Mechanical behavior of ductile iron pipe push-on joints rehabilitated with CIPP liner subjected to bending moment

The cured in place pipe (CIPP) technology is widely applied for rehabilitation of water supply pipelines. For ductile iron (DI) pipelines—critical components of water transmission infrastructure—understanding the mechanical behavior of push-on joints after liner reinforcement is essential. This study establishes a three-dimensional nonlinear finite element model of CIPP-reinforced DI pipes with push-on joints, validated through experimental tests. Key findings reveal: Increasing the liner elastic modulus from 30 to 60 GPa enhances initial stiffness by 36% but intensifies stress concentration at contact regions by 65%. A 3 mm increase in liner thickness elevates yield load by 98%, yet excessive thickness induces localized stress peaks due to stiffness concentration, necessitating balanced structural rigidity and stress homogeneity. Elevated internal pressure reduces liner yield load, suppresses bending deformation, and diminishes flexural bearing capacity by approximately 8.2% while decreasing tensile stress at the invert.