Structural Performance and Design Implications of Cured-in-Place-Pipe liners Under Radial Compression

Understanding the structural behavior of cured-in-place pipe (CIPP) liners under radial compression is essential for ensuring the long-term reliability of trenchless rehabilitation systems. This study presents a comprehensive experimental and numerical investigation of CIPP liners under radial compression, aiming to elucidate their material behavior, structural response, and design implications. Three-point bending and tensile tests were conducted to characterize the mechanical properties and failure mechanisms of the liner material, consisting of three layers of fiberglass cloth. Full-scale radial compression tests examined the influence of loading speed, liner diameter, thickness, and loading times on ring stiffness and bearing capacity, revealing a progressive deformation process through initial, elliptical, and dumbbell stages, with failure governed primarily by geometric instability. To account for cumulative cyclic effects, a loading times correction factor was incorporated into a Spangler-based bearing capacity calculation, enabling quantitative evaluation of stiffness degradation and strength reduction under repeated loading. Sensitivity analysis indicated that liner thickness has the greatest influence on structural performance, followed by diameter, loading times, and loading speed. A three-dimensional finite element model was developed and validated against experimental data, accurately reproducing load–deformation behavior and stress evolution. The proposed calculation method and numerical model provide a reliable framework for optimizing liner design, predicting long-term performance, and supporting engineering safety assessment of CIPP rehabilitation systems.