Composite versus Stand-Alone Design Methodologies for Carbon Fiber Lining Systems

Fiber Reinforced Polymer (FRP) composite lining systems are used by major municipalities throughout the United States to structurally rehabilitate and upgrade large diameter pipelines. For internal Carbon Fiber Reinforced Polymer (CFRP) lining systems addressing prestressed concrete cylinder pipes (PCCP), there are two design approaches utilized relative to interaction with the host pipe structure. These approaches are referred to as stand-alone and composite. For a stand-alone design, the carbon fiber takes 100% of the loads acting on the pipeline system with no reliance on the host pipe for structural integrity. Composite designs rely on the carbon fiber lining system and inner concrete core of the PCCP to interactively provide a structural system to resist the loads. A composite design approach relies on the inner core to resist bending and buckling due to external loads such as soil cover, water table, vehicular loads and vacuum pressure. When applicable, this type of design can be more cost-effective because the amount of carbon fiber materials utilized can be less than stand-alone design. This paper presents design limit states and includes information from recent research, development, and testing. It discusses factors to be considered, potential challenges and best practices for determining stand-alone versus composite designs for carbon fiber lining systems.

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