混凝土基体特性、钢纤维体积掺量、钢纤维长度及钢纤维类型影响的钢纤维混凝土应力-应变模型,在此基础上,引入拉伸损伤因子综合考虑抗拉强度、峰值应变以及裂后延性对钢纤维混凝土损伤发展特性的影响。
The coupling effects of the content,length,and type of fiber on the cracking mode,tensile strength,peak strain,and post-cracking ductility were studied using direct tensile tests of steel fiber-reinforced concrete(SFRC)and DIC technology.The experimental results showed that the cracking sound,crack shape,and number of cracks in SFRC under direct tension were significantly affected by the content of steel fiber.The tensile strength,peak strain,and postcracking ductility all increased after adding steel fiber to the concrete.Compared with milled steel fibers,which tend to form agglomerates during pouring,hooked steel fibers are easier to pour uniformly and densely with the concrete matrix,and the resistance of the end hook greatly improves the bridging effect.Thus,the hooked steel fibers have a superior performance in improving the tensile strength and post-cracking ductility.The mesoscale failure mechanism of SFRC under direct tension was further revealed.The mesoscale failure of SFRC occurred in four stages.StageⅠwas the elastic stage;stageⅡinvolved mesoscale crack propagation;stageⅢwas mesoscale crack failure;and stageⅣincluded the pulling-out of the fibers.Consequently,a stress-strain model of SFRC was proposed that considered the coupling effects of the concrete matrix characteristics,fiber volume content,fiber length,and fiber type.Based on this model,a tensile damage factor was introduced to quantitatively investigate the effects of the tensile strength,peak strain,and post-cracking ductility on the damage development characteristics of SFRC.
作者
张冬梅
张鑫
ZHANG Dong-mei;ZHANG Xin(College of Civil Engineering,Tongji University,Shanghai 200092,China;Key Laboratory of Geotechnical and Underground Engineering of Minister of Education,Tongji University,Shanghai 200092,China)
出处
《中国公路学报》
EI
CAS
CSCD
北大核心
2023年第4期146-156,共11页
China Journal of Highway and Transport
基金
国家自然科学基金项目(51978517)
上海市教委重大项目(2019-01-07-00-07-456 E00051)
关键词
隧道工程
钢纤维混凝土
直接拉伸试验
应力-应变模型
细观损伤机理
tunnel engineering
steel fiber reinforced concrete
direct tensile test
stress-strain model
mesoscale damage mechanism
作者简介
张冬梅(1975-),女,山东菏泽人,教授,博士研究生导师,工学博士,E-mail:dmzhang@tongji.edu.cn。
