Abstract Tubular K-joints, frequently employed in offshore structures, are subjected to multiaxial stresses. It is difficult to accurately assess fatigue strength of tubular K-joints using the uniaxial fatigue theory. In this paper, a multiaxial fatigue life prediction method for tubular K-joints is proposed, which is based on an improved Zero Point Structure Stress (ZPSS) approach that accounts for the stress gradient in the thickness direction to quantify the structure stress at the weld toe of a tubular K-joint. The multiaxial fatigue life is predicted making use of the Modified Wohler Curve Method (MWCM) as the multiaxial damage criterion. It is found that the multiaxial fatigue estimation using the proposed method predicts the fatigue critical point well. Meanwhile, the estimated multiaxial fatigue lives are much closer to experimental lives, in comparison with the uniaxial fatigue estimation using the CIDECT specification.

中文翻译：

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使用替代结构应力方法预测管状 K 型接头的多轴疲劳寿命

摘要 在海上结构中经常使用的管状 K 形接头承受多轴应力。使用单轴疲劳理论很难准确评估管状 K 形接头的疲劳强度。在本文中，提出了一种管状 K 接头的多轴疲劳寿命预测方法，该方法基于改进的零点结构应力 (ZPSS) 方法，该方法考虑了厚度方向的应力梯度，以量化焊缝处的结构应力管状 K 关节的脚趾。使用修正的沃勒曲线法 (MWCM) 作为多轴损伤准则来预测多轴疲劳寿命。发现使用该方法的多轴疲劳估计能很好地预测疲劳临界点。同时，估计的多轴疲劳寿命更接近于实验寿命，