两起船舶碰撞事故的调查和思考

基于对两起船舶碰撞事故的调查,分析导致碰撞发生的各种因素,指出当值船员责任心差和对航行规则的误解是导致事故发生的根本原因,提出船东应对船员进行有针对性的培训,以提高船员的工作责任心和工作技能,以期避免类似事故的发生。     

基于分组优化和矩阵运算的自动排课算法

为解决目前高校自动排课系统设计复杂、排课效率低的问题,提出了一种基于分组优化和矩阵运算的自动排课算法.该算法首先对课时段进行分组优化,然后引入矩阵的迭加匹配运算,最终实现自动排课.结果表明,该算法能高效、快速、优化地实现自动排课,并简化了程序的复杂性.     

基于ARPA与AIS的船舶避碰问题的思考

分析了两种流行的船舶避碰手段雷达ARPA与AIS,并给出一些合理对策或注意点,具有较好的参考价值,     

Nonlinear numerical analysis and progressive damage assessment of a cable-stayed bridge pier subjected to ship collision

Despite many studies on barge collisions with girder bridges in the literature, this paper investigates the progressive damage behaviors and nonlinear failure modes of a cable-stayed bridge pier subjected to ship collisions using finite element (FE) simulations in LS-DYNA. The damages in the pier initiate with appearing of local shear failures in the slender columns during the ship collision stage and reach the severe cross-sectional fractures associated with the formation of plastic hinges which causes the combined shear-flexural failures during the free vibration phase of the pier response. In addition, an analytical simplified model with two-degree-of-freedom (2-DOF) is proposed to formulate the strain rate effects of the concrete materials as the dynamic increase factors in the global responses of the impacted pier. It is found that the analytical model is able to efficiently estimate the impact responses of the structure compared to those from the FE high-resolution simulations. Moreover, three different damage indices are proposed based on the pier deflection, the internal energy absorbed by the pier, and the axial load capacity of the pier columns to classify the damage levels of the pier. Finally, an efficient damage index method is determinant by comparing the calculated results with the damage behaviors of the pier observed from the FE simulations.     

基于BIM的综合交通枢纽管线综合设计研究——以京张高铁清河站设计为例

随着时代的发展,土地集约利用已成趋势,综合性交通枢纽越来越多。在设计中,交通枢纽建筑具有功能多样、专业繁多、接口复杂的特点,为保证其不同空间效果和功能使用要求,综合管线设计越来越重要。从综合管线设计原则出发,结合京张高铁清河站管线综合设计实例,阐述综合管线一体化设计的思路和重难点。并以BIM技术在碰撞检查、验证复杂空间、解决净高、优化设计、三维交底5个方面的优势,分析BIM辅助设计的必要性。最终说明综合管线排布可以保证建筑空间的合理利用并从工序上指导施工:通过BIM技术深化设计,对提高设计准确性,提升管线施工效率和安装质量有重要的意义,为综合交通枢纽管线综合设计提供借鉴。     

基于粒子群-遗传优化算法的船舶避碰决策

为能在开阔水域中提升船舶驾驶员在多船会遇场景下的避碰决策能力,按照国际海上避碰规则(Convention on the International Regulations for Prerenting Collisions at Sea,COLREGs)的要求,综合考虑船舶航行的安全性与经济性,提出一种基于粒子群-遗传(Partide Swam Optimization-Genetic Algorithm,PSO-GA)的混合优化避碰决策算法。基于最近会遇距离(Distance of Close Point of Approaching,dCPA)和最近会遇时间(Time to Close Point of Approaching,tCPA)确定船舶碰撞危险度(Collision Risk Index,ICR)的计算方法,基于转向幅度与航行时间建立避碰决策目标函数。基于PSO-GA算法具有提高收敛精度和加速全局寻优的特点,当ICR≥0.5时,启动PSO-GA算法,获得让路船舶在全局范围内的最佳转向幅度和在新航向上的航行时间。仿真结果表明:与单独使用PSO或GA算法相比,PSO-GA算法能够以较少的迭代次数找到安全经济避碰航线。提出的避碰决策算法能够为船舶驾驶人员在避碰决策中提供参考,有助于提升船舶航行的安全性和降低船舶碰撞事故发生的风险。     

Dynamic responses analysis of a 5 MW spar-type floating wind turbine under accidental ship-impact scenario

