共查询到20条相似文献，搜索用时 93 毫秒
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通过刚性模型风洞测压试验,研究了风向沿马鞍低点连线时菱形马鞍屋盖表面的风压特性.首先给出了屋盖表面的平均及脉动风压分布,通过脉动风压谱,从微观角度阐述了迎风前缘附近旋涡从生成、发展直到最后破裂的过程,进而解释了迎风前缘易损区域的平均及脉动风压分布机理.分析马鞍高点附近的风压谱形状,发现结构对于来流的干扰作用在风压脉动上体现为高频脉动.此后用测点风压时程的三、四阶矩对风压的非高斯特性进行描述并给出了划分高斯、非高斯区的标准,在此基础上对马鞍屋盖表面进行了分区.通过研究脉动风压谱,发现风压非高斯特性是由于来流的分离运动及结构对来流的干扰作用引起的,且前者引起的非高斯特性较后者更为显著. 相似文献
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考虑阻尼之组合结构的动内力局部效应修正 总被引：2，自引：1，他引：1
以往对结构进行动力分析常常忽略局部效应的影响,但实践证明,局放效应在某些结构中占有很大的比重,为得到精确的动力响应,必须考虑局部效应本文在已有的基础上,提出了考虑阻尼之组合结构在地震作用下局部效应的计算方法通过对结构动内力进行局部效应修正前后求解精度的对比,证明了考虑局部效应的重要性．最后,本文对核反应堆堆顶屏蔽给构进行了局部动内力分析,得出了一些有意义的结论。 相似文献
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南京奥体中心的观光塔为一高耸结构,其风荷载是必须考虑的问题之一.由于观光平台及观光塔本身形状的复杂性,建筑规范无法准确给出其风荷载,因此需要在风洞中进行测压测力试验,以测定观光塔整体及局部风载,获得风场数据.文章介绍了整个试验过程,并对试验结果进行分析,根据各风向角下的风压分布特征给出了结构抗风设计和考虑载人时的最不利风向角与最大风压值,可为观光塔结构强度设计、电梯间及观光平台的玻璃幕墙设计提供风荷载依据. 相似文献
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依据十堰市城区工程项目地震安全性评价工作中地脉动实测数据,以场地土动力特性和地脉动频谱结构为研究对象,对城区场地进行了地脉动的测试及频谱分析。并结合岩土工程勘察报告对工程场地的脉动频谱曲线进行了分类统计,结果表明地基土刚度变化与覆盖层厚度有关,卓越周期值的变化与场地地质条件相对应。为场地评价和工程抗震设计提供了依据。 相似文献
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针对艇尾伴流场中大侧斜桨无空化水动力和水声性能的尺度效应问题,对几何相似但直径分别为250,500和1000mm的七叶大侧斜桨的无空化线谱噪声及其标准化谱曲线经验公式和总声压级进行了分析.噪声预报同时采用频域和时域计算2种方法.作为脉动噪声源的桨叶表面脉动压力和法向速度分布由URANS模拟得到.结果表明,在相同进速系数下3种尺度桨的0.7R截面压力系数分布重合度高;3个桨的推力脉动均能准确地反映出轴频和叶频信息,且中桨相对于小桨在叶频处的推力脉动幅值增量较大桨相对于中桨要大.2种噪声预报方法得到的大桨相对于小桨的总声级增量相差2.49dB;大桨和中桨标准化谱曲线较为一致,但与小桨差异明显.随着直径的增加,线谱谱级和总声级增量增加.建议应尽可能增大模型桨的几何尺度,以减小经验公式的预报误差和尺度效应影响. 相似文献
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采用文献资料法、实地调查法,基于系统论视角探讨皖北地区体育产业发展动力机制,认为皖北地区体育产业发展动力机制面临规模扩大进程中要素供给的不足、质量需求下结构演化升级的动力不足、效应保障下产业融合的行动力不足困境,通过建设信息反馈平台,协调要素供给;优化发展环境,促进系统竞争协调;构建产业融合,促进优化升级. 相似文献
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Simulation for stochastic wind field is very important in analyzing dynamic responses of large complex structures due to strong
wind. The typical simulation method is the spectrum representation method (SRM), but the SRM has drawbacks of inferior precision
in lower frequency and slow calculating speed. In view of this, the modified Fourier spectrum method (MFSM) is introduced
into the simulation of stochastic wind field in this paper. In this method, phase information of wind velocity time history
is determined by cross power spectral density (CPSD) between adjacent points, and the wind velocity time history with time
and space correlation is generated by iterative modification for CPSD considering auto power spectral density (APSD). Simulation
of the wind field for a long-span bridge is undertaken to verify the effectiveness of the MFSM. Simulation results of the
SRM and the MFSM are compared. It can be concluded that the MFSM is more accurate and has higher calculation speed than the
SRM. 相似文献
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Wind loading is a dominant factor for design of a cable-membrane structure. Three orthogonal turbulent components, including the longitudinal, lateral and vertical wind velocities, should be taken into account for the wind loads. In this study, a stochastic 3D coupling wind field model is derived by the spectral representation theory. The coherence functions of the three orthogonal turbulent components are considered in this model. Then the model is applied to generate the three correlated wind turbulent components. After that, formulae are proposed to transform the velocities into wind loads, and to introduce the modified wind pressure force. Finally, a wind-induced time-history response analysis is conducted for a 3D cable-membrane structure. Analytical results indicate that responses induced by the proposed wind load model are 10%-25% larger than those by the con- ventional uncorrelated model, and that the responses are not quite influenced by the modified wind pressure force. Therefore, we concluded that, in the time-history response analysis, the coherences of the three orthogonal turbulent components are necessary for a 3D cable-membrane structure, but the modified wind pressure force can be ignored. 相似文献
