Session: SE-07-01 Seismic Evaluation of Systems, Structures and Components

Paper Number: 105706

105706 - Simplified Method for Seismic Assessment of Buried Pipeline With Local Wall Thinning 

Local wall thinning due to corrosion must be considered to ensure the long-term structural integrity of a buried pipeline. In seismically-active areas, buried pipelines are especially subjected to cyclic deformation behavior due to seismic motion.  Therefore, an assessment procedure to evaluate the integrity of buried pipelines with local corrosion against the seismic motion is needed. This paper proposes a simplified method for seismic assessment of buried pipelines with local wall thinning. First, assuming that the buried pipeline is subjected to seismic motion, cyclic axial loading tests using a steel pipe with an artificial local wall thinning and finite element analysis (FEA) were conducted to clarify the deformation behavior and fracture behavior. Elephant foot buckling and low cycle fatigue modes were respectively observed, depending on the dimension of local wall thinning. In the elephant foot buckling mode, first, the thinned area buckled locally with bulging deformation under compressive loading. Then, the bulging deformation increased according to the cyclic loading leading to the elephant foot buckling. In the low cycle fatigue mode, the thinned area buckled locally with dent deformation under compressive loading; subsequently, the dent deformation repeated with cyclic loadings. Finally, low cycle fatigue cracks propagated at the thinned area. The test pipes resulted in failure after several cycles. Based on local buckling behavior at the thinned area during the first cycle compressive loading, a simplified method for the design code based seismic assessment of buried pipelines with local wall thinning was proposed. The proposed method can evaluate the seismic performance of the pipe with local wall thinning by simple equations using the axial seismic load, cross-section dimension and material strength of the steel pipe, and dimension of the local wall thinning area as the input values. Finally, the proposed method was verified by comparing the results with the seismic assessment results using FEA for various combined conditions of the pipe specifications and wall thinning dimension.

Presenting Author: Shoma Onuki Tokyo Gas

Presenting Author Biography: Shoma Onuki was born in Saitama, Japan. He entered the University of Tohoku, Japan in the spring of 2004. He majored in mechanical engineering and received his Bachelor of Engineering Degree in 2013 and Master of Engineering Degree in 2015. After graduation, he went to work for Tokyo Gas Co., Ltd., in Tokyo as a research engineer. Since then, he has engaged in structural integrity assessment of gas supply equipments such as gas pipeline at the research institute in Tokyo Gas. The area of his specialty is elastic-plastic deformation and fracture behavior of steel structures.

Authors:

Shoma Onuki Tokyo Gas
Masaki Mitsuya Tokyo Gas co.,ltd.