Ship impact against offshore floating wind turbine (OFWT) has been identified as one of the major hazards with the development of OFWTs. The dynamic responses of OFWTs under ship impact should be taken into consideration during the design phase. This paper addresses a study on the dynamic responses of an OFWT in ship collision scenarios. Firstly, a mathematical model for external mechanism of ship-OFWT collision scenario is developed. Secondly, this model is combined with an in-house programme, DARwind, which can be used to predict nonlinear dynamic responses of whole OFWT system in time-domain. With the newly combined analysis tool, simulation cases for different scenarios are conducted to investigate the nonlinear dynamic responses of OFWT system, including the cases of still water condition, wave-only condition and wind-wave condition. It is shown that in still water condition, the ship impact will more obviously change the responses of motions and mooring system, compared with those in wave and wave-wind conditions. In the wave-only condition, these motions responses of platform are suppressed by wave effect, but the tower vibration and tower top deformation are sensitive to ship collision. For the wave-wind combined condition, the motions increment in surge and pitch due to ship collision becomes smaller than that of wave-only condition, but yaw motion has a considerable variation compared with those of the other two conditions. Additionally, the blade tip deformation increment due to ship collision are analyzed and it is found that the edgewise tip deformation got more obvious increment than that of flapwise. To further asses the safety of OFWT, the acceleration at nacelle are analyzed because some equipment might be sensitive to acceleration. The analysis results indicate that even though the OFWT structure doesn't get critical damage by ship impact, the equipment inside may still fail to work due to the high value of acceleration induced by ship impact. The research outcomes can benefit the safety design of OFWT in the engineering practice.     

基于Ls-dyna的船舶与码头碰撞动力特性仿真分析

运用非线性显式有限元的方法,分析船-码头碰撞的全过程,探讨碰撞部位对船舶动力特性的影响规律,揭示船-码头碰撞过程中船体构件的受损情况,预报碰撞力及变性能的时程变化规律。研究表明:船舶与码头发生首碰、尾碰时,船舶主要受力构件、受力特点明显不同,主要受力构件的应力分布特点是分布面积小,维持时间长,应力数值大;次要受力构件的应力分布特点是分布面积大,维持时间较短,应力数值小性。船舶与码头碰撞过程中伴有船舶的凹陷及船体外板的运动,在实际工程中应当给予足够的重视。     

Ship resistance in random ice field of small ice floes made of the substitute material北大核心CSCD

［Objectives］This study focuses on the feasibility of a ship resistance model test in an ice field of small ice floes made of substitute material in order to reveal the resistance components and thereby provide technical support for the design of ice-going ships. ［Methods ］ Ship resistance test in ice floes made of polypropylene (PP) instead of natural refrigerated ice is conducted. By adjusting the sizes, shapes, numbers of ice floes, the random ice field with a given concentration is generated. The geometric phase transition theory predicts that there exists a critical concentration which divides the random ice field into discrete phase (concentration is less than critical value) and connected phase (concentration is greater than critical value). ［Results］The main components of ice resistance in the discrete phase are open water resistance and ship-ice collision resistance, while ice resistance in the connected phase includes ice friction resistance, open water friction resistance and collision resistance. If the fractal dimension of the random ice field is used to redefine the ice resistance coefficient, it is nearly constant in the trial range (speed 0.3–0.9 m/s) when the concentration is smaller than the critical value. When the concentration is greater than the critical value, the ice friction resistance is inversely proportional to speed. ［Conclusions］Polypropylene can replace frozen ice in the prediction of ice resistance. The pure ice resistance of an ice field is divided into two components: ice resistance arising from collision and ice friction resistance arising from accumulation. © 2022 Journal of Clinical Hepatology. All rights reserved.     

基于状态空间采样的高速公路智能网联车辆轨迹动态规划

为实现智能网联车辆在高速公路动态行车环境下的轨迹实时规划，提出一种基于状态空间采样的轨迹动态规划方法。首先，以安全性为原则选取主车当前行驶的理想车道。基于Frenet坐标与笛卡尔坐标的转换关系，建立车辆运动横、纵向解耦的独立积分系统。将高速公路常见的行驶状态分为车道保持与定速巡航、变道以及前车跟随3类，预测主车行驶车道并针对3类行驶状态分别设计轨迹终端的目标配置方法。然后，利用多项式函数生成连接初始配置和目标配置的多条待选轨迹。构建考虑轨迹偏离理想车道程度、始末速度变化、规划周期和轨迹舒适性的综合损失函数，结合速度、加速度、曲率检查来评价各条待选轨迹的成本并进行排序。最后，预测车辆的横、纵向运动轨迹并构建一种胶囊形的车辆虚拟安全边界，通过碰撞检测，确定主车的最优轨迹，设置动态规划触发条件及时更新最优轨迹并避免过度规划浪费资源。研究结果表明：提出的算法能满足高速公路场景的动态规划需求；通过对轨迹规划周期、虚拟安全边界、动态规划时间间隔等关键参数的分析与优化，主车的横摆角速度范围稳定在-0.1~0.15 (°)·s^-1，横向加速度范围稳定在-0.16~0.32 m·s^-2，跟踪参考轨迹的最大误差不超过0.022 m，提出的算法能规划出具有高安全性、稳定性和舒适性的轨迹。