CFRP-钢复合筋与珊瑚海砂海水混凝土黏结性能试验研究

Experimental study on bond behavior between CFRP-steel composite bar and coral sea-sand seawater concrete

为研究碳纤维布包裹钢复合筋(CFRP-钢复合筋,简称“复合筋”)与珊瑚海砂海水混凝土(coral sea-sand seawater concrete,CSSC)的黏结性能,进行15组共45个黏结试件的单向拔出试验,得到复合筋与CSSC的界面黏结破坏机理,分析复合筋直径、黏结长度、保护层厚度、混凝土强度、混凝土及筋材种类对黏结性能的影响。试验结果表明:区别于钢筋,由于外覆层FRP抗剪性能差造成界面滑移后复合筋表面发生剪切损伤,界面层混凝土的破碎程度更小;随着复合筋直径及黏结长度的增大,界面的黏结强度逐渐降低;混凝土保护层小于4倍复合筋直径dc时,增大混凝土厚度可有效提高黏结强度,但混凝土保护层大于4dc后增强效果大幅减弱;与嵌入复合筋试件相比,嵌入相同直径钢筋试件的界面黏结强度增大了17.9%;与普通混凝土(NC)试件相比,CSSC试件的界面黏结强度增大了23.8%,但劈裂破坏界面上CSSC的粗骨料断裂程度远高于NC。基于试验结果及收集到的同类研究结果,提出了复合筋与CSSC的黏结强度计算式,其在大样本量下具有良好的计算精度,并通过确定界面黏结系数K的取值范围,建立临界锚固长度的计算式。为反映预测曲线的全过程,建议采用mBPE模型全面准确地描述复合筋与CSSC间的黏结应力-滑移关系。

In order to study the bond behavior between CFRP sheet wrapped steel composite bar(CFRP-steel composite bar,referred to as‘composite bar’)and coral sea-sand seawater concrete(CSSC),15 groups(a total of 45)bonding specimens were subjected to unilateral pull-out tests.The interface bonding failure mechanism of the composite bar and CSSC was revealed,and the influence of composite bar diameter,bonding length,cover thickness,concrete strength,concrete and reinforcement type on the bonding performance was analyzed.The test results show that unlike the steel bar,the shear damage occurs on the surface of the composite bar after sliding due to the poor shear resistance of the outer covering FRP,and the degree of breakage of the concrete in the interface layer is smaller.With the increase of composite bar diameter and bonding length,the bond strength of the interface decreases gradually.When the concrete cover is less than four times the diameter of the composite bar(dc),increasing the concrete thickness can effectively improve the bond strength,but the strengthening effect is greatly weakened after the concrete cover is more than 4dc.Compared with the specimens embedded with composite bar,the bond strength of the 243 specimens embedded with the same diameter of steel bar increases by 17.9%.Compared with natural concrete(NC)specimens,the bond strength of CSSC specimens increases by 23.8%,but the fracture degree of coarse aggregate of CSSC at the splitting interface is much higher than that of NC specimens.Based on the test results and collected similar research results,a formula for calculating the bond strength between composite bar and CSSC was proposed,which shows good calculation accuracy in large sample size.By determining the value range of bond coefficient K,a formula for calculating the critical anchorage length was established.To reflect the entire process of predicting the curve,it is recommended to use the mBPE model to accurately describe the bond stress-slip relationship between composite bar and CSSC in this paper.