考虑二次受力的内嵌BFRP筋加固混凝土T形梁受剪性能试验研究
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摘要
为了研究二次受力对内嵌BFRP筋加固混凝土梁受剪性能的影响,对6根内嵌BFRP筋混凝土T形截面加固梁和2根对比梁进行了受剪性能试验。对试件梁的受力过程、破坏模式、荷载-挠度曲线、荷载-应变曲线、斜截面应力重分布现象以及初始荷载大小、卸载程度和BFRP筋端部锚固长度等因素对加固梁的影响进行研究。研究结果表明:虽然加固梁发生了剪切破坏,但是破坏特征复杂且伴随着次生破坏;试件梁的斜截面在斜裂缝出现时和箍筋屈服时出现了重分布,对于二次受力试件梁,BFRP筋应变滞后现象明显,且BFRP筋应变分布不均匀,在进行加固梁承载力计算时应考虑此因素带来的承载力降低的影响;初始荷载、卸载程度及BFRP筋端部锚固有利于加固梁极限荷载的提高和延缓斜裂缝的开展,应在加固梁受剪承载力计算公式中引入相关系数或满足构造要求来体现这些因素的影响。
A total of six RC T-beams strengthened with near-surface mounted (NSM) BFRP bars and two control beams in shear were conducted to investigate the effect of secondary loading on the shear behavior of the strengthened beam. The loading process, failure mode of the strengthened beams,load-deformation relationship, load-strain relationship,stress redistribution in inclined section,and the influence factors including initial load,the degree of unloading and embedded length at the end of BFRP bars were studied. The experimental results show that the shear failure of the strengthened beams is complicated and accompanied by secondary failure. When the diagonal crack appears and the stirrup yields,the stress redistribution in inclined section occurs. For the specimen subjected to secondary loading,the strain lag of BFRP bars is obvious,and the strain distribution of BFRP bars is uneven. The effect of the strain lag on the decrease of bearing capacity of the strengthened beam should be considered. The initial load,the magnitude of unloading and the appropriate embedded length at the end of BFRP bars in the flange are beneficial to improve the ultimate load and to delay the crack development. The correlation coefficient should be introduced in the calculation of the shear bearing capacity of the strengthened beam and the requirements of construction details should be satisfied,which reflect the influence of these factors.
A total of six RC T-beams strengthened with near-surface mounted (NSM) BFRP bars and two control beams in shear were conducted to investigate the effect of secondary loading on the shear behavior of the strengthened beam. The loading process, failure mode of the strengthened beams,load-deformation relationship, load-strain relationship,stress redistribution in inclined section,and the influence factors including initial load,the degree of unloading and embedded length at the end of BFRP bars were studied. The experimental results show that the shear failure of the strengthened beams is complicated and accompanied by secondary failure. When the diagonal crack appears and the stirrup yields,the stress redistribution in inclined section occurs. For the specimen subjected to secondary loading,the strain lag of BFRP bars is obvious,and the strain distribution of BFRP bars is uneven. The effect of the strain lag on the decrease of bearing capacity of the strengthened beam should be considered. The initial load,the magnitude of unloading and the appropriate embedded length at the end of BFRP bars in the flange are beneficial to improve the ultimate load and to delay the crack development. The correlation coefficient should be introduced in the calculation of the shear bearing capacity of the strengthened beam and the requirements of construction details should be satisfied,which reflect the influence of these factors.
引文
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[14]徐明磊.嵌入式FRP加固预裂混凝土梁的实验研究[D].沈阳:东北大学,2013:31-38.(XU Minglei.Experimental research on reinforced concrete beams retrofitted with near surface mounted FRP reinforcement[D].Shenyang:Northeastern University,2013:31-38.(in Chinese))
[15]杨汝俊,鲍林,孙凯.FRP加固二次受力RC约束梁抗剪性能对比试验探析[J].工程质量,2016,34(6):21-25.(YANG Rujun,BAO Lin,SUN Kai.Comparative test analysis over shear performance of FRPreinforcement secondary load RC restrained beams[J].Construction Quality,2016,34(6):21-25.(in Chinese))
[16]张玉成.碳纤维布加固钢筋混凝土梁抗剪性能研究[D].武汉:武汉大学,2005:19-24.(ZHANGYucheng.Study on shear behaviors of reinforced concrete beam strengthened with CFRP sheet[D].Wuhan:Wuhan University,2005:19-24.(in Chinese))
[2]岳清瑞,李庆伟,杨勇新.纤维增强复合材料嵌入式加固技术[J].工业建筑,2004,34(4):1-4.(YUEQingrui,LI Qingwei,YANG Yongxin.Technique of structures strengthened with near surface mounted FRP[J].Industrial Construction,2004,34(4):1-4.(in Chinese))
[3]LORENZIS De L,TENG J G.Near-surface mounted FRP reinforcement:an emerging technique for strengthening structures[J].Composites:Part B,2007,38:119-143.
