# Response of Corroded Steel Pipeline Without and with CFRP Reinforcement to Reverse Fault Movement
## 5 Conclusions  
It is necessary to reinforce the cross-fault pipeline with corrosion defects. In this study, a 3D finite element model of a pipeline with corrosion is developed to analyze the impact of corrosion on the response and failure mode of the pipeline crossing a reverse fault. The effectiveness of CFRP reinforcement and its thickness and length are further evaluated to investigate the positive effect on corroded pipelines. The following conclusions are drawn:  
(1) Corrosion defect amplifies the axial strain response and weakens the seismic performance of the pipeline crossing a reverse fault. The strain of the pipeline in the corroded area increases linearly with corrosion extent, at about 0.01 increase for every 10% reduction in thickness. Corrosion at different positions of the pipeline will significantly amplify the mechanical response and promote the pipeline's failure process.  
(2) Corrosion defect promotes the transition of cross-fault pipeline from a single failure mode to multiple failure modes, increasing the risk of pipeline failure. When the fault displacement exceeds 0.8 m, the pipeline with corrosion at the hanging wall already experienced failure of local bulking and tensile fracture compared with the intact pipeline only experiencing local bulking.  
Figure 16: Cross-section deformation of the pipeline before and after CFRP reinforcement.  
Figure 15: The stress diagram of the corroded pipeline before and after CFRP reinforcement.  
(3) CFRP reinforcement can alleviate strain concentration, eliminate local buckling, and improve irregular deformation of the pipeline crossing a reverse fault. The compressive resistance of the corroded pipeline is moderately enhanced by the CFRP reinforcement. The section deformation at the reinforced position is like that of a non-corroded pipeline. In addition, it is found that the increase in thickness and length of CFRP reinforcement can enhance the pipeline buckling resistance, but at a decreasing rate, as the reinforced thickness/length increases. Considering the economy of the actual project, combined with the relevant calculation results in this study, it is suggested to wrap 4 layers of CFRP with a length of 5 m on the pipeline wall at the corrosion location to obtain the most cost-efficient reinforcement effect.  
Conceptualization, J.H.; methodology, B.H.; software, Y.B. and W.Z.; validation, Y.B., W.Z. and M.H.E.N.; formal analysis, Y.B. and W.Z.; investigation, J.H.; resources, J.H. and B.H.; data curation, J.H. and Y.B.; writing--original draft preparation, J.H.; writing--review and editing, M.H.E.N.; visualization, Y.B. and W.Z.; supervision, B.H. and M.H.E.N.; project administration, J.H. and B.H.; funding acquisition, J.H. and B.H. All authors have read and agreed to the published version of the manuscript.  
This research is funded by the National Key Research and Development Program of China (2023 YFC3007404) and the National Natural Science Foundation of China (No. 52478487).  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors upon request.  
The authors declare no conflicts of interest.