近场地震速度脉冲下的反应谱加速度敏感区

已有的地震记录表明,含有速度脉冲的近场地面运动往往会具有较大的PGV PGA比值,进而会在反应谱中产生较宽的加速度敏感区。所以含有速度脉冲的近场地面运动会显著地改变结构的响应特点,使结构产生较大的内力和位移,同时对结构的延性要求也会加大。对三条来自Chi chi地震的脉冲型近场地震记录和一条Imperialvalley地震的一般记录的响应特点作了简单分析,并应用ANSYS有限元计算程序,通过对四个桥墩模型的时程分析发现,桥墩在含有速度脉冲的近场地震激励下,会产生相对较大的墩底内力和墩顶位移。从三个方面加强了对近场地震的设防,较为合理地解决了近场地震的设防问题。     

Improved velocity estimation using single loop detectors

This paper develops an improved algorithm for estimating velocity from single loop detector data. Unlike preceding works, the algorithm is simple enough that it can be implemented using existing controller hardware. The discussion shows how the benefits of this work extend to automated tests of detector data quality at dual loop speed traps. Finally, this paper refutes an earlier study that found conventional single loop velocity estimates are biased.     

粒径对块石层自然对流特性影响的试验研究

用粒径为5～8,8～15和15～20 cm的3种块石分别填筑成块石层模型,在实验室内研究它们的空气自然对流特性。结果表明,在块石层模型下表面保持20℃而上表面从20℃降至-20℃的过程中,模型内均产生了Benard流,而且模型内空气自然对流的强弱与块石的粒径有关,粒径为15～20 cm的块石层模型内气流速度最大,约为2.2 m.s-1;粒径为8～15 cm的最小,约为1.5 m.s-1,这种变化主要是由块石层内热弥散效应以及块石与空气间接触面积的改变而引起的。控温方式对空气自然对流影响的研究表明,由模型上表面降温所产生的空气自然对流效应强于在块石层模型下表面升温,故在实际工程中,冬季块石层内的空气自然对流更易于发生。针对模型内空气流速计算值均比实测值小的问题,建议在进行多孔块石结构对流换热理论计算时,应考虑块石层模型的假设条件、热弥散作用、流动惯性以及空气热物性随压力的变化等的影响。     

汽车减振器弹簧阀片变形模型的研究

对圆环薄板的von Karman方程，采用钱氏摄动法求解，给出确定减振器弹簧阀片大挠曲变形任意阶摄动解的方法，并应用二阶摄动解进行了减振器速度特性的仿真计算。为验证仿真结果，进行了减振器速度特性的台架试验。结果表明：仿真结果和试验结果有很好的一致性。     

自动化驼峰速度控制方法比较及应用

驼峰溜行车组的速度控制是保证驼峰解体作业安全和提高驼峰调车场解体效率的重要环节。本文简要介绍了现行的驼峰速度控制方法，并比较了两种控制方法的优缺点，然后提出了一种对制动力可调的减速器的新的控制方法及应用。     

基于PIV技术的明渠非恒定流试验系统

建立了一套高精度的明渠非恒定流试验系统,通过计算机及变频器控制水泵转速产生非恒定流过程,由电磁流量计、超声水位计实时监测流量和水位变化过程,并通过PIV流场仪进行流场测量。该系统不但能生成连续、稳定的周期性非恒定流过程,很大程度改进了明渠非恒定流的试验手段。     

An experimental/numerical approach for evaluating skin friction on full-scale ships with surface roughness

For an accurate evaluation of the increase in skin friction due to various surface topographies on ships, i.e. plate roughness, coatings, or bio fouling, both experimental measurements and a numerical evaluation of those measurements are necessary. The measurements are necessary as no other practical method exists to evaluate the skin friction coefficient on most surface topographies, and numerical evaluation is required to compute the roughness effects of varying ship types and speeds. Therefore, a method for measuring the skin friction coefficient for bio-fouled and structured surfaces at full-scale friction velocity is presented, and a validation of the design and measuring procedures is given. For the ship frictional resistance calculations, the Computational Fluid Dynamics (CFD) code ShipFlow has been modified to take the added friction into account.     

自升式海上风电安装船的模型试验分析研究

主要阐述了具备自航能力的自升式海上风电安装船在船型设计阶段的模型试验和计算分析,为相似船型和类似海洋工程装备的设计研究提供了参考.     

Load effects on vessel-shaped fish cage steel structures,nets and connectors considering the effects of diffraction and radiation waves under irregular waves

Vessel-shaped fish cages are mainly composed of a large floating body, aquaculture nets and a number of steel frames. Due to the large scale of vessel-shaped fish cages, the velocity field induced by the diffraction waves and radiation waves cannot be ignored in the calculation of the loads on the net and steel frames. In turn, the loads can affect the wave-induced response of the floating body and hence the radiation waves as well as the sectional forces. In this paper, a novel method is proposed to consider the coupling effect. First, considering the irregular waves in short-term periods, the global response of the floating body is calculated in the time domain by the state-space method based on potential flow theory. Meanwhile, the velocity field considering the influence of the floating body is built according to the velocity transfer function. Then, the Morison formula is used to calculate the loads on the nets and the steel frames. Finally, the coupling achieved through numerical iterations is considered in the calculation of the twine tension, load effect of connector and the global cross-section under irregular waves. It is found that the diffraction and radiation waves make a significant difference in the twine tension and connector load effect.     

Planar multibody dynamics of floating Y-method installation system and the lowering of subsea equipment based on finite element modeling

The subsea equipment installation is a complex operation that demands a precise and reliable approach to avoid the accidental losses of lives and equipment damage. The multibody installation system is overwhelmed with the dynamic behavior and responses of the system, which signifies the importance of analysis of the Multibody Dynamic System (MBDS). The modeling of MBDS is challenging and complicated due to the interconnectivity and nonlinearity assigned to them. In this paper, the planar dynamics of a floating multibody system are attained by employing two tugboats and a payload with a contextual offshore installation scenario to be applied in a water depth of over 1500 m. The lifting operation is nine degrees of freedom (9-DOF) multibody model done with the help of two strands and three bodies having 3-DOF each. The coupled equations of motion are established by deploying the Velocity Transformation Technique. The hydrodynamic and two-strand forces are simplified as linear, while the hydrostatic and mooring forces are treated as nonlinear external loads. The numerical solution to the equations for the MBDS is obtained from the Runge Kutta Method of Fourth-Order. Furthermore, the Finite Element Modeling approach discusses the installation operation using Y-method. The results of the proposed numerical model are validated by comparing it with the numerical simulation from OrcaFlex, and the results from both models are found to be in good agreement. The findings of this study will help improve the safe and stable installation of deep-water multibody structures.