Ph.D. Student at Civil Engineering Department, College of Engineering, University of Sulaimani, Sulaymaniyah, Iraq.
Professor at Civil Engineering Department, College of Engineering, University of Sulaimani, Sulaymaniyah, Iraq.
PLoS One. 2021 Dec 30;16(12):e0261290. doi: 10.1371/journal.pone.0261290. eCollection 2021.
In order to investigate the effect of pre-loading damage on the structural performance of Carbon Fiber Reinforced Polymer (CFRP) strengthened Reinforced Concrete (R.C.) beams, experimental and Finite Element Modelling (FEM) investigation was carried out on six R.C. beams. Five of the R.C. beams were damaged up to different levels of strain in the main steel bars before Flexure CFRP strengthening. One of the R.C. beams loaded up to failure and was kept as a control beam for comparison. The experimental results showed that the failure mode of the CFRP strengthened specimen was controlled by CFRP debonding followed by concrete crushing; however, the control beam failed in concrete crushing after yielding the steel bars, which is a ductile failure. The CFRP sheet increases the strength and initial stiffness of the R.C. beams and reduces ductility and toughness. Also, CFRP application increases the first crack and yielding steel bars load by 87.4% and 34.4%, respectively. Furthermore, the pre-damage level does not influence the strength and ductility of the strengthened R.C. beams except for the highest damage levels, which experienced a slight decrease in load capacity and ductility. However, the initial stiffness decreases with increasing pre-damage levels by 40%. Design guideline ACI 440.2R (2004) predicts the ultimate load capacity marvelously for externally bonded Fiber-Reinforced Polymer (FRP) beams compared to the experimental maximum load capacity. The excellent agreement between experimental and FEM results indicates that the constitutive models used for concrete and reinforcement and the cohesive interface model can well capture fracture behavior. However, The FEM analysis predicts the beam to be slightly stiffer and more robust, probably because of the assumed perfect bond between concrete and reinforcement. The developed FEM can be used for further parametric study.
为了研究预加载损伤对碳纤维增强聚合物（CFRP）加固钢筋混凝土（R.C.）梁结构性能的影响，对六根 R.C.梁进行了实验和有限元建模（FEM）研究。五根 R.C.梁在弯曲碳纤维增强聚合物（CFRP）加固前，在主筋中达到不同应变水平的损伤。其中一根 R.C.梁加载至破坏，并作为对比保留为控制梁。实验结果表明，CFRP 加固试件的破坏模式由 CFRP 脱粘控制，随后是混凝土压碎；然而，控制梁在屈服钢筋后混凝土压碎失效，这是一种延性破坏。CFRP 板增加了 R.C.梁的强度和初始刚度，并降低了延性和韧性。此外，CFRP 的应用分别将第一裂缝和屈服钢筋的荷载提高了 87.4%和 34.4%。此外，除了最高损伤水平外，预损伤水平不会影响加固后的 R.C.梁的强度和延性，在最高损伤水平下，其承载能力和延性略有下降。然而，初始刚度随预损伤水平的增加而降低了 40%。设计指南 ACI 440.2R（2004）与实验最大荷载相比，极好地预测了外部粘结纤维增强聚合物（FRP）梁的极限荷载能力。实验和 FEM 结果之间的良好一致性表明，用于混凝土和钢筋的本构模型以及内聚界面模型可以很好地捕捉断裂行为。然而，FEM 分析预测梁的刚度稍大且更坚固，这可能是由于混凝土和钢筋之间假定的完美粘结。开发的 FEM 可用于进一步的参数研究。
