Abstract The global pipeline configuration in installation is mainly governed by static lay effects, which, besides pipeline material properties and geometry, primarily depend on its submerged gravity and horizontal tension provided by the laying vessel. These loads are insensitive to the pipeline deformation and preserve both their values and their directions as the pipeline deforms throughout the whole course of the installation. However, these static lay effects may be significantly amplified by the environmental factors, primarily caused by astronomical ocean tides, such as water level variations and hydrodynamic currents. These factors may substantially affect pipeline configuration and significantly increase the internal forces. Moreover, the loads caused by the ocean currents are of a fundamentally different nature comparing to the gravity and the lay tension. They are nonuniformly distributed along the pipeline axis and change both their values and their directions following the nonlinear deformation of the pipeline throughout the course of the laying process. This paper presents a feasible numerical method for a structural analysis of a pipeline static configuration in installation, subjected to non-uniformly distributed, position- and orientation-dependent loading and water level variations. The method considers the whole pipeline, which is partially suspended and partially laid-on a seabed, as a single continuous segment, and is valid for both S-lay and J-lay techniques. The numerical solution adopts finite difference discretization of the pipeline, and proceeds sequentially in an incremental way, following the actual pipe-lay process. At each length increment a new consequent equilibrium configuration is being assessed by consistent minimization of the updated total potential energy, which allows for considering follower loads, which change both their values and their directions following the nonlinear deformation of the pipeline. Representative parametric study is conducted to demonstrate the feasibility of the method. Considered the effects of a power-law current velocity depth-varying profile and water level variations. The method compared to Abaqus/AQUA and its convergence is validated through finite difference grid refinement. The proposed technique presents a less time-consuming alternative to the available special-purpose commercial software that imposes the use of cumbersome Graphical User Interface for a model definition and a result processing.

中文翻译：

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环境引起的非均匀分布随动载荷作用下海上铺管的数值分析

摘要 管道在安装过程中的整体配置主要受静态铺设效应控制，除管道材料特性和几何形状外，静态铺设效应主要取决于铺设船提供的水下重力和水平张力。这些载荷对管道变形不敏感，并且在管道在整个安装过程中变形时保持它们的值和方向。然而，这些静态影响可能会被环境因素显着放大，主要是由天文海潮引起的，例如水位变化和水动力流。这些因素可能会显着影响管道配置并显着增加内力。而且，与重力和铺设张力相比，洋流引起的载荷具有根本不同的性质。它们沿管道轴线不均匀分布，并在整个铺设过程中随着管道的非线性变形而改变它们的值和方向。本文提出了一种可行的数值方法，用于对安装中的管道静态配置进行结构分析，该方法受到非均匀分布、位置和方向相关的载荷和水位变化的影响。该方法将部分悬挂和部分铺设在海床上的整个管道视为单个连续管段，对 S 型铺设和 J 型铺设技术均有效。数值解采用管道有限差分离散化，并按照实际的管道铺设过程以增量方式依次进行。在每个长度增量处，通过一致最小化更新后的总势能来评估新的后续平衡配置，这允许考虑从动载荷，随着管道的非线性变形改变它们的值和方向。进行代表性参数研究以证明该方法的可行性。考虑了幂律电流速度随深度变化的剖面和水位变化的影响。该方法与 Abaqus/AQUA 相比，其收敛性通过有限差分网格细化得到验证。