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991.
桨毂是调距机构及桨叶等部件的安装基础构件,承受了较大的载荷.从桨毂受力的角度,模拟桨叶受力的加载重块离心力对叶根法兰中心产生的弯矩和离心力能有效模拟实际机构的推力弯矩、扭力弯矩、离心力和离心力扭矩,具备试验可行性.为评估试验误差,将有限元计算方法和试验结合应用,利用试验检验有限元计算的准确性,反之,有限元计算能有效评估... 相似文献
992.
近期,国内沿海散货运输市场对新型高效的国内航行散货船需求量增大。现以新开发的45000吨级散货船为例,介绍国内航行散货船的总体设计特点,并就如何绘制恰当的载货量曲线提出了建议。 相似文献
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Carolina Osorio Gunnar Flötteröd 《Transportation Research Part B: Methodological》2011,45(9):1410-1423
We present a dynamic network loading model that yields queue length distributions, accounts for spillbacks, and maintains a differentiable mapping from the dynamic demand on the dynamic queue lengths. The model also captures the spatial correlation of all queues adjacent to a node, and derives their joint distribution. The approach builds upon an existing stationary queueing network model that is based on finite capacity queueing theory. The original model is specified in terms of a set of differentiable equations, which in the new model are carried over to a set of equally smooth difference equations. The physical correctness of the new model is experimentally confirmed in several congestion regimes. A comparison with results predicted by the kinematic wave model (KWM) shows that the new model correctly represents the dynamic build-up, spillback and dissipation of queues. It goes beyond the KWM in that it captures queue lengths and spillbacks probabilistically, which allows for a richer analysis than the deterministic predictions of the KWM. The new model also generates a plausible fundamental diagram, which demonstrates that it captures well the stationary flow/density relationships in both congested and uncongested conditions. 相似文献
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以连霍高速拓宽工程中某T梁为例,利用ANSYS软件建立拓宽后T梁的空间有限元模型,研究在汽车荷载作用下不同连接方式对拓宽后桥梁结构的影响,提出新旧桥间不设置横隔板时桥梁整体和局部受力最为不利,建议采用新旧桥之间设横隔板而墩顶可不设置横隔板的横向连接形式。 相似文献
998.
分析了影响桥梁冲击系数的相关因素,对一种FRP轻便桥在车辆以不同速度通行时的动态响应进行了动载试验和动力分析。结合FRP轻便桥的动态试验结果和动力分析结果,给出了不同速度下FRP轻便桥的冲击系数参考值。对FRP桥梁的设计有一定参考意义。 相似文献
999.
The undrained bearing capacity of a spudcan foundation under combined loading in soft clay 总被引:1,自引:0,他引:1
Mobile jack-up drilling rigs are typically supported by individual, large diameter spudcan foundations. Before deployment, the suitability of a jack-up to a location must be shown in a site-specific assessment under loads associated with a 50-year return period storm, which ultimately need to be resisted by the foundations. The capacity of the spudcans under combined vertical, horizontal and moment loading is therefore integral to the overall site-specific assessment of the jack-up.In soft clays, spudcans can penetrate deeply into the seabed, sometimes up to several footing diameters, with soil flowing around the downward penetrating footing, sealing the cavity. Although this is generally believed to provide some additional bearing capacity to the footing, no detailed study or formal guidance is available to date. This study, therefore, investigates the influence of soil back-flow on the failure mechanisms and quantifies the effect on the capacity of a spudcan under general loading through finite element analyses. A closed-form analytical expression is developed that describes the capacity envelope under combined loading, applicable to embedment depths ranging from shallow to deep. 相似文献
1000.
Fatigue crack propagation in marine structures is obviously governed by mechanics of the considerably different four levels of multi-scale problems. Problems of structural response to environmental loads have length scale of several hundred meters, whereas possible detectable size of cracks from initial defects in a weld is of the order of millimeters. Once a fatigue crack initiates, crack tip plasticity is of the order of several grain sizes, while the resulting fatigue crack growth in each load cycle is of the order of nanometers. In our previous work, the first author and their associates have developed the so-called CP-System, which can treat the first two multi-level problems as an integrated system. Furthermore, we have incorporated the third level of mechanics by using the stress intensity range corresponding to the repeated tensile plastic deformation ahead of the crack tip. In the present paper, we shall discuss a more rational integral equation-based formulation in order to integrate the third and fourth levels of micro-mechanics to the first two levels of continuum mechanics.The method is then applied to fatigue crack propagation under the effects of random sequence of clustered loading. As an example of the random sequence of clustered load, we shall use the so-called “storm model”. In the crack propagation simulation, we have to take into account of the plastic wake on the crack surfaces, whose thicknesses are influenced by the material parameters involved in the crack growth model. These parameters are first identified by the fatigue tests under combined constant and random loading using a CT specimen. Then, fatigue crack growth is investigated by numerical simulation and fatigue tests for various random sequences of clustered loading. The experimental and numerical results agree quite well with each other, and fatigue crack propagation is found to be considerably retarded under random sequence loading, so that the conventional equivalent stress approach may provide rather conservative results to the real seaway loading. 相似文献