THE EFFECTIVE NOTCH STRESS APPROACH FOR FATIGUE ASSESSMENT OF WELDED TUBULAR JOINTS

Abstract

The effective notch stress (ENS) approach has gained increasing industrial acceptance since it provides a uniform basis for the fatigue assessment of welded joints through its single and universal S-N curve. This thesis investigates two key aspects of the ENS concept application on welded tubular joints: 1) the validity of the existing S-N curve for as-welded tubular joints, and 2) the possible simplifications for the ENS computation in tubular joints. The first part of this thesis presents a systematic assessment of the existing S-N curve against published tubular joint fatigue tests. This study contributes substantial experimental evidence confirming the suitability of the existing S-N curve for tubular joints, which was derived originally from non-tubular joint tests. The remaining parts of this thesis address the high computational effort required in the ENS calculation. This thesis proposes two experimentally-validated simplifications that allow for accurate ENS estimations on tubular X- and K-joints. Both simplified procedures demonstrate compatibility with the existing S-N curve.