非通航孔桥墩自适应拦截网防撞装置实船拦截试验与水动力计算

针对非通航孔桥墩,研发了一种自适应拦截网防船舶撞击装置,主要由系泊大浮体、系泊锚链和固定锚、自适应小浮筒、拦截网、恒阻力缆绳以及触发钢索所组成。阐述了该防撞装置设计原理,即偏航船舶撞击该防撞装置,小浮筒会带动拦截网自适应地从水平状态竖起展开,包裹住来撞船首,再通过相连浮体的运动阻力和恒阻力缆绳来吸收船舶动能,拦截住船舶,保护非通航孔桥墩安全。随后介绍在福建平潭海峡大桥引桥附近海域实施的实船撞击自适应拦截网防撞装置的大型试验,试验结果显示:自适应拦截网成功升起,船舶被安全拦截,从而实验证实了设计原理与设计方案的可行性和可靠性。最后,采用大型水动力分析软件AQWA对防撞装置拦截船舶过程进行数值模拟,模拟结果与实验结果基本一致,说明了数值仿真具有较好的计算精度和可靠性,能够为该防撞装置的结构设计与优化提供重要的参考。     

浮式两级缓冲防撞系统及浮体结构构型研究

以浮式两级缓冲防撞系统为研究对象,介绍其工作原理,利用动力学分析软件LS-DYNA构建了碰撞模型并进行了仿真计算,依据仿真结果完成了以阻尼索组与浮体结构构型为主要内容的防撞系统设计。研究确定了阻尼索组的布置位置、材料及数量,为浮体内部结构构型设计了7种比选方案,分别对5 000 t船舶撞击浮体前梁和侧梁的动态过程进行了仿真分析,对比了不同方案及不同板梁厚度下的接触力。研究结果表明:浮体内部构造若选用板梁厚度12 mm的方案6设计,则碰撞发生时浮体前梁和侧梁分别可以稳定地提供10.4 MN和7.9 MN的均值力,以及11.5 MN和8.9 MN的峰值力,设计浮体能够满足整体刚度要求,防撞系统符合双保护原则。防撞系统及浮体结构构型设计为下一步全面开展船舶撞击防撞系统后的动力学响应分析奠定了基础。     

钻井船插桩对导管架平台群桩影响的CEL有限元分析

采用CEL大变形非线性有限元方法并结合非线性地基梁模型对海洋石油941钻井船在番禺10-2平台钻井插桩时对邻近导管架平台群桩的影响进行了分析,并得到以下结论:1)钻井船插桩过程中,桩身最大位移及出现的位置随钻井船插桩深度增加而下移且钻井船插桩位置与群桩距离越近,对桩的影响越大;2)在插桩过程中,桩身最大弯矩出现的位置与桩身最大位移出现的位置一致,而桩身最大剪力出现的位置较桩身最大弯矩出现的位置偏下;3)与没有插桩影响的群桩相比,桩身最大弯矩与桩身最大剪力明显增加。     

大直径钢管桩水平静载试验内力变形测试及分析

为解决在钢管桩水平静载试验中更加高效、安全和准确进行桩身内力变形测试和分析的问题,文章针对打入钢管桩中的应变传感器和测斜管分别提出实用且可靠的安装、保护和测试方法;将该方法应用于西非某码头工程,在大直径钢管桩水平静载试验中进行应力和变形测试。研究结果表明,该安装和保护方法实用且可靠,可保证水平试验过程中钢管桩的内力变形情况得到如实测试和记录,对研究分析大直径钢管桩受水平荷载时桩身弯矩和水平位移的变化情况意义重大,可为类似项目的设计和施工提供参考。     

海上风电单桩基础土相互作用特性影响因素分析

采用有限元软件ABAQUS建立了海上风电单桩基础与土相互作用数值计算模型,将波浪、洋流及风荷载等效成双向对称循环荷载,研究了水平循环荷载作用下不同因素对桩身水平位移、剪力和弯矩的影响规律。研究表明,随着循环荷载比的增加,桩身位移零点和桩身剪力反弯点沿埋深逐渐下移,桩身弯矩最大值点位于浅层土体;不同荷载频率时桩身位移在零点以上变化较大,桩身弯矩随着频率的增加逐渐增大;单向循环荷载作用下桩身位移最大,双向对称循环荷载作用下桩身位移最小;壁厚较小时对桩身水平位移影响较大;在位移零点之上范围内可以考虑设计"上厚下薄"的钢管桩,以减小桩身水平位移;不同桩壁厚时桩身剪力曲线在埋深约6D处出现交点,且泥面处桩身弯矩变化不明显。     

