| UHPC直剪性能试验与直剪承载力计算方法 |
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| 引用本文： | 冯峥,李传习,潘仁胜,周佳乐,柯璐,柯红军.UHPC直剪性能试验与直剪承载力计算方法[J].中国公路学报,2021,34(8):78-90. |
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| 作者姓名： | 冯峥 李传习 潘仁胜 周佳乐 柯璐 柯红军 |
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| 作者单位： | 1. 长沙理工大学 桥梁与建筑绿色建造与维护湖南省重点实验室, 湖南 长沙 410004;2. 长沙理工大学 桥梁工程安全控制教育部重点实验室, 湖南 长沙 410004;3. 广西大学 土木建筑工程学院, 广西 南宁 530004 |
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| 基金项目： | 国家自然科学基金项目（51778069，52078059，51808055）；桥梁工程领域省部级重点实验室开放基金项目（18KE04） |
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| 摘 要： | 针对超高性能混凝土（UHPC）直剪性能研究较为缺乏的现状，开展24个“Z”形UHPC整体浇筑试件和24个“Z”形UHPC平接缝试件（用高压水凿毛先浇界面）的直剪试验，以得到钢纤维特性以及浇筑方式对UHPC （直剪）初裂强度、峰值强度、破坏模式以及直剪承载力的影响；并基于试验结果及UHPC细观本构模型开展了UHPC直剪承载力的理论分析研究。结果表明：无纤维UHPC整体试件和钢纤维掺量未超过3.0%的平接缝试件直剪破坏模式均为脆性破坏，纤维掺量达到2.5%的整体试件具备剪切延性破坏的特征；纤维掺量达到2.5%的平接缝试件界面处新老UHPC结合紧密；整体界面和平接缝界面直剪的初裂强度与峰值强度均随纤维掺量增加而显著增加，且峰值强度随纤维掺量几乎呈线性变化；纤维形状与长径比对整体界面初裂强度和峰值强度的影响不大，对平接缝界面则长纤维优于短纤维，异形纤维优于平直形纤维；整体界面和平接缝界面直剪的峰裂比（峰值强度与初裂强度之比）为103.5%~166.7%，整体界面峰裂比均显著大于纤维掺量相同的平接缝界面，2种界面的峰裂比均随钢纤维掺量增加而增加。建立了平接缝界面与整体界面直剪峰值强度之比η（简称直剪强度比）与纤维特征参数λf之间的高精度拟合公式。此外，还分别提出了高精度的UHPC整体界面和平接缝界面的直剪承载力计算公式。
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| 关 键 词： | 桥梁工程 直接剪切性能 试验研究 湿接缝 超高性能混凝土(UHPC) 钢纤维特性 |
| 收稿时间： | 2021-01-13 |
Experimental Investigation and Calculation Method of UHPC Direct Shear Capacity |
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| FENG Zheng,LI Chuan-xi,PAN Ren-sheng,ZHOU Jia-le,KE Lu,KE Hong-jun.Experimental Investigation and Calculation Method of UHPC Direct Shear Capacity[J].China Journal of Highway and Transport,2021,34(8):78-90. |
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| Authors: | FENG Zheng LI Chuan-xi PAN Ren-sheng ZHOU Jia-le KE Lu KE Hong-jun |
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| Affiliation: | 1. Key Laboratory of Green Construction and Maintenance of Bridges and Buildings of Hunan Province, Changsha University of Science & Technology, Changsha 410004, Hunan, China;2. Key Laboratory of Safety Control for Bridge Engineering of the Ministry of Education, Changsha University of Science & Technology, Changsha 410004, Hunan, China;3. School of Civil Engineering and Architecture, Guangxi University, Nanning 530004, Guangxi, China |
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| Abstract: | Owing to the lack of studies on the direct shear performance of ultra-high performance concrete (UHPC), direct shear tests of 24 Z-shaped UHPC monolithic-casted and flat joint (with the first pouring interface roughened by high-pressure water) specimens were performed to assess the effects of steel fiber properties and casting methods on the initial cracking strength, peak strength, shear failure mode, and shear capacity of the UHPC (direct shear joint). Theoretical investigations were performed to predict the UHPC direct shear capacity based on the UHPC meso-scale constitutive model and test results. The obtained results indicate that the monolithic UHPC specimens without steel fibers, and the UHPC flat joint specimens with steel fiber content less than 3.0%, failed with typical brittle modes. The monolithic UHPC specimens exhibited ductile shear failure when the fiber volume fraction was 2.5%. The new and old UHPC at the interface of the UHPC flat joint specimens can bond tightly when the fiber volume fraction is approximately 2.5%. The direct shear initial cracking strength and peak strength of the monolithic interface and the flat joint interface both increased significantly with an increase in the fiber content, and the peak strength changed almost linearly with the fiber content. The shape and length-to-diameter ratio of the fiber had a negligible effect on the initial cracking and peak strength of the monolithic interface. However, for the UHPC flat joint specimens, the long fibers exhibited better performance than the short fibers in improving the direct shear strength, while the profiled fibers exhibited better performance than the straight fibers. The peak-to-crack ratios (the ratio of direct shear peak strength to cracking strength) of the monolithic and flat joint interfaces are in the range of 103.5%-166.7%, and the peak-to-crack ratio of the monolithic interface is significantly greater than that of the flat joint interface with the same fiber content. The peak-to-crack ratios of these two interfaces increased with an increase in fiber content. A high-precision fitting formula was established between the ratios of the direct shear peak strength of the flat joint interface to that of the monolithic interface η (referred to as the direct shear strength ratio), and the fiber characteristic parameter λf. In addition, high-precision formulas for calculating the direct shear capacity of the UHPC monolithic interface and flat joint interface were proposed. |
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| Keywords: | bridge engineering direct shear performance experimental investigation wet joint ultra high performance concrete (UHPC) steel fiber characteristic |
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