Simplified Method for Seismic Assessment of Buried Pipeline With Local Wall Thinning

Abstract

Abstract This study proposed a seismic assessment formula for pipes with wall thinning subjected to cyclic axial loading assuming seismic motion. Cyclic loading experiments using pipes with wall thinning were conducted to study the deformation and failure behavior. Two deformation modes were observed: buckling and bending deformations at the point of wall thinning. In the buckling mode, the buckling deformation at wall thinning progressed in accordance with the number of cyclic loading; finally, plastic instability occurred due to elephant foot buckling at full pipe cross-section. In the bending mode, the bending deformation at wall thinning was repeated by cyclic loading. Subsequently, fatigue cracking initiated and penetrated the remaining pipe thickness at wall thinning. Based on the deformation behaviors at wall thinning during cyclic loading, simplified seismic assessment formula was proposed. The proposed formula can easily evaluate the seismic performance of the pipe with wall thinning against seismic motion. The formula was validated using finite element analysis for different wall thinning sizes and pipe properties. In addition, based on the proposed formula, the assessment curves were plotted for allowable size of the wall thinning against seismic motion. The formula can be used to formulate standards and assess the safety of pipes with wall thinning that are subjected to seismic motion.