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Research Papers

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane, and Mixed Mode Bending Under Seismic Load: An Experimental Approach

[+] Author and Article Information
Izumi Nakamura

Hyogo Earthquake Engineering Research Center, National Research Institute for Earth Science and Disaster Prevention, Japan, 3-1, Tennnodai, Tsukuba-shi, Ibaraki 305-0006, Japanizumi@bosai.go.jp

Akihito Otani

Nuclear Power Division, IHI Corporation, 1, Shin-Nakahara-cho, Isogo-ku, Yokohama 235-8501, Japanakihito_ootani@ihi.co.jp

Masaki Shiratori

Center for Risk Management and Safety Sciences, Yokohama National University, 79-5, Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japanmasaki@swan.me.ynu.ac.jp

J. Pressure Vessel Technol 132(3), 031001 (Apr 28, 2010) (8 pages) doi:10.1115/1.4001517 History: Received December 25, 2007; Revised May 27, 2009; Published April 28, 2010; Online April 28, 2010

Pressurized piping systems used for an extended period may develop degradations such as wall thinning or cracks due to aging. It is important to estimate the effects of degradation on the dynamic behavior and to ascertain the failure modes and remaining strength of the piping systems with degradation through experiments and analyses to ensure the seismic safety of degraded piping systems under destructive seismic events. In order to investigate the influence of degradation on the dynamic behavior and failure modes of piping systems with local wall thinning, shake table tests using 3D piping system models were conducted. About 50% full circumferential wall thinning at elbows was considered in the test. Three types of models were used in the shake table tests. The difference of the models was the applied bending direction to the thinned-wall elbow. The bending direction considered in the tests was either of the in-plane bending, out-of-plane bending, or mixed bending of the in-plane and out-of-plane. These models were excited under the same input acceleration until failure occurred. Through these tests, the vibration characteristic and failure modes of the piping models with wall thinning under seismic load were obtained. The test results showed that the out-of-plane bending is not significant for a sound elbow, but should be considered for a thinned-wall elbow, because the life of the piping models with wall thinning subjected to out-of-plane bending may reduce significantly.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic illustration of the three types of bending direction on an elbow: (a) in-plane bending, (b) out-of-plane bending, and (c) mixed bending

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Figure 2

Configuration of models for the piping system test: (a) MODEL_0 (in-plane bending), (b) MODEL_1 (out-of-plane bending), and (c) MODEL_2 (in-plane and out-of-plane bending)

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Figure 3

Configuration of wall thinning at an elbow

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Figure 4

Narrow band random wave used for the piping system test: (a) time history of input acceleration and (b) response spectrum (h: damping ratio)

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Figure 5

Strain and outer diameter measurement sections around Elbow 1 and Elbow 2: (a) strain measurement section around Elbow 1 and Elbow 2, (b) diameter measurement section of Elbow 1 and Elbow 2 (for MODEL-0, measured at section A only), and (c) strain and diameter measured points in cross section

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Figure 6

Applied moments around Elbow 1 and Elbow 2: (a) 3D_A01, (b) 3D_A11, and (c) 3D_A21

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Figure 7

Relation between input acceleration and response acceleration at Elbow 3

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Figure 8

Relation between input acceleration and response displacement at Elbow 3

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Figure 9

Diameter deformation ratios of Elbow 1 and Elbow 2 for all test models: (a) MODEL_0, and (b) MODEL_1 and MODEL_2

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Figure 10

Diameter deformation ratios of Elbow 1 for 3D_C12 and 3D_C22: (a) 3D_C12 and (b) 3D_C22

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Figure 11

Failure modes obtained by the shake table tests: (a) 3D_C01, Elbow 1; (b) 3D_C21, Elbow 1; and (c) 3D_C22, Elbow 1

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