中文摘要：

以一类八层非粘结柔性立管为研究对象，对防摩擦层分别采用计人实际几何形状的螺旋带模型和简化的圆柱壳模型，采用理论和数值方法计算立管在不同边界下的轴向及扭转刚度．计算结果表明：数值解与理论值符合较好；在轴向拉力、逆时针扭矩、顺时针扭矩（限制立管轴向位移）下，使用两种防摩擦层模型对立管刚度影响可以忽略；在轴向压力、顺时针扭矩（自由边界）下，采用圆柱壳模拟防摩擦层会大幅增大立管刚度．

英文摘要：

Two models are chosen to simulate anti-friction layer of an eight-layer unbonded flexible riser, one is the helix model which takes actual geometry into consideration, and the other is the sim- plified cylindrical shell model. Axial and torsional stiffnesses of the unbonded flexible riser under dif- ferent boundary conditions were predicted by analytical and numerical methods. It is shown that nu- merical results agree well with theoretical results. Under axial tension, anticlockwise torsion and clockwise torsion （prevented from moving axially）, stiffnesses obtained by the two models of anti- friction layer are basically the same. Under axial compression and clockwise torsion （free boundary condition）, the cylindrical shell model of anti-friction layer will dramatically increase stiffnesses of the riser.