Developing a Performance Curve for Bar-Wrapped Concrete Cylinder Pipe Based on Residual Factor of Safety Methodology

Bar-wrapped concrete cylinder pipe (BWCCP) is a semi-rigid pressure pipe designed as a composite structure combining the tensile strength of steel with the compressive strength and corrosion-inhibiting properties of Portland cement mortar. As with any infrastructure component, BWCCP water mains are prone to deterioration due to aging and other influencing factors. Hence, developing a performance curve is a must to ensure proactive asset management is implemented. Although the prestressed concrete cylinder pipe (PCCP) and BWCCP both belong to the buried concrete pipes category, unlike PCCP, the steel cylinder and the reinforcement bars in the BWCCP composite undergo identical strains governed by common elastic modulus. Once the steel cylinder yields and reaches its ultimate plastic region, the pipe will fail. Therefore, correlating the adopted structural limit states for PCCP in AWWA C304 (serviceability, yield, and strength limit states) to the BWCCP performance under tension conditions may not adequately represent the pipe’s mechanical behavior. Instead, the BWCCP performance curve will adopt the residual factor of safety approach initially to estimate the BWCCP composite behavior under tension conditions. As this paper provides a methodology to assess BWCCP’s distress status in terms of residual factor of safety, pipes with low factor of safety can be identified, and decision-makers are able to allocate municipal renewal budgets to avoid catastrophic failure of BWCCP assets.