为研究双层螺旋曲杆束在拉-弯耦合作用下的力学行为及其内部钢丝协同工作机理，考虑丝间摩擦滑移，建立了层间接触、同步接触两类典型条件下的侧丝微段静力平衡关系并进行了解析推导，同步提出一种改进的半精细化有限元模型进行数值模拟和结果对比。由弯曲变形时侧丝所受剪切力的分布规律获得了两类接触条件下的丝间相对滑移方向，并在此基础上根据平衡方程推导得到侧丝滑移后的轴力限值；通过对各丝贡献的弯矩求和得到在拉-弯耦合作用下曲杆束各截面的弯矩-局部曲率关系式，并提出一种简化的弯矩-曲率均值关系式描述其整体弯曲行为。结果表明：由于侧丝沿曲杆束整体轴向周期旋转，相邻丝之间接触面有滑移驻点，且驻点两侧相对滑移方向相反；侧丝-侧丝、侧丝-芯丝接触面的滑移驻点、初始滑移位置不同；忽略内部滑移扩展过程，两类接触条件下双层螺旋曲杆束具有相同的弯矩-曲率均值关系式，函数图像呈双折线；半精细化有限元模型滑移前后的弯曲变形结果与解析值的相对误差小于4%，且提取的丝间相对滑移结果规律与分析结论相符。

To study the mechanical behavior of 2-layer spiral strand under tension-bending coupling effect and the cooperative working mechanism of internal wires, inter-wire friction and slip were taken into consideration. Static equilibrium relationships for micro-segments of layer-wire were established and analytically derived under two typical contact conditions: inter-layer contact and coupled contact. At the same time, an improved semi-refined finite element model was proposed for numerical simulation and result comparison. Relative slip direction between wires on two contact conditions were obtained from the distribution of shear force on layer-wire, based on which the axial force limit of layer-wire after sliding was derived according to the equilibrium equation. The bending moment-local curvature relation of spiral strand was obtained by summing the bending moments contributed by each wire under tension-bending coupling effect, and a simplified bending moment-mean curvature relation was proposed to describe bending behavior of the spiral strand. The result shows that there are slip stagnation points on contact surface of adjacent wires because layer-wire rotates along the axis of spiral strand periodically, and relative slip direction on both sides of the stagnation point is opposite. The slip stagnation point and initial slip position on contact surface of layer-wire to layer-wire and layer-wire to core-wire are different. When neglecting the progression of internal slip, 2-layer spiral strand exhibits the same bending moment-mean curvature relationship under both contact conditions, and the function graph presents a bilinear form. The relative error of the bending deformation results before and after slipping between semi-refined FE model and analytical values is less than 4%, and the extracted relative slip results are in agreement with the analysis conclusions.