Abstract Due to the spatial complexity and fabrication characteristics of offshore platforms, it is inevitable to encounter overlaps or proximity of weld lines in tubular joints. Several international standards such as American Petroleum Institute (API), American Welding Society (AWS), and American Institute of Steel Construction (AISC) regulate the minimum distance between primary weld beads; however, any logical and detailed background of this limitation has not been presented. For a non-compliant weld joint where the regulation is not met, fracture toughness calculation is a typical index to verify the structural integrity. This research consists of two parts. First, weld residual stress distributions are calculated by a 3D thermo-mechanical nonlinear Finite Element Analysis. Two crossing welds, a T-weld crossing on a butt weld, are simulated in one model. A separate tee and a butt welding simulations are also performed for a comparative purpose. Second, SIFs and J-integral values are calculated at the surface and deepest crack tip locations for four different types of semi-elliptical surface cracks. Four cracks are embedded into the weld model and the residual stress distribution from the 3D thermo-mechanical FEA are mapped to a 3D FE crack model as initial conditions. An additional axial tensile load is also imposed. SIF values are compared with those using the weighting function method for the butt weld model subject to three load cases, i.e., tensile stress only, weld residual stress only, and both of them. From the simulation, a tubular joint containing a chord girth weld intersected with weld beads of brace is found to show lower the SIF values than that having only a girth weld on chord.

中文翻译：

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焊接残余应力对海上管状结构两条焊缝相交处断裂韧性的影响

摘要 由于海上平台的空间复杂性和制造特点，在管接头中不可避免地会遇到焊接线的重叠或接近。美国石油学会（API）、美国焊接学会（AWS）、美国钢结构学会（AISC）等多项国际标准规定了初级焊道之间的最小距离；但是，没有介绍这种限制的任何合乎逻辑的和详细的背景。对于不符合规定的不合规焊接接头，断裂韧性计算是验证结构完整性的典型指标。本研究由两部分组成。首先，通过 3D 热机械非线性有限元分析计算焊接残余应力分布。两个交叉焊缝，在对接焊缝上交叉的 T 形焊缝，在一个模型中进行模拟。出于比较目的，还进行了单独的三通和对焊模拟。其次，计算了四种不同类型的半椭圆形表面裂纹的表面和最深裂纹尖端位置的 SIF 和 J 积分值。焊接模型中嵌入了四个裂纹，并将 3D 热机械 FEA 的残余应力分布映射到 3D FE 裂纹模型作为初始条件。还施加了额外的轴向拉伸载荷。SIF 值与使用加权函数法的对接焊缝模型在三种载荷情况下进行比较，即只有拉应力，只有焊缝残余应力，以及这两种情况。从模拟来看，