EXPERIMENTAL RESEARCH ON THE BOND BEHAVIOR OF GFRP BARS IN BFRP-CONFINED CONCRETE
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摘要: 通过对36个拉拔试件进行试验,对玻璃纤维复材(GFRP)筋与玄武岩纤维复材(BFRP)侧向约束混凝土的黏结性能进行研究。试验变量包括4种BFRP侧向约束层数(0,1,2,3层)和3种混凝土强度(40.6,44.2,52.7 MPa)。试验结果表明:BFRP侧向约束混凝土可使拉拔试件的破坏模式由脆性的劈裂破坏转变为延性的拔出破坏;BFRP侧向约束可显著提升GFRP筋与混凝土之间的黏结性能;较于无约束试件,3种混凝土强度下,1层、2层和3层BFRP约束试件的黏结强度分别提高了25%~35%、42%~56%、52%~88%,达到黏结强度时的平均黏结滑移量分别增大了47%~187%、86%~267%、168%~211%;当约束试件的黏结应力大约达到无约束试件的黏结强度时,BFRP外约束才逐渐开始发挥作用,且达到黏结强度时的BFRP径向约束应力基本随着BFRP约束层数和混凝土强度的提高而提高;同一混凝土强度下,约束试件的相对黏结强度随着BFRP约束刚度比的增大而近似呈线性增大。Abstract: The bond behavior of GFRP bar in BFRP-confined concrete was experimentally investigated. 36 specimens were prepared for pull-out test. The test variables included the number of BFRP layers (0, 1, 2 and 3 layers of fiber fabric) and the compressive strength of concrete (40.6, 44.2 and 52.7 MPa). The test results indicated that for BFRP lateral confinement, the typical failure mode of specimens was changed from brittle splitting failure to ductile pull-out failure. The bond behavior between GFRP bars and concrete could be significantly improved due to the lateral confinement from the BFRP jacket. Compared with unconfined specimens, bond strength of confined specimens with one, two and three layers of BFRP increased by 25%~35%, 42%~56% and 52%~88%, respectively, corresponding to three different concrete strengths, and the average bond slip of FRP bars reaching to the bond strength increased by 47%~187%, 86%~267%, 168%~211%, respectively. The confinement from the outer BFRP jacket was activated when the bond stress of confined specimens approximately reached the bond strength of unconfined specimens. The radial confining stress corresponding to bond strength increased with the number of BFRP layers and the concrete strength. Under the same concrete strength conditions, the normalized bond strength of confined specimens approximately linearly increased with the increase of confinement stiffness ratio of BFRP.
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Key words:
- FRP bar /
- bond behavior /
- confined concrete /
- bond stress-slip relationship /
- confining stress
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