| 预应力NSM CFRP抗剪加固钢筋混凝土T梁试验 |
| |
| 引用本文： | 彭晖,郭恒良,钟正强,粟淼,陈辉,黄敦文.预应力NSM CFRP抗剪加固钢筋混凝土T梁试验[J].中国公路学报,2022,35(2):159-168. |
| |
| 作者姓名： | 彭晖 郭恒良 钟正强 粟淼 陈辉 黄敦文 |
| |
| 作者单位： | 1. 长沙理工大学 土木工程学院, 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 |
| |
| 基金项目： | 国家自然科学基金项目(51578078，51878068，52178186，52008036)；湖南省科技创新计划项目(2020RC2052)； 湖南省研究生科研创新项目(QL20210207) |
| |
| 摘 要： | 大跨径预应力混凝土梁桥易因竖向预应力损失等导致抗剪性能不足,引起腹板斜裂缝和梁体下挠等病害。为提高混凝土梁桥的斜截面承载和抗裂性能,提出了表层嵌贴(NSM)预应力CFRP加固钢筋混凝土梁腹板的方法,研发了专用夹具及张拉锚固装置,并实现了预应力NSM CFRP对钢筋混凝土T梁腹板的抗剪加固。在此基础上,进行了4根预应力NSM CFRP抗剪加固RC T梁静载试验,考察了各试件的受力行为和破坏模式,研究了试件斜裂缝形态变化规律,分析了试件箍筋、CFRP和混凝土的抗剪贡献。试验结果表明:预应力NSM CFRP抗剪加固可显著提高试件的腹板斜截面开裂荷载和抗剪承载力,但CFRP黏结端部混凝土同时承受预应力放张和荷载引起的应力,更容易发生腹板混凝土保护层剥离破坏,削弱预应力CFRP抗剪加固效果,应考虑增设碳纤维U形箍锚固等措施;预应力加固试件的临界斜裂缝角度增加,使与临界斜裂缝相交的CFRP数量减小,但斜裂缝发展速率和临界斜裂缝宽度得到有效抑制;预应力CFRP放张引起的压应力降低了腹板混凝土主拉应力,使临界斜裂缝高度显著减小,梁顶未开裂混凝土能承担更多剪力;极限状态下预应力加固试件的CFRP抗剪贡献小于无预应力加固试件,但混凝土抗剪贡献却显著提高,试件抗剪承载力提升实质是混凝土抗剪能力增大。
|
| 关 键 词： | 桥梁工程 抗剪加固 静载试验 NSM CFRP 预应力 剥离破坏 |
| 收稿时间： | 2021-07-15 |
Experimental Study on T-section RC Beams Shear-strengthened with Prestressed NSM CFRP |
| |
| PENG Hui,GUO Heng-liang,ZHONG Zheng-qiang,SU Miao,CHEN Hui,HUANG Dun-wen.Experimental Study on T-section RC Beams Shear-strengthened with Prestressed NSM CFRP[J].China Journal of Highway and Transport,2022,35(2):159-168. |
| |
| Authors: | PENG Hui GUO Heng-liang ZHONG Zheng-qiang SU Miao CHEN Hui HUANG Dun-wen |
| |
| Affiliation: | 1. School of Civil Engineering, Changsha University of Science and Technology, Changsha 410004, Hunan, China;2. Key Laboratory of Safety Control of Bridge Engineering of Ministry of Education, Changsha University of Science and Technology, Changsha 410004, Hunan, China |
| |
| Abstract: | Owing to the loss of vertical prestress and other factors, long-span prestressed concrete beam bridges are prone to lack of shear performance, resulting in problems such as shear cracks in the web and excessive deflection of the girder. In this study, a method of shear strengthening with prestressed near surface mounted (NSM) carbon fiber reinforced polymer (CFRP) was proposed to improve the shear capacity and shear crack resistance of concrete beam bridges. Moreover, a special tensioning and anchoring device was developed to achieve shear strengthening of reinforced concrete (RC) T-beams with prestressed NSM CFRP. Four RC T-beams shear strengthened with prestressed NSM CFRP were tested, and their mechanical behavior and failure mode were investigated. In addition, the variation law of shear cracks in the T-beams was studied, and the shear contributions of the stirrup, CFRP, and concrete were analyzed. The test results show that prestressed NSM CFRP shear strengthening can significantly increase the shear cracking load and shear capacity. Concrete at the bonded end of CFRP bears the stress caused by the prestressing tension and load simultaneously. Hence, the concrete is more prone to debond at the concrete cover of the web, which weakens the shear strengthening effect of prestressed CFRP. To avoid this failure mode, anchorage systems, such as U-shaped CFRP sheets, should be considered. When the specimens were strengthened with prestressed NSM CFRP, the angle of the critical shear crack increases significantly, reducing the number of CFRP intersecting with the critical shear crack. However, the development rate and width of the critical shear crack are effectively restrained. Because the compressive stress caused by prestressed CFRP releasing reduces the principal tensile stress of the web concrete in specimens with shear strengthening, the height of the critical shear crack decreases significantly, and the uncracked concrete at the top of the beam can bear more shear load. Under the ultimate load, the shear contribution of CFRP in specimens strengthened with prestressed CFRP is smaller than that of the non-prestressed strengthening specimens. However, the shear contribution of concrete is significantly improved, increasing the shear capacity of specimens. |
| |
| Keywords: | bridge engineering shear strengthening static experiment NSM CFRP prestress debonding failure |
|
| 点击此处可从《中国公路学报》浏览原始摘要信息 |
|
点击此处可从《中国公路学报》下载全文 |
|
