Seismic Performance Assessment of Cured-in-Place-Pipe Lined Cast Iron Pipes

Cured-in-place pipe (CIPP) liners are increasingly used to rehabilitate aging cast-iron (CI) water mains, yet their seismic performance remains insufficiently understood. CI pipelines, which form much of the legacy water infrastructure, have historically suffered joint failures during earthquakes, underscoring the need for reliable fragility models for proactively managing them. The need for reliable fragility models is paramount when considering their rehabilitation using lining methods such as CIPP. This study examines the seismic fragility of CI pipelines before and after CIPP rehabilitation by performing finite-element (FE) analysis. A 3-km two-dimensional FE model was initially constructed and validated against experimental and numerical benchmarks. Incremental dynamic analysis was then performed using 12 near-field seismic records scaled to a range of peak ground strain (PGS) values, and three ASCE 7 soil classes (D, C, and B) were considered to capture the influence of varying soil stiffness. Fragility curves were then developed to relate repair rate per kilometer to PGS. Results show that CIPP rehabilitation significantly mitigates joint failures at moderate-to-high ground strains, and the findings are compared with existing fragility relations. This study is a valuable resource for municipalities and decision-makers seeking informed approaches to enhance the seismic performance of buried pipes.