强夯技术在广西防城港软土地基处理中的应用

强夯技术在软土地基处理中是一种经济可靠的方法。文章介绍了将强夯技术应用于广西防城港市滨海西路A标工程软土地基处理中的设计、施工方案及加固效果,为类似地基处治工程提供参考。     

体外预应力对简支梁桥冲击系数影响的研究

通过对普通简支梁桥冲击系数计算方法的分析入手,对体外预应力结构加固后的简支梁桥冲击系数计算方法进行了研究。通过两者的对比,得出体外预应力结构对简支梁桥冲击系数的影响。同时指出了在应用体外预应力方法进行桥梁加固时,应对加固后各构件的振动特性进行分析,以免各构件因共振等原因发生破坏。     

山区河湾路基边坡颗粒起动条件与抗冲刷坡度计算

根据山区河湾路基边坡冲刷特点,建立路基边坡上填料单颗粒三维受力模式,对凹岸路基路边坡填料颗粒冲刷起动的基本条件进行理论推导。通过算例结果分析,探讨不同水流近底流速条件下的凹岸路基边坡抗冲稳定坡度。     

高原铁路电子元器件应用标准探讨

通过调研高原环境的特点,分析了高原特殊环境对电子产品元器件的影响,提出了针对高原环境提高元器件可靠性的要求和措施.为了保证电子产品及其元器件应用的可靠性,本文还提出了电子产品应用时需要考虑的各种措施和要求.     

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.     

Assessment of submarine pipeline damages subjected to falling object impact considering the effect of seabed

Untrenched submarine pipelines lying on the seabed are vulnerable and can be damaged by the impact of falling objects. This may cause significant economic costs for repair and even environmental contamination in case of rupture and oil leakage. This paper presents assessment of submarine pipeline damage subjected to falling object impact considering the effect of seabed through nonlinear explicit dynamic finite element modelling. The numerical model was first verified against existing experimental results and established studies. A total of 209 cases of parametric study was then conducted to assess pipeline damage by accounting for various factors, including object mass, velocity and seabed conditions. The results show that the pipeline damage can be directly related to the impact kinetic energy of the falling object for pipelines sitting on rigid bed. In other words, falling objects with the same impact energy (while mass and velocity may vary) cause the same damage to a pipeline. For a pipeline on a soil seabed, however, this study shows that pipeline damage is no longer simplistically determined by the impact kinetic energy of the falling objects. Falling objects with different mass and velocity may cause different pipeline damages, even though the impact energy is the same. It is interesting to find out that objects with a smaller mass (i.e. higher velocity) tend to cause greater damage than objects with a greater mass (i.e. lower velocity), when the total impact kinetic energy of the falling objects is the same. These observations are explored in this paper, which is explained with the variation of the energy absorption due to the existence of soil seabed.     

Modelling of wheels and rail discontinuities in dynamic wheel–rail contact analysis

A classification of wheel–rail contact is given. Difference is made between modelling of a running wheel with continuous single-point-contact, as is common practice in wheel–rail contact analysis, and a wheel with transient double- or multi-point-contact, which may occur for rail irregularities with curvatures larger than that of the wheel circumference. It is shown that application of the first model for these irregularities will strongly underestimate the contact forces as it does not describe occurring mechanisms correctly. Further, it is shown that in principle it is not possible to describe the second type of contact fully correct with a lumped wheel model. Both wheel models are formulated mathematically for some basic contact cases. Afterwards, results are applied to a linear track model. Analytical closed-form solutions are found in the frequency domain for arbitrary type of contact and numerically transformed to the time domain. Finally, the necessity is shown to avoid situations where transient multiple-point-contact may occur (like rail joints) in practice.     

DCT直线型换挡动力学仿真（续1）

为了使汽车冲击度和离合器滑摩功能够满足换挡品质的要求,文章对装有双离合器自动变速器（DCT）的汽车进行了动力学仿真分析,建立其变速器动力传动系统模型。并针对变速器直线型换挡过程中冲击度和滑摩功难以同时达到最优的问题,采用遗传算法对离合器油压值进行优化控制,获得油压-时间的最优控制曲线,将优化后的控制曲线代入仿真模型,结果表明,冲击度和滑摩功均达到较为理想的状态。     

Improvement actions for reducing transport’s impact on climate: A shipper’s perspective

The purpose of this paper is to compare improvement actions for reducing transport’s impact on climate from the shipper’s perspective. To that end, it introduces an evaluation tool for comparing improvement actions in transport systems in terms of transport costs, impact on climate, and barriers to implementation. Within the context of five international flows involving a food producer, three actions—namely, engaging intermodal transport, increasing load factors by double-stacking pallets, and using high-capacity vehicles—were evaluated. Shipment data were collected to calculate reductions in transport costs and impact on climate, whereas interviews with the food producer were conducted to identify barriers. Results showed that reductions in transport costs and impact on climate attributed to the improvement actions differed among the five flows. Engaging intermodal transport reduced the system’s impact on climate by 27–53%, double-stacking pallets by 0–23%, and using high-capacity vehicles by 7–15%, with differences primarily due to different freight densities. Concerning barriers to implementation, the improvement actions also varied by flow. Altogether, unlike other papers, which have examined improvement actions separately, this paper offers an evaluation tool for comparing several improvement actions at once, as applied to a particular empirical case. Shippers with multiple flows and several possible improvement actions can use the evaluation tool to efficiently reduce their systems’ impact on climate.     

钢轨波浪形磨损研究

钢轨波浪形磨损（简称钢轨波磨）是车辆与轨道结构激烈振动并产生噪声的主要因素之一，不仅影响旅客乘坐舒适度和装运货物的完好，而且缩短结构部件的使用寿命。结合试验，采用车辆一轨道耦合动力学理论、轮轨三维非赫兹滚动接触理论、材料摩擦磨损理论和塑性理论，研究钢轨波浪形磨损的形成和发展机理。主要研究内容如下。