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An integrated finite element model(FEM)of offshore wind tower-foundation-soil is established by ABAQUS, where a large-scale composite bucket foundation with seven compartments inside is applied to supporting the upper wind tower. The dynamic response of the structure-foundation system is studied under three seismic waves with the same peak ground acceleration of 0.035g. It can be seen that the dynamic response increases at the beginning with the structure height, then it decreases because the structural damping increases due to the mass effect of the upper wind turbine generator system. It is shown that the anti-liquefaction capacity of the soil inside and underneath the foundation is improved owing to the high overburden pressure of the upper structure and the constraint effect of the bucket skirt and subdivisions. Moreover, the liquefaction resistance of the soil inside the middle compartment is improved to a higher degree than that inside the side compartments. 相似文献
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讨论了一类带Poisson跳的随机微分方程解的存在唯一性问题,在局部Lipschitz条件下给出了带跳随机微分方程解的存在与唯一性的充分条件. 相似文献
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In this study on the nature of pressure signals generated by a deterministic or stochastic process in a bubbling fluidized
bed, pressure fluctuation measurements were carried out in a 300-mm-diamet column at 0.090 m and 0.40 m above the distributor
for different gas velocities. The method of detecting deterministic dynamic underlying pressure signals is proposed on the
basis of predictability of pressure fluctuations. The deterministic nature of dynamics in fluidizing system was verified.
The deterministic level of dynamics in fluidizing system was analyzed for different locations of pressure measurements and
different gas velocities.
Project supported by the Science and Engineering Foundation of SINOPEC, China (X599029) 相似文献
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在Lipschitz条件和线性增长条件下,利用压缩映像原理,获得了具有无穷时滞的随机泛函微分方程解局部存在唯一的充分条件。 相似文献
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赵彦玲 《十堰职业技术学院学报》2006,19(2):47-49
采用有限元方法,研究了轿车整车结构动力特性问题,分析了两种车速下微型轿车整车结构在随机路面载荷激励下的动态响应问题,为以后的结构动力改进提供参考依据。 相似文献
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In this paper, the effects of second-order difference-frequency wave forces on the global motion of an offshore wind turbine system with a large displacement under the survival condition are studied. In this case, the hydrodynamic force is the main force because the blades are feathered to reduce the lifting force. The first-order hydrodynamic forces are calculated by WADAM, while the second-order wave forces are calculated by a customized MATLAB module. Then the hydrodynamic coefficients are transferred to the wind turbine analytical code FAST. Through the comparisons of dynamic responses between the first- and second-order numerical models, it is found that the second-order wave forces significantly influence the motion of floating wind turbine under the survival condition. Moreover, neglecting the second-order force significantly underestimates the tension forces in the mooring lines. 相似文献