反复荷载下低强度混凝土与光圆钢筋局部黏结性能的试验研究
|
摘要
通过反复拉拔试验研究了不同加载阶段下光圆钢筋在低强度混凝土中黏结应力沿黏结长度的分布。根据试验中得到的光圆钢筋在低强度混凝土中的局部应力-应变关系及荷载-滑移关系推算出了沿黏结长度拉应力、黏结应力的分布曲线及局部黏结应力-相对滑移关系,并在试验研究基础上,推导了各加载阶段光圆钢筋与低强度混凝土间黏结应力分布的变化机理。试验中采用了3个黏结长度分别为10D、15D、20D(D为钢筋直径)的中心拔出试件。研究结果表明:早期加载阶段,黏结应力起始于加载端,随着荷载增大黏结应力的峰值点由加载端逐渐向自由端移动,并且钢筋表面分布的黏结应力从加载端开始,从由胶结力提供迅速转变为界面摩擦力提供;随着自由端的钢筋滑移量被记录后,分布在钢筋表面的胶结力全部消失;进入卸载阶段至荷载降为0时,由于钢筋黏结段区域存在的残留拉应力,观察到分布的残留黏结应力呈现为反对称形;随后,即使进入反复加载阶段,黏结应力的分布特征基本保持不变。另外,所有试件各测点对应的局部黏结应力-相对滑移曲线与平均黏结应力-滑移曲线的滞回特性基本一致。
In this study,the bond stress distributions between low strength concrete and plain round bars along bond length in different loading phases were studied.Based on the experimental results of local stress-strain and load-slip relations between plain round bars and low strength concrete,the tensile stress,the bond stress distributions and the relationship between local bond stress and relative slip were obtained.Variation mechanism was of bond stress distributions between low strength concrete and plain round bars were derived due to the experimental research in different loading phases.Plain round bar was embedded in the center of concrete prism,and three lengths of embedment were prepared at 10 D、15 D and 20 D(D:the diameter of the bar)in this test.From the test results,bond stress started to occur from the loaded end in the early phase.The location of the peak bond stress shifted from the loaded end toward to the unloaded end of the bar with increasing applied load.Bond stress along the bar which was provided by the adhesion force rapidly vanished and the friction force occurred from the loaded end;Adhesive force vanished along the bar when slip at the unloaded end was measured;Distributions of the bond stress along the bar were observed to an anti-symmetric shape due to the residual tensile stress along the bar in the unloaded phase;Subsequently,even though the applied load was reversed,bond stress distribution along the bar was still constant.In addition,the hysteric characteristics of the local bond stress-relative slip curves were almost similar to the hysteric characteristics of the average bond stress-slip curve regardless of the bond length of the specimens.
In this study,the bond stress distributions between low strength concrete and plain round bars along bond length in different loading phases were studied.Based on the experimental results of local stress-strain and load-slip relations between plain round bars and low strength concrete,the tensile stress,the bond stress distributions and the relationship between local bond stress and relative slip were obtained.Variation mechanism was of bond stress distributions between low strength concrete and plain round bars were derived due to the experimental research in different loading phases.Plain round bar was embedded in the center of concrete prism,and three lengths of embedment were prepared at 10 D、15 D and 20 D(D:the diameter of the bar)in this test.From the test results,bond stress started to occur from the loaded end in the early phase.The location of the peak bond stress shifted from the loaded end toward to the unloaded end of the bar with increasing applied load.Bond stress along the bar which was provided by the adhesion force rapidly vanished and the friction force occurred from the loaded end;Adhesive force vanished along the bar when slip at the unloaded end was measured;Distributions of the bond stress along the bar were observed to an anti-symmetric shape due to the residual tensile stress along the bar in the unloaded phase;Subsequently,even though the applied load was reversed,bond stress distribution along the bar was still constant.In addition,the hysteric characteristics of the local bond stress-relative slip curves were almost similar to the hysteric characteristics of the average bond stress-slip curve regardless of the bond length of the specimens.
引文
[1] 李翔,顾祥林.碳纤维布加固低强度混凝土梁的抗弯承载力[J].土木工程学报,2012,45(1):24-29. Li Xiang,Gu Xianglin.Bending bearing capacity of low strength reinforced concrete beams and strengthened with carbon fiber composite sheets[J].China Civil Engineering Journal,2012,45(1):24-29.(in Chinese)
[2] Hideo,Araki.and Hayato,IKI (2011);Strength of RC Column with low strength and plain round bars,fib Symposium,Prague,Czech Republic.
