RR90 - Re-evaluation of fatigue curves for flush-ground girth welds

The fatigue performance of girth welded steel pipes with the weld cap and root flush ground is designated as class C in the British standard BS 7608 code for fatigue design. However, this is not based on experimental data. Since fatigue results for flush-ground girth welds in steel pipes have now become available, it is necessary to re-evaluate the design of the S-N curve(s), for such welds on the basis of the relevant experimental data. For flush-ground joints, internal defects become the weak link in the fatigue performance. The effect of embedded flaws on fatigue design must also be therefore re-assessed since the current embedded flaw acceptance criteria were also based on joints in flat plate rather than girth welds. A comprehensive examination of published works regarding fatigue performance of flush ground welds with and without reportable flaws was carried out. Discussion and communications were also held with research workers in this area. Reports a number of conclusions, including the setting up of a database of fatigue test results for flush ground girth welds that has been statistically analysed.

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Updated 2021-04-15