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冰激锥体振动物理模拟实验 总被引:3,自引:0,他引:3
应用DUT 1非冻结可破碎模型冰进行冰激锥体振动模拟实验的实验设备和模型的设计 ,给出了低冰速和高冰速两种情况下的结构位移曲线、冰力曲线及其幅值谱分析结果 ,得出了结构卓越频率和冰速与特征长度之比的关系 ,发现冰激锥体振动同冰激柱体振动一样有“频率锁定”现象。将实验结果与已有的冰排与圆柱相互作用实验结果进行比较 ,发现冰激锥体振动和冰激柱体振动有着相似的机理 相似文献
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孤立桩柱上冰压力的经验公式计算法及试验验证 总被引:10,自引:0,他引:10
本文简要介绍了冰排在桩柱前挤压破坏和压屈破坏的判别、冰排运动的驱动力,然后比较了各国常用的一些计算冰力的经验公式,推荐了公式,并推荐了公式中系数的取值法,最后通过冰力模拟试验,验证了所推荐公式和系数取值法的正确性。 相似文献
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海冰静力作用的特点及几种典型结构的冰力模型试验 总被引:7,自引:0,他引:7
海冰静力作用的重要特点是它对结构破坏程度的严重性以及对环境和结构条件的敏感性。冰力模型试验是流体模型试验,又是材料模型试验,所以要遵循特殊的模型律。本文介绍的几项冰力模型试验不仅证实了常被设计者忽略的直立桩柱前冰排的挤压破坏中常不同程度地包括有压屈破坏的成分,而且也证实了直立墙前冰排主要是压屈破坏,斜墙前冰排主要是弯曲破坏。同时给出了这些结构上冰力的量值。 相似文献
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对于浅海区采油平台等设施常采用斜坡式人工岛形式,虽然在一定程度上起到降低海冰对平台的作用,但是海冰沿着斜坡上爬至平台并形成堆积,同样也会对平台设施造成破坏,因此有必要对海冰堆积爬坡的关键参数进行研究。通过在冰排前进方向放置混凝土实体结构物模拟海冰堆积和爬坡过程,分析了模型冰爬坡和下滑角度、最大堆积高度等关键参数以及模型冰断裂长度的统计特性及其与变形模量的关系,试验结果表明水位越高,冰排越容易发生堆积爬坡。破碎的模型冰在结构物前堆积后,形成爬坡角和下滑角。爬坡角随着堆积体的增大而增大,下滑角则逐渐减小。堆积冰高度一定时,高度不再增加,在来冰方向会形成新的堆积。这种现象为浅海区海上结构物的防冰减灾提供了新思路。 相似文献
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基于测量结构水下光纤应变获取冰力的方法首次应用于渤海JZ20-2NW加锥导管架平台,该方法方便进行零点标定,可获取结构总冰力的绝对信息(包括均值和波动值)。首先介绍了JZ20-2NW平台的现场监测系统,主要包括结构水下应变响应记录冰力信息,甲板上部视频记录同步冰情(冰厚、冰速和来冰方向)信息和拾振器记录结构冰振响应;重点分析了由测点应变向结构总冰力的转化方法,并对总冰力进行了初步分析。将无量纲化实测冰力与5种典型冰力计算模型进行了比较,分析结果表明,锥体宽度与海冰厚度比值(简称"宽厚比")对冰力大小及变化起决定作用。 相似文献
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基于非线性有限元分析方法和LS-DYNA计算软件,使用黏聚单元法建立层冰的数值模型,并进行了层冰与锥形立柱相互作用的数值模拟,研究抗冰锥角、冰厚等参数对立柱所受冰载荷的影响。模拟结果与实测和试验结果吻合良好。研究结果表明:使用黏聚单元法建立的层冰模型可以较好地模拟出层冰的破碎和堆积过程,冰载荷计算结果与ISO冰力标准结果以及离散单元法计算结果吻合较好;锥形立柱的抗冰锥角大小对冰载荷影响明显,随着锥角增大,水平方向的最大冰力增大而竖直方向上最大冰力减小;锥形结构改变了碰撞过程中层冰的破坏形式;结构物所受冰力大小与层冰厚度呈正相关,且增加速度接近线性。 相似文献
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Designers and offshore operators frequently predict pack ice loading on offshore vessels by conducting scale model tests. One factor that can affect pack ice loading is the hull–ice friction coefficient. This research investigates the effect of hull–ice friction coefficients for a moored offshore vessel model and includes ice floe size and ice concentration as additional variables. A method of non-dimensional analysis is modified in order to deal with the multivariate nature of the new data. The resulting non-dimensional equation provides insight on relationships between the predicted pack ice force and the variables under investigation. The relationship between pack ice force and hull–ice friction coefficient is shown to be approximately a fourth root function, while the relationship for ice floe size, non-dimensionalised by the vessel beam, is approximately linear. The relationship between predicted pack ice force and ice concentration exists in a band bounded by cubic and sixth power curves. Applying the modified equation to the previous data sets shows the current analysis slightly improves the normalization of pack ice forces. 相似文献
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Wang Yonggang Shi Qingzeng
Postgraduate Tianjin University Tianjin Professor Dept. of Ocean Eng. Naval Arch. Tianjin Univ. Tianjin 《中国海洋工程》1996,(1)
The level ice thickness and compressive strength at the four measuring stations in the Liaodong Bay are inferred according to the hydrologic and meteorologic data there, then the yearly extreme ice forces on a solitary pile are calculated by the use of appropriate formula of ice forces and its probabilistic distribution is determined. Generally, the yearly extreme ice force follows Weibull distribution best as compared with Normal, Lognormal, and Extreme Value I distribution. On the other hand, the short-term distribution of ice forces on a solitary pile is obtained from the model experiment data analysis: It does not refuse Extreme Value I distribution. 相似文献
