| dc.description.abstract | Long-term mechanical properties are critical parameters for the design and performance of thermoset Cured-in-Place Pipe (CIPP) gravity and pressure liners. These liners have been used extensively across North America; however, their long-term performance has not been extensively studied. The purpose of this research is to better understand CIPP liners by experimentally quantifying the mechanical response of the liner under flexure, tension, and internal pressure loading conditions. Non-reinforced and reinforced CIPP long-term (50-year) flexural modulus, tensile modulus, and flexural strength were estimated, and the Creep Retention Factors (CRF) and Strength Retention Factors (SRF) to be applied to the short-term flexural and tensile mechanical properties, were determined. It also provides CIPP short-term hydrostatic burst response for a 150-mm and 200-mm I-Main composite pressure CIPP liner. It estimates the Pressure Rating (PR) using the well-established Hydrostatic Design Basis (HDB) design approach. For flat plate testing, 10,000-hour flexural and tensile creep tests were conducted on I-Main test coupons under a stress level that is 25% of the liner yield strength, and 3,000-hour plus flexural creep-rupture tests were performed completed on various non-reinforced and reinforced CIPP flat coupon specimens. A customized burst facility was designed, constructed, and commissioned for full-scale pipe testing to obtain unique CIPP HDB test data to develop a CIPP HDB regression line.
Results show that the long-term (50-year) flexural CRF does not correspond with the tensile CRF values. Also, the long-term (50-year) flexural SRF for both non-reinforced and reinforced test specimens were compared and found not to agree with the generalized SRF (50%) typically used for design. For the case of full-scale pipe testing, results found that the CIPP liner specimens, having no known physical defect, demonstrated significant variability, which was experimentally inferred to be due to the presence of invisible liner imperfections such as microscopic air voids. A regression analysis of CIPP HDB data found that the CIPP design factor, based on the ratio of the short-term burst strength to the 50-year Long-term Hydrostatic Strength (LTHS), agrees with previous research on thermoplastics and glass-reinforced pipes. The most important finding is that, for the particular pressure CIPP specimens used in this research, the 50-year LTHS and HDS, found by extrapolation of the experimental data, were comparable to similar thermoset and thermoplastic pressure pipes that use the HDB method. This finding implies that the HDB design approach has a high potential to advance CIPP testing and design to standardize all watermain CIPP products. | en |
