非线性混合海况下近海风机塔筒底部载荷的动力响应

本文主要研究在非线性混合海况(即风浪和涌浪组合海况)下,以NREL 5MW_Baseline Monopile近海风机为研究对象,对其塔筒底部(基线)所受到的剪力和弯矩载荷的动力响应进行仿真。在近海风机的时域仿真中,选用了Ochi-Hubble六参数波浪谱,并编制了该谱的程序嵌入到FAST中进行编译。计算过程中,共进行了20次10 min的仿真分析。对于得到的短期载荷,给出了波高程,塔筒底部首尾向剪力和弯矩在线性与非线性不规则波作用下的时程曲线对比图。采用分块最大值法对每一次的短期载荷提取极值,并基于20次仿真所得的极值,给出了塔筒底部首尾向剪力与弯矩在线性与非线性不规则波作用下的超越概率曲线对比图。研究表明,在非线性混合海况下进行近海风机塔筒底部载荷的动力响应研究,计算结果对工程实际应用具有指导意义。     

Short-term statistics of ice loads on ship bow frames in floe ice fields: Full-scale measurements in the Antarctic ocean

Ship operation and ice loading in floe ice fields have received considerable interest during recent years. There have been several numerical simulators developed by different institutes which can simulate ship navigation through floe ice fields and estimate ship performance and local ice loads. However, public data obtained from full-scale measurement covering comprehensively ship performance and ice loads under various ice thicknesses, concentrations and floe sizes are rare. The 2018/19 Antarctic voyage of the Polar Supply and Research Vessel (PSRV) S.A. Agulhas II gathered considerable data of the ship in floe ice fields under various thicknesses, concentrations, and floe sizes. The aim of this paper is to carry out statistical analysis to seek suitable probability distributions which adequately fit the measured ice load and therefore suitable to be used as parent distributions for long-term estimation. For this aim, three categories of probability distributions, namely standard distributions, truncated distributions and mixture distributions are tested. It is found that truncated distributions can fit the load data better than standard distributions bounded at the threshold. In addition, mixture distributions are shown to have promising features, which fit the data well and are able to separate distribution components. Subsequentially, the well-performed distributions are used as parent distributions to make long-term load estimations. The estimation results demonstrate that long-term estimations are sensitive to the selection of parent distribution, which addresses the importance of finding correct distribution to model short-term ice loads. The data of ten selected cases will be published for the use of other researchers.     

基于轨道极限状态法的过渡板受力分析和配筋设计研究

京张高铁官厅水库特大桥为简支拱型大跨度钢桁梁桥,为防止梁端转角或错台量过大,降低梁端扣件系统受力,梁缝处设计采用了过渡板结构。为保证过渡板设计合理性和安全性,建立过渡板有限元实体模型进行受力分析,并首次运用轨道极限状态法对过渡板结构进行配筋设计。分析表明:(1)温度梯度作用对过渡板(420 mm厚)受力影响较大,在设计荷载中占据主导因素,在正温度梯度下,过渡板底部弯矩达到124.155 kN·m/m;(2)过渡板底部纵向弯矩在荷载基本组合作用下达到最大值,且实配配筋率最大,配筋时应注意以裂缝宽度为控制指标进行设计。     

快速重载运输趋势下的城轨车辆技术发展特征

随着城市化的进程,城轨交通客流强度不断增大,发车间隔不断压缩,使得我国城轨交通呈现出快速、重载、智能的发展趋势。文章结合我国目前城轨车辆快速、重载的发展状况,提出城轨车辆最大轴重的概念和建议值,且应按最大轴重对承载结构件进行设计,详细分析了城轨车辆结构件的技术发展特征,并建议应及时检测和维护车轮和钢轨,降低车、轨的振动和噪声,以提高车、轨的综合使用寿命。     

单叶片螺旋钢桩竖向承载特性数值分析

为分析单叶片螺旋钢桩在砂土地层竖向抗压承载特征,结合单叶片螺旋钢桩现场静载试验进行有限元软件模拟。将数值计算结果与现场实测数据进行对比分析,验证其数值计算结果的可靠性,其次采用该有限元软件分别模拟不同相对密实度砂土中几何参数不同的单叶片螺旋钢桩静载试验而得到不同荷载-位移曲线,同时将螺旋叶片直径的5%位移值对应荷载作为桩极限承载力。考虑砂土相对密实度,钢桩埋深,螺旋叶片直径,中心钢轴4个参数变化对单叶片螺旋钢桩极限承载力影响。结果表明:单叶片螺旋钢桩桩周土层的相对密实度和桩埋深是影响承载力的主要参数,螺旋钢桩叶片直径影响次之,钢轴直径的影响最小;同时,单叶片螺旋钢桩极限承载力增量百分比在松砂中最大,中密砂次之,密砂最小。     

Equivalent design pressure for ship plates subjected to moving slamming impact loads

When a ship navigates at sea, the slamming impact can generate significant load pulses which move up along the hull plating. The effect of the moving pressure has so far not been explicitly considered in the Rules and Regulations for the Classification of Ships. Based on a modal superposition method and the Lagrange equation, this paper derives analytical solutions to study the elastic dynamic responses of fully clamped rectangular plates under moving pressure impact loads. The spatial variation of the moving slamming impact pressure is simplified to three types of impact loads, i.e. a rectangular pulse, a linearly decaying pulse and an exponentially decaying pulse. The dynamic responses of fully clamped rectangular plates under the moving slamming impact pressure are calculated in order to investigate the influence of the load pulse shapes and moving speed on the plate structural behaviour. It is found that the structural response of the plate increases with the increase of the moving speed. The response of the plate subjected to a moving pressure impact load is smaller than the case when the plate is subjected to a spatially uniform distributed impact load with the same load amplitude and load duration. In order to quantify the effect of the moving speed on the dynamic load, a Dynamic Moving Load Coefficient (DMLC) is introduced as the ratio between the dynamic load factor for the moving impact load and that under the spatially uniform distributed impact load. An expression for DMLC is proposed based on analyses of various scenarios using the developed analytical model. Finally an empirical formula which transforms the moving impact loads to an equivalent static load is proposed.     

重载交通沥青稠度指标的应用研究

采用新型沥青稠度仪,对国内常用的几种基质沥青、相应的改性沥青以及掺加添加剂的沥青进行了稠度试验,并对稠度试验结果和其他高温指标试验结果做了比较分析,结果表明稠度可以作为评价沥青的高温指标,尤其是作为改性沥青的补充评价指标。     

基于企业网的分布式入侵检测系统的设计与实现

结合独立分析、独立存储和建立安全区的方法，提出一种新型高效、自身安全性好并且满足现代企业网络要求的分布式入侵检测系统的设计方法，该设计方法能够直接融入现有的分布式入侵检测系统或产品中，并且具有动态可扩展性。     

列车蓄电池箱的有限元分析和实验测试

通过有限元建模，对列车电池箱进行冲击载荷的有限元分析，得出各个方向冲击应力和箱体变形，并和实验数据进行比较，为进行电池箱的优化设计提供参考。     

不平整路面上的汽车动荷载

考虑汽车侧倾因素在路面不平引起汽车动荷问题中的影响,建立了4自由度车辆模型,并据此模型实例分析计算了在路面波幅一定的情况下,汽车在不同波长路面上以不同车速行驶时产生的车辆动荷载。