胶层厚度对CFRP布加固RC梁抗弯承载力影响研究

Influence of adhesive thickness on the flexural capacity of reinforced concrete beams strengthened with CFRP sheets

为研究黏结胶层厚度对CFRP布外贴加固有预损伤的钢筋混凝土梁抗弯承载力的影响,对已有纤维片材加固混凝土试件的黏结胶层厚度控制方法进行改进,完成2根基准对比梁和4根损伤加固梁的抗弯试验,并采用有限元软件ABAQUS分别建立三维实体模型和纤维梁模型对试验进行数值模拟。研究结果表明:当黏结胶层厚度从0.5 mm增至3 mm时,试件的极限抗弯承载力和对应的极限挠度分别增大18.3%和44.8%。黏结界面的剥离荷载随黏结胶层厚度增大而增大。当黏结胶层厚度从0.5 mm增至2 mm时,黏结界面的剥离荷载小于碳纤维布的断裂荷载,试件的失效形式仍为黏结界面剥离。当黏结胶层厚度增至3 mm时,黏结界面的剥离荷载超过碳纤维布的断裂荷载,试件的失效形式转为CFRP布断裂。随着黏结胶层厚度增大,界面的有效黏结长度增加,应力分布趋于均匀,局部应力集中放缓,CFRP-混凝土界面的黏结性能随之增强。在需要大量计算的非线性分析中,合理地建立纤维梁有限元模型可在满足分析精度的基础上大幅提升计算求解速度。

To study the influence of adhesive thickness on the flexural capacity of damaged reinforced concrete(RC) beams strengthened by carbon fiber reinforced plastic(CFRP) sheets, the adhesive thickness control method for RC specimens strengthened by fiber sheets was proposed. The flexural tests of 2 reference beams and 4damaged reinforced beams were conducted, while three-dimensional solid models and fiber beam models for numerical simulation of the experiment were established respectively by finite element software. The results indicate that when the adhesive thickness increases from 0.5 mm to 3 mm, the ultimate flexural capacity and ultimate deformation of the specimen increases by 18.3% and 44.8%. The debonding load of bonding interface increases with the increasement of the adhesive layer thickness. The debonding load of bonding interface is lower than the fracture load of CFRP sheet when the adhesive thickness increases from 0.5 mm to 2 mm. The failure mode of specimen is debonding of bonding interface. The debonding load of bonding interface exceeds the fracture load of CFRP sheet when the adhesive thickness increases to 3 mm, thus, the failure mode of specimen is fracture of CFRP sheet. As the thickness of the adhesive layer increases, the effective bonding length of the interface extends, while the stress distribution tends to be homogeneous and the local stress concentration mitigates, leading to the enhancement of the CFRP-concrete interface bonding performance. For nonlinear analysis that requires massive calculation, an appropriate finite element model of fiber beam can greatly improve the computational efficiency, as well as meeting the requirements of analytical accuracy.