Abstract Bolted connections are widely used in steel structures such as steel buildings, bridges, transmission line steel towers, in which the stress behavior of the bolt is very complex, including tension, shear and bending moment. The load-transferring mechanism along engaged threads is difficult to grasp, especially under the alternating loads or dynamic loads. Therefore, a three-dimensional finite element model with helical threads being considered is established, whose accuracy is validated through the corresponding test. Then, the load-transferring behavior along the engaged threads under axial tension, such as the stress distributions, axial load distributions along the thread, are all investigated. Finally, a modified equation that refers to the elastic thread mechanics proposed by Yamamoto is proposed based on the numerical results, and the impact factor R defined as the ratio of actual force to average axial tension is adopted for the evaluation of load distributions along bolt threads. The results show that during the whole loading process, the load-sharing proportions of 1st and 2nd bolt threads increase first and then decrease, and that of the 3rd thread has no obvious change, and those of other threads decrease first then increase linearly. The slippages in engaged threads zone 0.22P apart from the nut loaded surface do not occur, and the slippages of the zone from 0.22P to 0.61P rapidly increase and get to maximum, after that decrease linearly. Besides, the modified formula, which takes the effects of the plastic deformation and contact surfaces into account, is proved to be more reasonable.

中文翻译：

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轴向拉力下高强螺栓啮合螺纹传力机理及计算理论

摘要 螺栓连接广泛应用于钢结构建筑、桥梁、输电线路钢塔等钢结构中，其中螺栓的受力行为非常复杂，包括拉、剪和弯矩。沿啮合螺纹的载荷传递机制难以掌握，尤其是在交变载荷或动态载荷下。因此，建立了考虑螺旋螺纹的三维有限元模型，并通过相应的试验验证了其精度。然后，研究了在轴向张力下沿啮合螺纹的载荷传递行为，例如应力分布、沿螺纹的轴向载荷分布。最后，基于数值结果提出了参考 Yamamoto 提出的弹性线力学的修正方程，影响因子 R 定义为实际力与平均轴向拉力的比值，用于评估沿螺栓螺纹的载荷分布。结果表明，在整个加载过程中，第1、第2螺栓螺纹的载荷分担比例先增加后减小，第3螺纹无明显变化，其他螺纹则呈先减小后线性增加的趋势。与螺母加载面相距0.22P 的啮合螺纹区域的滑移不发生，并且从0.22P 到0.61P 区域的滑移迅速增加并达到最大值，然后线性减小。此外，考虑到塑性变形和接触面影响的修正公式被证明更合理。