Investigation of fatigue properties of girth welds with root imperfections allowed by API 1104. Final report
- Edison Welding Institute, Columbus, OH (United States)
The work described in this report was aimed at determining the effect of root imperfections allowed by API 1104 on the fatigue properties of girth welds, and to recommend a S-N curve appropriate for girth welds in pipelines. To accomplish this objective, S-N curves were developed for single-sided girth welds without a backing strip using pipe strip specimens containing the various sizes of incomplete root penetration and lack-of-root sidewall fusion; these imperfections are currently allowed by API 1104. The different root imperfection sizes investigated in this project were 1/16- x 0.5-in. (1.6 x 12.7 mm), 1/16- x 1.0-in. (1.6 x 25.4 mm), and 1/8- x 1.0-in. (3.2 x 25.4 mm). Baseline fatigue data for nominally sound weld joints were also developed. The results from the baseline weld pipe strip specimens were compared to the full pipe section results available from the literature. It was concluded that the results from the baseline pipe strip specimens adequately represent the fatigue performance of full pipe sections loaded axially or in bending. Therefore, a baseline weld design curve was developed using both pipe strip specimens and full pipe section data. All test results for axial or bending loads lie above the proposed fatigue design curve. The lack of definitive data on pipes subjected to fluctuating internal pressure confounds attempts to extend the applicability of the proposed fatigue design curve to this important loading condition. The influence of root imperfection size on the fatigue performance was also assessed. Again, the lack of definitive data for full pipe sections confounds attempts to extend the applicability of the proposed fatigue curves to this loading condition. In summary, S-N design curves are proposed for nominally sound girth welds and for girth welds containing various sizes of root imperfections that are loaded axially or in bending. 18 refs., 31 figs., 16 tabs.
- Research Organization:
- American Gas Association, Inc., Arlington, VA (United States). Pipeline Research Committee
- Sponsoring Organization:
- American Gas Association, Inc., Arlington, VA (United States)
- OSTI ID:
- 576020
- Report Number(s):
- AGA-98002868; EWI-07279CAP; CNN: Contract PR-185-9432; TRN: 98:001472
- Resource Relation:
- Other Information: PBD: 9 Jan 1997
- Country of Publication:
- United States
- Language:
- English
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