Estimation of the Strain Concentration Factor in Concrete-Coated Steel Pipes Using a Beam Element Finite Element Model

Abstract Concrete coating is used to stabilize subsea steel pipelines against hydrodynamic forces. However, stiffness differences at field joints can cause strain concentration, which may affect the pipeline's integrity. Existing methods to assess strain concentration, including full-scale testing and finite element modeling with solid elements, provide accurate results but are often costly and slow. This study presents a finite element model using beam elements to estimate the strain concentration factor in concrete-coated pipelines under pure bending. The model includes the nonlinear material behavior and the slippage of the concrete coating. The bending moment and resulting strain from the beam model are compared with full-scale tests and solid element models. The comparison shows good agreement and confirms the model's accuracy. The results show that the beam model predicts strain distribution within the range of full-scale tests and solid models while reducing computational effort. The model can be applied to pipelines with different material properties, supporting design and optimization.