Seismic Assessment Formula for a Buried Pipeline With Local Wall Thinning

Abstract

The structural strength of buried pipeline may be reduced by local wall thinning owing to corrosion in long-term operations. In seismic active area, it is necessary to ensure the integrity of buried pipeline with wall thinning against seismic motion. This study proposed a seismic assessment formula for a pipe with wall thinning subjected to cyclic axial loading assuming seismic motion. Cyclic axial loading experiments using pipes with wall thinning and finite element analysis (FEA) were conducted to study the failure behavior. The pipe with wall thinning deformed starting from the wall-thinning part, and finally plastic collapse due to elephant foot buckling or leakage at the wall thinning due to low-cycle fatigue occurred in several to ten and several cycles. Based on the deformation mechanism at wall thinning, a seismic assessment formula was proposed. The proposed formula can easily evaluate the seismic performance of the pipe with wall thinning against design seismic motion. The formula was validated by the results of experiments and FEA. In addition, based on the proposed formula, the assessment curves for an allowable wall-thinning size against design seismic motion were illustrated. The formula can be used to formulate standards and assess the safety of pipes with wall thinning that are subjected to seismic motion.