海上风机高桩承台基础船舶碰撞动力分析

为研究海上风机高桩承台基础受到船舶碰撞作用的动力响应,本文运用非线性分析软件LS-DYNA,结合我国东南某海上风电场实际情况,通过建立风机高桩承台基础与船舶碰撞的有限元模型,研究了船舶在撞击过程中的撞击力时程分布以及高桩承台基础在撞击作用下的响应,分析了船舶碰撞对于风机基础结构的动力影响,对于橡胶护舷对于基础结构的保护作用进行了分析。研究结果表明,船舶撞击速度对于风机基础结构的位移影响显著,需要严格控制船舶靠泊速度。同时,橡胶护舷对于结构起到了良好的保护作用。     

深水港斜顶桩驳岸结构后高回填桩土相互作用研究

斜顶桩驳岸结构是一种深水高桩码头接岸结构型式，驳岸结构后进行高回填将是一个复杂的被动桩与土相互作用的问题。采用平面有限元方法，分别建立了后支撑和前支撑斜顶桩驳岸结构的桩一土相互作用模型，桩基采用梁单元模拟，桩一土界面采用接触对进行模拟，进行了高回填施工过程的仿真分析。将承台侧向位移的数值计算结果与原型观测值进行了比较，吻合较好，并对桩身侧向位移、板桩前后土压力以及位移场进行了分析。结果表明：结构的变形随着施工过程进行而变化，承台最大侧向位移发生在施工过程中；不同驳岸结构的被动土压力分布相似，而主动土压力由于支撑桩的位置不同而有所差别；后支撑桩的桩身挠度相对较大。研究结论可为此类结构的设计及计算提供参考，也可为深水港结构型式的优化提供建议。     

大直径钢管桩水平载荷试验研究

文章首次对直径为2800mm 的超大直径钢管桩开展了单桩水平静载试验,研究分析了超大直径钢管桩的桩侧水平抗力、桩身截面弯矩、桩身水平位移与桩基水平荷载之间的变化曲线,得到了不同水平位移时桩周地基反力模量的变化规律,为超大直径桩基水平承载力设计提供了现场试验数据。     

坠物撞击管道实验装置设计与实验研究

针对船舶抛锚或海洋平台坠物对海底管线的撞击会对管道造成一定的危害,本文设计了坠物撞击管道的实验装置,并对实验装置进行了优化分析,在此基础上提出了可行的实验方案。通过ANSYS有限元软件对该实验装置进行了静力分析,确定了最终的装置结构形式,并开展了坠物与管道的撞击实验。该装置在实验条件下最大变形不足1mm,可满足实验要求。实验证明,随着撞击能量的增加,管道的损伤程度明显增大。本次实验研究结果为分析坠物对管道的撞击作用提供了研究基础。     

低速运动船只撞击埋置框架结构动力分析模型

通过引入合理的撞击模型,建立了水面运动船只低速撞击埋置框架结构的传递矩阵-节点耦合矩阵动力分析模型。该模型可模拟船只与结构在撞击过程中的短暂脱离,并分析撞击力时程曲线和整个撞击系统的动力响应。与有限元方法的比较验证了结构传递矩阵-节点耦合矩阵动力分析方法的有效性。不同于规范计算方法,分析发现撞击过程中的最大撞击力不仅与船只的初始动能有关,还受船只与结构间的接触刚度及结构的自身刚度影响,这两种刚度越大,则最大撞击力也越大,撞击持续时间则越短,而撞击力时程曲线的振荡越明显,甚至在船只撞击结构后的很短时间内就可能产生较大的撞击力峰值。     

Dynamics of ships and fenders during berthing in a time domain

When designing fixed or semi-fixed structures used for berthing ships, it is generally assumed that the entire kinetic energy of the ship is absorbed by the fender or the system of fenders. The fenders have the functions of ensuring a safe berthing both for the ships and the piers by absorbing shock loads and preventing direct contact between the berthed ship and the pier. In this study, the problem is analyzed in the stages of berthing, collision and leaving. Each of the stages is analyzed and solved in the time domain. The system is assumed to consist of three components: pier, fender and the ship. Environmental effects that simultaneously affect berthing are wave, current and wind effects. Cummins equation was assumed to be a good representation of the problem and was solved in time domain taking various factors into account. Nonlinear effects related to the instantaneous values of forces, moments and ship motions, which are time dependent, were studied by the Cummins equation and its later developments by Ogilvie. Fender forces were added to the calculation scheme by the authors. A case study for a passenger ferry operating in Izmir bay is presented.     

