非线性波浪作用下单桩动力响应分析

发布时间：2018-04-15 04:20

本文选题：线性波 + Stokes波　；参考：《重庆交通大学》2016年硕士论文

【摘要】：随着海洋工程的不断发展,单桩结构以其“工艺简单、适用性强、造价合理”等各种优点已被广泛的应用于海上风机、潮汐发电、船舶靠泊以及浮式结构物的锚固等各类港口及海岸工程中。对于海中的孤立桩柱结构,波浪是一类重要的动力因素,往往会在桩柱构件上产生较大的内力及位移,因此,研究波浪对桩柱的动力作用具有重要的意义。本文针对单自由度的孤立桩柱系统,分别应用线性波理论、二阶、三阶及五阶Stokes波理论对五种工况进行了动力分析谱运算,分析了波高、周期、水深、潮流及海浪谱的变化对波浪动力谱运算产生的影响,并对比了不同波浪理论结果之间的差异性随上述因素变化的规律,得出主要内容及结论如下:(1)波高、周期、水深的变化均对动力谱计算产生较大影响,其中波高变化引起的谱均方值变幅最大,周期次之,最后是水深。当周期和水深变化时,尽管荷载谱均方值未见明显放大,但由于外部荷载中心频率和振动固有频率发生了变化进而导致频率响应函数改变,因此亦产生较大的响应。二阶、三阶、五阶波理论与线性波理论间结果的差异性随波高、周期、水深的变化始终满足:二阶波理论与线性波理论之间略有差异性但不明显,三阶波与线性波理论之间差异最大,五阶波的结果始终处于二阶和三阶结果之间,且不同波浪理论的计算结果在波高较大、周期相对较小及水深较深时有较大差异性,明显此时继续用线性波代替非线性波进行工程计算不合理。(2)当桩径变化时,外部波浪荷载和桩柱本身的固有属性均随桩径的改变而改变,响应均方值在桩径的合理变化范围内往往会出现一段最优区间,在该区间内,响应均方值变化平稳且值相对较小。潮流主要影响荷载中的波阻力及阻力矩,在流速相对较大时对阻力荷载有明显的放大。同时,不同的海浪谱的选取亦会对谱动力计算产生较大影响,实际工程中应结合地域特性和外部条件合理选择计算用的海浪谱具体形式。因此,在工程设计中应综合考虑以上各种影响因素,根据设计条件合理的选用适当的波浪理论来进行工程计算,在不同波浪理论计算结果差异较大段,基于五阶波理论的动力计算结果往往既能提高精度又不至于使计算结果偏大过于保守或偏小而提高风险,该种情况建议选择五阶波理论计算。
[Abstract]:With the continuous development of marine engineering, single pile structure has been widely used in offshore fan and tidal power generation because of its advantages of "simple technology, strong applicability, reasonable cost" and so on.Ship berthing and floating structure Anchorage and other port and coastal engineering.For isolated pile-column structures in the sea, wave is a kind of important dynamic factor, which often produces large internal forces and displacements on pile-column members. Therefore, it is of great significance to study the dynamic effect of waves on pile-column.In this paper, the linear wave theory, the second order, the third order and the fifth order Stokes wave theory are used to calculate the dynamic spectrum of the isolated pile-column system with single degree of freedom, and the wave height, period and water depth are analyzed.The influence of the variation of tidal current and wave spectrum on the wave dynamic spectrum operation is compared, and the law of the difference between the different wave theory results with the above factors is compared. The main contents and conclusions are as follows: 1) wave height and period.The variation of water depth has a great influence on the calculation of dynamic spectrum. The variation of spectral mean square caused by the variation of wave height is the largest, followed by the period, and finally the water depth.When the period and water depth change, although the mean square value of load spectrum is not enlarged obviously, the frequency response function is changed due to the change of external load center frequency and vibration natural frequency.The difference between the second-order, third-order and fifth-order wave theory and the linear wave theory is always satisfied with the variation of wave height, period and water depth: the difference between the second-order wave theory and the linear wave theory is slight but not obvious.The difference between the theory of third-order wave and linear wave is greatest, the result of five-order wave is always between second-order and third-order, and the results of different wave theory are quite different when the wave height is large, the period is relatively small and the water depth is deeper.It is obvious that the linear wave is used instead of the nonlinear wave to carry out the engineering calculation. 2) when the diameter of the pile changes, the external wave load and the inherent properties of the pile itself both change with the change of the diameter of the pile.In the range of reasonable variation of pile diameter, the response mean square value often appears an optimal interval, in which the response mean square value changes steadily and the value is relatively small.The tidal current mainly affects the wave resistance and the resistance moment in the load, and when the velocity is relatively large, the resistance load is obviously enlarged.At the same time, the selection of different wave spectrum will also have a great impact on the spectrum dynamic calculation. In practical engineering, the specific form of wave spectrum should be reasonably selected according to the regional characteristics and external conditions.Therefore, the above factors should be considered comprehensively in the engineering design. According to the design conditions, the appropriate wave theory should be selected to carry out the engineering calculation.The dynamic calculation results based on the fifth order wave theory can not only improve the accuracy but also not cause the calculation results to be too conservative or small to raise the risk. In this case, it is suggested that the fifth order wave theory be chosen for calculation.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P75;TV139.2

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