Static and fatigue behaviour of internal replacement pipe systems subjected to surface load from vehicular traffic

Static and fatigue behaviour of internal replacement pipe systems subjected to surface load from vehicular traffic

Internal replacement pipe (IRP) systems are a new and emerging trenchless technology utilised for rehabilitating legacy gas and oil pipes with circumferential cracks or discontinuities. IRP systems necessitate a design and development approach that ensures their reliable performance and durability against various types of loads throughout their service life. This thesis systematically investigated the static and fatigue behaviour of IRP systems in discontinuous host pipes under vehicular traffic loading to ensure their effective design and implementation. The first investigation involved the numerical analysis of the static bending behaviour of legacy pipes repaired with IRP systems, specifically focusing on those with full circumferential cracks or discontinuities. The influence of critical design parameters, such as width of host pipe discontinuity, thickness and elastic modulus of IRP, on the bending behaviour of pipe repair systems was investigated. A simplified and robust analytical model that can effectively capture the nonlinear lateral deformation behaviour of different IRP systems, including stand-alone IRP, IRP installed within a continuous host pipe and IRP installed within host pipes with discontinuities was also developed. In the second study, the flexural fatigue performance of IRP systems completely bonded to discontinuous host pipe segments was analysed numerically under repeated traffic loading. A comprehensive parametric study was conducted to assess the impact of important design parameters, including discontinuity width, thickness and elastic modulus of IRP, and the magnitude of the traffic loading, on the bending fatigue performance. The combined effect of the internal pressure and traffic load on the flexural fatigue behaviour of IRP systems installed in discontinuous legacy pipes was examined numerically in the third study. The last investigation was undertaken to numerically investigate the influence of bonding level on the flexural fatigue performance of IRP systems. The findings of this research provided a better understanding of the static and fatigue behaviour of IRP systems and the effect of critical design parameters on their lateral deformation behaviour and fatigue life. The numerical results, simplified analytical models, mathematical equations and design charts developed from this study will provide valuable insight for pipeline developers and designers, enabling them to enhance the safety, reliability, and cost efficiency of IRP systems.

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