基于非线性海床刚度模型的钢悬链线立管动力响应分析

Dynamic response analysis of steel catenary riser based on a nonlinear seabed stiffness model

基于P-y曲线模拟钢悬链线立管(SCR)-海床相互作用的力学行为,运用弹性地基梁模拟SCR流线段,研究海床刚度模型对SCR动力响应的影响。立管与海床的相互作用取决于土刚度、立管特性和沟槽的发展等诸多因素。现在的方法大多是将海床模拟为线性或非线性弹簧系统,而没有考虑土的塑性变形和吸力效应。运用P-y曲线模拟管-土相互作用过程,内容包括:①在浮体升沉运动和波浪载荷作用下,得到了管-土作用的荷载位移曲线、贯入深度和海床分布力的变化情况;②分析立管触地点的位移、弯矩、应力等动力响应特征,与线弹性海床模型进行了比较。研究表明,非线性海床土刚度模型较为准确地模拟了土的塑性变形和约束力对立管触地区动力响应的影响,弹性地基梁单元较好地模拟了立管的流线段,荷载位移曲线也体现了土吸力的产生和释放过程。

Here,the interaction behavior between SCR and seabed was simulated based on the P-y curve,the influence of a nonlinear seabed stiffness model on the dynamic response of SCR was studied using an elastic foundation beam to simulate SCR flow line.It was shown that the riser-seabed interaction depends on several factors,such as,soil stiffness,riser characteristics,and development of trenches.In the current most methods,the seabed was taken as a linear or nonlinear spring system not considering plastic deformation of soil and its suction effect.The P -y curve was used to simulate the relation between seabed resistance force and the vertical penetration of the riser into seabed during their interaction.The interaction between SCR and soil＇s hysteretic load-penetration curve,the depth of penetration and the envelop curve of seabed contributed force under cyclic heave motion and linear wave were obtained.Time histories of the contact points between SCR and soil＇s vertical displacement,bending moment,effective tension and stresses were analyzed.The results using the nonlinear seabed model were compared with those using the linear seabed model.The results showed that the nonlinear seabed stiffness model has a significant influence on the dynamic responses of SCR;the elastic foundation beam element simulates the SCR＇s flow line better,and the load-penetration curve reveals the genearation and release of suction.