船舶碰撞中空夹层钢管混凝土导管架平台损伤分析

针对船舶与中空夹层钢管混凝土（CFDST）导管架平台碰撞问题,利用ABAQUS/Explicit非线性有限元软件建立中空夹层钢管混凝土导管腿导管架数值模型,对船舶碰撞进行数值模拟,对比分析1 m/s、2 m/s和3 m/s的3种碰撞速度下工况下导管架抗碰撞性能、耗能及损伤。从碰撞力、碰撞区域变形以及导管架能量耗散等方面详细研究中空夹层钢管混凝土导管腿作用下导管架整体的损伤模式和动力响应。结果表明：CFDST导管架在船舶碰撞荷载作用下主要由CFDST导管腿耗能,有效控制了结构整体位移变形,提升了整体刚度,有效发挥平台各构件之间组合耗能,结构抗碰撞能力得到明显提升。     

Safety Assessment of Buried Pipeline during Pile Driving Vibration in Offshore Engineering

To assess the impact of pile driving on adjacent submarine pipelines during the reconstruction of a pier berth, the local damage model of submarine pipelines is established to explore the safety thresholds of the particle peak velocity and horizontal displacement. The results are analyzed and adjusted by the existing standards and the corresponding literatures. Then, a three-dimensional numerical model is presented to assess the feasibility of the construction of piles by the obtained safety limits, in which the nonlinear behavior of the soil and stress–seepage coupling analysis are considered. After the construction, the safety of submarine pipelines is rechecked by the measured value of the particle peak velocity and horizontal displacement. Meanwhile, the propagation law of vibration, the horizontal displacement of underground soil, and the pore pressure during pile driving are explored. The results indicate that the construction of piles of 2# mooring pier did not cause damage to adjacent submarine pipelines. However, the construction of piles of 1# mooring pier which is nearer may cause damage to submarine pipelines.     

A Crashworthy Device Against Ship-OWT Collision and Its Protection Effects on the Tower of Offshore Wind Farms

At present,more and more offshore wind farms have been built and numerous projects are on the drawing tables.Therefore,the study on the safety of collision between ships and offshore wind turbines (OWT) is of great practical significance.The present study takes the advantage of the famous LS-DYNA explicit code to simulate the dynamic process of the collision between a typical 3MW offshore wind turbine model with monopile foundation and a simplified 2000t-class ship model.In the simulation,the added mass eff...     

Development of the collision ratio to infer the time at which to begin a collision avoidance of a ship

A prior study attempted to solve the intrinsic problem of a critical collision condition including the slower ship’s dilemma by considering the maneuverability of the own ship and the International Regulations for Preventing Collisions at Sea (COLREGs). The collision ratio proposed in the previous study provided insight into the solution of the intrinsic problem, but it was not suitable as an index to determine the time at which to begin the maneuver to avoid the collision.This paper develops a collision ratio as an index that can be used to determine the time at which to begin the collision avoidance maneuver. The collision ratio is calculated by considering the maneuverability of the own ship, the COLREGs, and three virtual intrusion domains (VIDs). The validity of the inferred collision ratio is then assessed according to the dynamic characteristics of the own ship and the basic knowledge of the collision avoidance algorithm. The results indicate that the proposed collision ratio is suitable for use as a new index to determine the time at which to begin the collision avoidance maneuver.     

Parallel trajectory planning for shipborne Autonomous collision avoidance system

Collision at sea is always a significant issue affecting the safety of ship navigation. The shipborne autonomous collision avoidance system (SACAS) has the great advantage to minimize collision accidents in ship navigation. A parallel trajectory planning architecture is proposed in this paper for SACAS system. The fully-coupled deliberative planner based on the modified RRT algorithm is developed to search for optimal global trajectory in a low re-planning frequency. The fully-coupled reactive planner based on the modified DW algorithm is developed to generate the optimal local trajectory in a high re-planning frequency to counteract the unexpected behavior of dynamic obstacles in the vicinity of the vessel. The obstacle constraints, ship maneuvering constraints, COLREGs rules, trajectory optimality, and real-time requirements are satisfied simultaneously in both global and local planning to ensure the collision-free optimal navigation in compliance with COLREGs rules. The on-water tests of a trimaran model equipped with a model-scale SACAS system are presented to demonstrate the effectiveness and efficiency of the proposed algorithm. The good balance between the computational efficiency and trajectory optimality is achieved in parallel trajectory planning.