[3] Abrams D A.1913.Tests of Bond Between Concrete and Steel,University of Illinois Bulletin No.71,University of Illinois at Urbana-Champaign,Ulbana.IL.
[4] Watstein D.Distribution of Bond Stress in Concrete Pull-out Specimens[C].Journal Proceedings,1949,18(11):1041-1052.
[5] Mains R M.Measurement of the Distribution of Tensile and Bond Stresses Along Reinforcing Bars[J].Journal.of ACI,1951,23(5):225-252.
[6] Jiang D H,Shan S P,Andonian A T.Study of the transfer of tensile forces by bond[J].ACI Journal Proceedings,1984,81(3):251-259.
[7] Mizuno T,Watanabe A.on the bond stress distribution along round bars,deformed bars and twisted deformed bars[J].Journal of Japan Society of Civil Engineering,1963,93:23-30.
[8] Araki H,Kagawa J.Bond Strength of Plain Round Bars Repaired by Epoxy Resin Injection[C].IASE Symposium Report.International Associcotion for Bridge and Structural Engineering,2010,97(12):56-63.
[9] Verderame G M,Ricci P,De Carlo G,et al.Cyclic bond behaviour of plain bars[J].Part I:Experimental investigation,2009,3499-3511,Part II:Analytical investigation,3512-3522,Construction and Building Materials 23.
[10] 王玉新.反复荷载作用下锈蚀钢筋与混凝土黏结滑移研究[D].郑州:华北水利水电大学,2012. Wang Yuxin.Investigation on bond-slip relationship between corroded steel bars and concrete under cyclic loading[D].Zhengzhou:North China University of Water Resources and Electric Power,2012.(in Chinese)
[11] Morita S,Sumi T.Bond-slip relationship under repeated loading[J],Transactions of the Architectural Institute of Japan,1975,229:15-24.
[12] Feldman L R,Bartlett F M.Bond stresses along plain steel reinforcing bars in pullout specimens[J].ACI Structural Journal,2007,104(6):685-692.
[2] Hideo,Araki.and Hayato,IKI (2011);Strength of RC Column with low strength and plain round bars,fib Symposium,Prague,Czech Republic.
[3] Abrams D A.1913.Tests of Bond Between Concrete and Steel,University of Illinois Bulletin No.71,University of Illinois at Urbana-Champaign,Ulbana.IL.
[4] Watstein D.Distribution of Bond Stress in Concrete Pull-out Specimens[C].Journal Proceedings,1949,18(11):1041-1052.
[5] Mains R M.Measurement of the Distribution of Tensile and Bond Stresses Along Reinforcing Bars[J].Journal.of ACI,1951,23(5):225-252.
[6] Jiang D H,Shan S P,Andonian A T.Study of the transfer of tensile forces by bond[J].ACI Journal Proceedings,1984,81(3):251-259.
[7] Mizuno T,Watanabe A.on the bond stress distribution along round bars,deformed bars and twisted deformed bars[J].Journal of Japan Society of Civil Engineering,1963,93:23-30.
[8] Araki H,Kagawa J.Bond Strength of Plain Round Bars Repaired by Epoxy Resin Injection[C].IASE Symposium Report.International Associcotion for Bridge and Structural Engineering,2010,97(12):56-63.
[9] Verderame G M,Ricci P,De Carlo G,et al.Cyclic bond behaviour of plain bars[J].Part I:Experimental investigation,2009,3499-3511,Part II:Analytical investigation,3512-3522,Construction and Building Materials 23.
[10] 王玉新.反复荷载作用下锈蚀钢筋与混凝土黏结滑移研究[D].郑州:华北水利水电大学,2012. Wang Yuxin.Investigation on bond-slip relationship between corroded steel bars and concrete under cyclic loading[D].Zhengzhou:North China University of Water Resources and Electric Power,2012.(in Chinese)
[11] Morita S,Sumi T.Bond-slip relationship under repeated loading[J],Transactions of the Architectural Institute of Japan,1975,229:15-24.
[12] Feldman L R,Bartlett F M.Bond stresses along plain steel reinforcing bars in pullout specimens[J].ACI Structural Journal,2007,104(6):685-692.