FRP加固受损RC梁受弯剥离承载力预测模型

Prediction Model for Debonding Bearing Capacity of Damaged Reinforced Concrete Beam Flexurally Strengthened with Fiber Reinforced Polymer

以纤维增强复合材料(FRP)片材加固受损钢筋混凝土(RC)梁为研究对象,探讨该类加固梁受弯中部剥离承载力的预测模型。通过建立加固梁弯曲主裂纹根部FRP-混凝土界面裂纹尖端的力学分析模型,基于断裂力学理论推导了界面裂纹能量释放率的计算公式;以界面断裂能作为剥离判据,提出了一种既考虑加固件弯剪内力的影响,又能直接计算中部界面剥离承载力的预测模型。制作了19根矩形RC梁,通过试验研究了损伤程度、剪跨比和碳纤维增强复合材料(CFRP)厚度等参量对加固梁剥离荷载的影响。结果表明:利用提出的计算模型可以较好预测CFRP加固RC梁的中部剥离破坏,预测结果偏安全;随着剪跨比的减小和CFRP厚度的增加,加固梁的抗剥离荷载明显提高,但当加固梁的剪跨比大于2.5时,其破坏模式并无明显变化;RC梁在受弯荷载作用后的既有损伤程度对CFRP加固后的抗剥离承载力影响不大。

With the damaged reinforced concrete （RC） beam flexurally strengthened with fiber reinforced polymer （FRP） laminates as the research object, the prediction model for intermediate debonding bearing capacity was investigated. A mechanical analysis model for the interface crack tip between FRP and concrete was established, which initiated from the root of the main flexural crack. Based on the fracture mechanics theory, a formula for calculation of the energy release rate of interface crack was derived. With the interface fracture energy as debonding criterion, a new prediction model for debonding bearing capacity of the strengthened beam was proposed, which not only took into account the effects of moment and shear force, but also could directly calculate the intermediate debonding bearing capacity. Moreover, in order to verify the proposed model, a total of 19 beams with rectangular section were tested. The test parameters included pre-damage levels of RC beams, ratio of shear span to depth and carbon fiber reinforced polymer （CFRP） thickness. The results show that the proposed model can safely and effectively predict the intermediate debonding bearing capacity of RC beam strengthened with FRP laminates. With the decrease of the shear span-depth ratio and the increase of CFRP thickness, the debonding load of strengthened beam increases, but the failure mode has no obvious change when the shear span- depth ratio is more than 2.5. The damage level Of pre-damage induced by flexural load has no obvious effect on the debonding bearing capacity of the RC beam strengthened with CFRP.