[4]BARROS J A O,DIAS S J E.Near surface mounted CFRP laminates for shear strengthening of concrete beams[J].Cement&Concrete Composites,2006,28(3):276-292.
[5]DIAS S J E,BARROS J A O.Performance of reinforced concrete T beams strengthened in shear with NSM CFPRlaminates[J].Engineering Structures,2010,32(2):373-384.
[6]RIZZO A,LORENZIS De L.Behavior and capacity of RC beams strengthened in shear with NSM FRPreinforcement[J].Construction&Building Materials,2009,23(4):1555-1567.
[7]HASKETT M,OEHLERS D J,ALI M S M,SHARMAS K.Evaluating the shear-friction resistance across sliding planes in concrete[J].Engineering Structures,2011,33:1357-1364.
[8]AI-MAHMOUD F,CASTEL A.Reinforced concrete beams strengthened with NSM CFRP rods in shear[J].Advances in Structural Engineering,2015,18(10):1563-1574.
[9]MOFIDI A,CHAALLAL O,CHENG L J,et al.Investigation of near surface-mounted method for shear rehabilitation of reinforced concrete beams using fiber reinforced-polymer composites[J].Journal of Composites for Construction,2016,20(2):1-14.
[10]贾庆扉.混凝土梁表层嵌贴CFRP板条的抗剪加固试验研究[D].杭州:浙江大学,2006:28-45.(JIAQingfei.Experimental study on RC beams shear strengthened with NSM strips[D].Hangzhou:Zhejiang University,2006:28-45.(in Chinese))
[11]刘国瑞.表面内嵌FRP加固混凝土梁抗剪性能研究[D].沈阳:沈阳建筑大学,2012:32-44.(LIUGuorui.Study on shear behavior of concrete beams strengthened with near surface mounted FRP[D].Shenyang:Shenyang Jianzhu University,2012:32-44.(in Chinese))
[12]JALALI M,SHARBATDAR MK,CHEN J F,et al.Shear strengthening of RC beams using innovative manually made NSM FRP bars[J].Construction and Building Materials,2012,36:990-1000.
[13]宗周红,程怡,黄学漾,等.CFRP板加固RC&PPC梁抗剪性能试验研究[J].工程力学,2013,30(6):236-246.(ZONG Zhouhong,CHENG Yi,HUANGXueyang,et al.Experimental study on shear properties of reinforced concrete(RC)and partial prestressed concrete(PPC)beams strengthened with externally bonded CFRP strips[J].Engineering Mechanics,2013,30(6):236-246.(in Chinese))
[14]徐明磊.嵌入式FRP加固预裂混凝土梁的实验研究[D].沈阳:东北大学,2013:31-38.(XU Minglei.Experimental research on reinforced concrete beams retrofitted with near surface mounted FRP reinforcement[D].Shenyang:Northeastern University,2013:31-38.(in Chinese))
[15]杨汝俊,鲍林,孙凯.FRP加固二次受力RC约束梁抗剪性能对比试验探析[J].工程质量,2016,34(6):21-25.(YANG Rujun,BAO Lin,SUN Kai.Comparative test analysis over shear performance of FRPreinforcement secondary load RC restrained beams[J].Construction Quality,2016,34(6):21-25.(in Chinese))
[16]张玉成.碳纤维布加固钢筋混凝土梁抗剪性能研究[D].武汉:武汉大学,2005:19-24.(ZHANGYucheng.Study on shear behaviors of reinforced concrete beam strengthened with CFRP sheet[D].Wuhan:Wuhan University,2005:19-24.(in Chinese))
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