公路几何设计与交通安全

论述了公路几何设计对交通安全的重要性,从平面、纵断面、横断面、平纵横组合及视距等方面对安全做了分别阐述。     

Variation of whitecap coverage with wave-field conditions

Field observations were carried out at a sea observation tower to investigate how whitecap coverage on the ocean surface responds to wave-field conditions. Images of whitecaps were taken for every 4 h or 7 h in the daytime using a 3CCD digital video camera fixed at 14 m elevation, and they were stored automatically in a hard disk video recorder at a time interval of 1 s. The determination of whitecap coverage was made by means of a digital image processing. The 1/3 power of whitecap coverage increases linearly with increasing the 10-m neutral wind speed. On the basis of the deflection angle between the propagating directions of wind waves and swell, wave-field conditions are classified into four cases. The present results show that whitecaps are produced most actively under the condition of the pure windsea and they tend to be suppressed by the presence of swell. It is difficult to find a certain relation between the deflection angle and whitecap coverage. Whitecap coverage also increases with the wave age in the same wind-speed conditions.     

基于货舱改进后的货船总纵强度分析与研究——以鑫兴10甲板货船为例

文章以改进后的鑫兴10甲板货船为例,对增加了两个舱后的船体进行总纵强度分析。在进行强度分析过程中,首先采用澳大利亚的Maxsurf软件计算不同工况下的静水弯矩。进而把静水弯矩施加到该船的货舱区域,同时利用有限元分析软件MSC.Nastran进行强度校核,得到了总纵强度的计算步骤和结论,同时保证了鑫兴10甲板货船建造的顺利完成。     

Axial vibrations of a propulsion system taking into account the couplings and the boundary conditions

Calculations of the axial vibrations of a marine power transmission system are a very difficult problem owing to the complicated couplings and difficulties in determining the boundary conditions. The torsional–bending–axial coupling action of the system should be accounted for when considering its dynamics. A determination of the mutual interference of system vibrations and their boundary conditions is also necessary. A performance analysis of the main engine bearings, the thrust bearings, and the axial dampers should also be carried out. Thus, the effects of additional bending stresses in the crankshaft and possible vibrations of the ships structure due to the reaction force in the thrust bearings should be considered. I have devised a computer program to analyse the axial vibration problem. The numerical analysis method presented is compared with measurements (performed on real ships) and verified by them.     

高墩水平温差对连续刚构桥上无缝线路的影响

为研究高墩水平温差对桥上无缝线路的影响,选取某高墩大跨连续刚构桥工程实例,基于梁轨相互作用原理,建立线桥墩一体化有限元模型,分析在水平纵向和横向温差作用下高墩大跨桥上无缝线路受力变形情况。结果表明:高墩纵向温差对连续刚构桥上无缝线路纵向受力影响较大,随着桥墩纵向温差的增大,桥上无缝线路受力逐渐增大;桥墩横向温差影响桥上无缝线路平顺性,当桥墩横向温差超过一定的限值时,连续刚构桥上无缝线路会出现长波不平顺超限;总结以上分析结果,建议在连续刚构桥上无缝线路设计检算中考虑高墩在水平温差作用下对桥上无缝线路的影响。     

浅谈近岸、浅海海域波浪对船舶的危害——A轮沉没引发的思考

近岸,浅海海域的波浪与深海海域的波浪性质相异,航海驾驶人员必须特别重视,以防其造成船舶的浪损或更严重的海事发生。     

舰船波浪弯矩响应的频率特性

非直壁式舰船在高浪级和高航速下的弯矩响应中,除了含有低频遭遇频率成分外,还存在着一定数量的遭遇频率的倍频成分及船体各谐调的垂向总振动频率成份,它们都会对舰船波浪弯矩的非线性响应产生相应的影响。如果舰船的第一谐调垂向总振动频率正好是遭遇频率的整数倍,这时弯矩的非线性响应将达到极值。本文从模型试验及理论计算两方面分析了舰船波浪弯矩的频率特性,对船体载荷响应理论的发展及设计载荷的确定具有指导意义。     

集装箱船整船有限元结构分析

文章以一艘１７００箱集装箱船为例,阐述了整船有限元结构分析方法。先建立全船有限元模型和质量模型,再用三维流体动力计算程序进行波浪随机载荷的长期预报,并在此基础上导出设计波参数组,最后,在全船有限元模型上 计算得出船体结构在各个设计波上的应力分布和变形结果,所得到的船体结构有限元分析结果对同类型集装箱船的设计和强度分析有一定的参考价值,对其它类型的船舶结构强度分析也有一定的借鉴意义。     

Semi-submersible wind turbine hull shape design for a favorable system response behavior

Floating offshore wind turbines are a novel technology, which has reached, with the first wind farm in operation, an advanced state of development. The question of how floating wind systems can be optimized to operate smoothly in harsh wind and wave conditions is the subject of the present work. An integrated optimization was conducted, where the hull shape of a semi-submersible, as well as the wind turbine controller were varied with the goal of finding a cost-efficient design, which does not respond to wind and wave excitations, resulting in small structural fatigue and extreme loads.The optimum design was found to have a remarkably low tower-base fatigue load response and small rotor fore-aft amplitudes. Further investigations showed that the reason for the good dynamic behavior is a particularly favorable response to first-order wave loads: The floating wind turbine rotates in pitch-direction about a point close to the rotor hub and the rotor fore-aft motion is almost unaffected by the wave excitation. As a result, the power production and the blade loads are not influenced by the waves. A comparable effect was so far known for Tension Leg Platforms but not for semi-submersible wind turbines. The methodology builds on a low-order simulation model, coupled to a parametric panel code model, a detailed viscous drag model and an individually tuned blade pitch controller. The results are confirmed by the higher-fidelity model FAST. A new indicator to express the optimal behavior through a single design criterion has been developed.     

Wave spectrum estimation conditioned on machine learning-based output using the wave buoy analogy

In this work, a hybrid approach for wave spectrum estimation is proposed. Fundamentally, the approach is based on the wave buoy analogy, processing ship response measurements, via a framework combining machine learning and a physics-based method dependent on available transfer functions. Specifically, a non-parametric (Bayesian) estimate is obtained of the directional wave spectrum conditioned on integral wave parameters established by a convolutional neural network. The developed method is assessed in a case study considering about two years of data obtained from an in-service container ship. The method produces good results, significantly improved when compared to the initial estimate made without constraints.