Effects of fiber content and concrete cover on the local bond behavior of helically ribbed GFRP bar and UHPC
Effects of fiber content and concrete cover on the local bond behavior of helically ribbed GFRP bar and UHPC
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DOI：
10.1016/j.jobe.2023.107939
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发表时间：
2023-10
影响因子：
6.4
通讯作者：
Rensheng Pan;Jiayao Zou;Peng Liao;Shuai Dong;Jihua Deng
中科院分区：
文献类型：
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作者：
Rensheng Pan;Jiayao Zou;Peng Liao;Shuai Dong;Jihua Deng
GFRP筋与UHPC的粘结性能是GFRP加固UHPC构件和结构中的一个重要问题。通过对45个试件的拉拔试验，研究了螺旋肋GFRP筋与超高性能混凝土（UHPC）的局部粘结破坏模式、粘结强度和粘结应力-滑移曲线。试验参数包括UHPC中纤维含量Vf（0%-3%）和混凝土保护层C（12-66 mm），并评估其对局部粘结性能的影响。C ≥ 36 mm和Vf≥ 2%的试件倾向于表现为直接拔出破坏，而C < 36 mm和Vf<2%的试件则多表现为劈拉破坏。直径为18 mm的GFRP筋与UHPC的粘结强度为18.76- 54.11MPa。在一定范围内，增加UHPC中纤维含量或增加保护层厚度，可以显著提高粘结强度。随着纤维掺量从0%增加到2%，GFRP筋与UHPC的粘结强度提高了74.81%~ 92.22%。然而，当纤维含量从2%进一步增加到3%时，粘结强度显示几乎可以忽略不计的增长。在覆盖层厚度对粘结强度的影响中观察到类似的现象。当埋置长度Le =D时，临界保护层厚度约为钢筋直径D的3倍。此外，这两个因素对粘结性能的影响存在一定的交互作用。基于试验结果，提出了考虑纤维掺量影响的UHPC中GFRP筋粘结强度预测公式。进一步建立了GFRP筋与UHPC之间粘结滑移关系的拟合模型。
The bond performance of GFRP bar to UHPC is of great concern in GFRP reinforced UHPC elements and structures. In this study, pullout tests were conducted on 45 specimens to investigate the local bond behavior of helically ribbed GFRP bar to UHPC which was characterized by the failure mode, the bond strength and the bond stress-slip curve. The test parameters included the fiber content in UHPC Vf(0 %–3 %) and the concrete cover C (12–66 mm) and their effects on the local bond behavior were accessed. Specimens with C ≥ 36 mm and Vf≥ 2 % trended to exhibit the direct pullout failure while those specimens with C < 36 mm and Vf< 2 % generally behaved in the splitting pullout failure. GFRP bars with diameter of 18 mm embedded in UHPC had the bond strength of 18.76–54.11 MPa. The bond strength could be significantly enhanced by increasing the fiber content in UHPC or the cover thickness within a certain range. As the fiber content increased from 0 % to 2 %, the bond strength of GFRP bar to UHPC grew by 74.81 %–92.22 %. However, the bond strength showed almost negligible growth when the fiber content further increased from 2 % to 3 %. Similar phenomenon was observed in the effect of cover thickness on the bond strength. The critical cover thickness was found to be approximate 3 times of rebar diameterDin the case of embedment lengthLe=D. In addition, some interactions were observed in the effects of these two factors on the bond performance. Based on the test results, an updated equation including the influence of fiber content was proposed to predict the bond strength of ribbed GFRP bars embedded in UHPC. Further, a fitted model was developed to describe bond-slip relationship between GFRP bars and UHPC.