基于UHPC的RC梁抗扭加固新方法及试验  

Experimental Investigation of a Novel Torsional Strengthening Strategy for RC Beams Based on UHPC

作　　者：周聪 汪建群[1,2] 陈继涛 邵旭东[3] 李立峰[3] 祝明桥[1,2] ZHOU Cong;WANG Jian-qun;CHEN Ji-tao;SHAO Xu-dong;LI Li-feng;ZHU Ming-qiao(Hunan Provincial Key Laboratory of Structures for Wind Resistance and Vibration Control,Hunan University of Science and Technology,Xiangtan 411201,Hunan,China;School of Civil Engineering,Hunan University of Science and Technology,Xiangtan 411201,Hunan,China;School of Civil Engineering,Hunan University,Changsha 410082,Hunan,China)

机构地区：[1]湖南科技大学结构抗风与振动控制湖南省重点实验室,湖南湘潭411201 [2]湖南科技大学土木工程学院,湖南湘潭411201 [3]湖南大学土木工程学院,湖南长沙410082

出　　处：《中国公路学报》2023年第9期119-133,共15页China Journal of Highway and Transport

基　　金：国家自然科学基金项目(52108140,52278176,51978257);湖南省自然科学基金项目(2021JJ40213,2020JJ4310);湖南省教育厅青年项目(21B0497)。

摘　　要：超高性能混凝土(Ultra-high Performance Concrete,UHPC)具有远超常规混凝土的力学性能及耐久性,十分适用于既有RC梁加固,但目前相关研究主要集中于抗弯和抗剪加固方面,关于抗扭加固的文献很少。为探究采用UHPC对RC梁进行抗扭加固的有效性,开展了9根试件的纯扭模型试验,包括1根未加固RC梁(对比梁)和8根UHPC加固RC梁,变化参数为UHPC层包裹方式、UHPC层厚度、UHPC掺加钢纤维类型、UHPC-RC界面处理方式以及UHPC层配筋率。基于模型试验,获得了各试件的扭转破坏模式、扭矩-扭率曲线、扭矩-应变曲线、裂缝分布、UHPC-RC界面滑移等结果,深入分析了不同参数对加固梁抗扭性能的影响规律。结果表明:加固梁的开裂和极限扭矩均明显高于对比梁,最大提升幅度分别为488.5%和593.2%;全包裹形式能更好地抵抗扭转效应,加固效果最佳,建议优先采用;两面包裹形式的抗扭承载力增幅最小,且试件破坏时UHPC层几乎从RC梁剥离,应避免采用;U形包裹形式的加固效果介于两面和全包裹之间,UHPC层与RC梁始终黏结良好,当全包裹无法实现时也可采用该形式;UHPC层厚度需综合考虑加固效果、加固成本以及加固梁尺寸要求来确定;掺端钩纤维加固梁的抗扭承载力优于掺圆直纤维试件;浇筑UHPC前应对RC梁表面作凿毛处理,以确保二者持续作为整体共同受力;UHPC层内配筋加固梁的抗扭承载力比未配筋时提高347.2%,增幅明显,建议在实际加固中使用。最后,提出了UHPC加固RC矩形梁的抗扭承载力计算公式,并对6根试件进行了验证,结果表明计算公式精度良好。Ultra-high-performance concrete(UHPC)exhibits superior mechanical performance and durability compared to normal concrete;thus,it is suitable for strengthening reinforced concrete(RC)beams.However,the existing literature mainly focuses on flexural and shear strengthening,and relevant research on torsional strengthening is insufficient.To investigate the feasibility of strengthening RC beams using UHPC,pure-torsion tests were conducted on nine specimens,including one unstrengthened RC beam(the control beam)and eight UHPC-strengthened RC beams.The variables considered for the investigation included the wrapping form of the UHPC layer,thickness of the UHPC layer,shape of the steel fibers added to the UHPC layer,UHPC-RC interfacial treatment,and steel reinforcement ratio of the UHPC layer.Based on the torsion tests,the torsional failure modes,torque-twist curves,torque-strain curves,distribution of cracks,and UHPC-RC interfacial slippage were acquired,and the effects of the considered variables on the torsional performance were systematically investigated.The results showed that the cracking and ultimate torques of all strengthened beams were higher than those of the control beam,with maximum increases of 488.5%and 593.2%,respectively.The full wrapping form could resist the external torque more effectively;thus,the beam strengthened using this form achieved the best strengthening efficiency.Therefore,this wrapping scheme is preferred for strengthening RC beams.By contrast,the beam strengthened using a 2-sided wrapping form exhibited the lowest strengthening efficiency.In addition,the two UHPC layers peeled almost entirely from the RC beam when the specimen was damaged.Therefore,this wrapping scheme should be avoided during torsional strengthening.The strengthening efficiency of the U-shaped form was between those of 2-sided and full wrapping forms,and no obvious slippage was observed at the UHPC-RC interface during the entire loading process.When the original beam could not be fully wrapped,a 3-sided wrapping form was

关 键 词：桥梁工程 抗扭加固 试验研究 超高性能混凝土 RC矩形梁 

分 类 号：U444[建筑科学—桥梁与隧道工程]