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A lot of tests on ice forces on vertical cylindrical piles are conducted in the ice basin of ice laboratory in Tianjin University to identify the characteristics of ice forces on fixed platforms in the Bohai Gulf. A function of ice forces is simplified on basis of test data, and the charateristics of the ice forces including the amplitude of the force and the breaking frequency of the ice sheet is detailed by use of the Fast-Fourier-Transform method. The results show that the ice breaking frequency presents a linear relationship with the ratio of ice moving velocity to ice thickness at low velocities. At high velocities, the frequency remains constant with the increase of the ratio of ice moving velocity to ice thickness. These conclusions are compared those published in literature. 相似文献
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The shielding effect of the front pile-row on the ice force acting on the hack pile-row is studied by ice force model tests. In the tests, the front pile-row is designed to model jacket legs and the hack pile-row to model the water resisting pipe-phalanx within the jacket. The shielding factor for ice force corresponding to different conditions are given in this paper. The research indicates that there are many factors, including the longitudinal and lateral spacing between the front and hack pile-row, ice attacking angle and the ratio of pile diameter to ice thickness, that influence the shielding effect on ice force. 相似文献
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作用于平台桩腿的海冰屈曲破坏冰压力随机过程模型及其参数确定 总被引:2,自引:1,他引:2
冰对结构的作用过程是典型的随机过程。本文在冰压力过程为平稳过程的假设下,从渤海海冰对平台桩腿作用的大量实测冰压力数据中,选取了21条冰屈曲破坏时的冰压力时程曲线,对它们进行谱分析后,得到了单点冰屈曲破坏的压力随机过程的谱密度,并确定了谱参数及其跟环境要素的关系,依据文献[1]中冰压力沿圆柱面的空间分布,建立了绕桩腿的冰压力随机场模型,并得到了作用于桩腿的总冰力随机过程及其谱密度。本文的研究成果为平台结构冰激随机振动和疲劳累积损伤分析提供了荷载基础 相似文献
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冰脊间遮掩作用对冰?水拖曳力影响的实验研究 总被引:1,自引:1,他引:0
为定量研究多冰脊之间的尾流遮掩作用对海冰漂移运动的影响,物理模型试验(试验有限水深为0.45 m)测量了多冰脊拖曳力的衰减变化。冰脊模型选用底角为45°的等腰直角三角形,选取了4种入水深度、9种冰脊间距进行测量。试验得到了前后冰脊拖曳力及其比值在尾流遮掩情况下的变化规律。前冰脊拖曳力与单冰脊情况一致,与冰脊速度的平方保持线性关系;而后冰脊在间距较小时出现了反向拖曳力,随冰脊间距的增大,后冰脊拖曳系数先减小再增大至不变。前后冰脊拖曳力比值的变化规律可以用指数遮掩函数来描述,该遮掩函数与冰脊间距和入水深度有关而与流速无关。通过与现有海冰模式中的遮掩函数对比,研究结论增强了该指数公式的适用性,加强了对海冰动力学模式中遮掩函数的理解。 相似文献
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A New Model for Ice Forces on A Conical Structure 总被引:1,自引:0,他引:1
The ice force is an important factor to be taken into account for offshore structures in cold regions, and the calculation method of the ice force is meaningful for the offshore structure design. The cone is now used as an optimal ice-resistant structure because it can cause bending failure of the ice sheet. The interaction between an ice sheet and a conical structure is studied in this paper and Croasdale‘s model is modified based on field observations. The newly built model separates the ice sheet into the emersed part and the floating part, and the equilibrium analyses are canied out respectively. The bending moment distribution of the ice sheet is analyzed for the determination of the position of bending failure, which serves as a supplementary restraint. The analytic solution of the ice foree on a conical structure is obtained it is verified with the experimental data of previous researches. 相似文献
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海洋平台结构的冰力作用模型 总被引:10,自引:0,他引:10
首先分析了工程中静冰力计算中普遍应用的Korzhavin -Afanasev公式和Schawz公式 ,提出了统一的静冰力模型 ,给出了挤压破坏、屈曲破坏和弯曲破坏冰力系数函数CI(t)。应用该冰力模型分析了自激振动产生的条件 ,指出冰屈曲破坏和弯曲破坏动冰力可以作为强迫振动模型 ,冰挤压破坏动冰力则需要考虑CI(t)与冰阻尼的耦合效应。最后应用冰力一般模型计算单自由度结构的响应 相似文献
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基于黏聚单元法的抗冰海洋平台与层冰相互作用数值模拟 总被引:1,自引:1,他引:0
通过商业有限元软件LS-DYNA采用黏聚单元法模拟层冰的断裂问题,在IIHR冰池模型试验相同缩尺比参数下对KULLUK抗冰平台受到的冰力进行数值计算,探究冰厚与冰速等冰况参数对平台冰力的影响。计算结果表明,在极地作业平台主要遭遇北极海域冰况范围下,相同冰厚情况时冰速变化对倒锥形结构平台的横向冰力影响不大,而同冰速时冰力随着冰厚的增加接近线性增加。同时将计算所得结果与同条件下IIHR冰池模型试验数据、ARCTEC、ACL非冻结模型冰试验数据、实船数据和通过ISO19906规范中提供的针对大锥面结构受到层冰冰力的经验公式计算所得数据等进行了对比,验证了选用冰参数的可靠性以及该数值模型在模拟大尺度宽锥形平台遭受层冰作用问题中的适用性。 相似文献