Effect of Cyclic Loading Frequency on Undrained Behaviors of Undisturbed Marine Clay   总被引：2，自引：0，他引：2  

陈云敏  姬美秀黄博 《中国海洋工程》2004,18(4):643-651

Based on a series of cyclic triaxial tests, the effect of cyclic frequency on the undrained behaviors of undisturbed marine clay is investigated. For a given dynamic stress ratio, the accumulated pore water pressure and dynamic strain increase with the number of cycles. There exists a threshold value for beth the accumulated pore water pressure and dynamic strain, below which the effect of cyclic frequency is very small, but above which the accumulated pore water pressure and dynamic strain increase intensely with the decrease of cyclic frequency for a given number of cycles. The dynamic strength increases with the increase of cyclic frequency, whereas the effect of cyclic frequency on it gradually diminishes to zero when the number of cycles is large enough, and the dynamic strengths at different frequencies tend to the same limiting minimum dynamic strength. The test results demonstrate that the reasons for the frequency effect on the undrained soil behaviors are beth the creep effect induced by the loading rate and the decrease of sample effective confining pressure caused by the accumulated pore water pressure.  相似文献   

钢筋混凝土梁结构断裂损伤诊断方法     

周尚志  王丽华刘瑛 《海洋工程》2005,23(4):47-51

提出一种基于BP神经网络的结构破损诊断方法,该方法以结构破损前后柔度的变化作为破损诊断网络输入,为了解决由于系统响应样本数据空间分布不均匀对网络收敛速度及网络诊断影响问题,对网络训练样本采用广义空间格点进行了交换,模拟算例及应用实例均表明,本文方法能准确诊断结构破损位置与破坏程度,是一种有效的结构破损诊断方法.  相似文献   

A New Pursuit Mode of Nonlinear Wave Surface     

孙大鹏李玉成  郭海滨 《中国海洋工程》2004,18(2):257-266

The numerical mode of nonlinear wave transformation based on both the Laplace equation for water field and the Bemoulli equation for water surface is a kind of time-domain boundary problem with initial conditions. And the basis for establishing the numerical mode of nonlinear wave in time domain is to trace the position of wave free surface and to calculale the instantaneous surface height and surface potential function. This paper firstly utilizes the ‘0-1‘ combined BEM to separate the boundary by means of discretization of Green‘ s integral equation based on the Laplace equation, then separates the free surface of wave with FEM and derives the FEM equation of wave surface that satisfies the nonlinear boundary conditions. By jointly solving the above BEM and FEM equations, the wave potential and surface height could be obtained with iteration in time domain. Thus a new kind of nonlinear numerical mode is established for calculating wave transformation. The wave test in the numerical wave tank shows that the numerical simulation with this mode is of high accuracy.  相似文献   

Numerical Simulation of Dynamic Response of Supple Nets     

朱立新梁振林  黄六一赵芬芳 《中国海洋工程》2006,20(3):443-456

1 .Introduction Owing to the decline of capture fisheries andsaturation of traditional inshorefarms ,sea cage cul-ture as a newtype of aquaculture is developingrapidlyin China .However ,cage culture is a highriskoperation.The practice is vulnerable to natural hazards ,such as strong tides ,storms and typhoons .So,it is necessaryto assess the behavior of a sea cage exposedto waves and current before the designandinstallation of the structure . Computer simulation,due to its many advantages ,ha…  相似文献   

Drag Coefficient,Dynamic Roughness and Reference Wind Speed     

Paul?A.?HwangEmail author 《Journal of Oceanography》2005,61(3):399-413

Surface waves are the roughness element of the ocean surface. The parameterization of the drag coefficient of the ocean surface is simplified by referencing to wind speed at an elevation proportional to the characteristic wavelength. The dynamic roughness is analytically related to the drag coefficient. Under the assumption of fetch limited wave growth condition, various empirical functions of the dynamic roughness can be converted to equivalent expressions for comparison. For datasets covering a wide range of the dimensionless frequency (inverse wave age), it is important to account for the variable rate of wave development at different wave ages. As a result, the dependence of the Charnock parameter on wave age is nonmonotonic. Finally, the analysis presented here suggests that the significant wave steepness is a sensitive property of the ocean surface and a single variable normalization of the dynamic roughness using a wavelength or wave height parameter actually produces more robust functions than bi-variable normalizations using wave height and wave slope.  相似文献   

Simulations of Annual Cycle of Phytoplankton Production and the Utilization of Nitrogen in the Yellow Sea     

Tian?TianEmail author  Hao?Wei  Jian?Su  Changsoo?Chung 《Journal of Oceanography》2005,61(2):343-357

A nutrient dynamic model coupled with a 3D physical model has been developed to study the annual cycle of phytoplankton production in the Yellow Sea. The biological model involves interactions between inorganic nitrogen (nitrate and ammonium), phosphate and phytoplankton biomass. The model successfully reproduces the main features of phytoplankton-nutrient variation and dynamics of production. 1. The well-mixed coastal water is characterized by high primary production, as well as high new production. 2. In summer, the convergence of tidal front is an important hydrodynamic process, which contributes to high biomass at frontal areas. 3. The evolution of phytoplankton blooms and thermocline in the central region demonstrate that mixing is a dominant factor to the production in the Yellow Sea. In this simulation, nitrate- and ammonium-based productions are estimated regionally and temporally. The northern Yellow Sea is one of the highly ranked regions in the Yellow Sea for the capability of fixing carbon and nitrogen. The annual averaged f-ratio of 0.37 indicates that regenerated production prevails over the Yellow Sea. The result also shows that phosphate is the major nutrient, limiting phytoplankton growth throughout the year and it can be an indicator to predict the bloom magnitude. Finally, the relative roles of external nutrient sources have been evaluated, and benthic fluxes might play a significant role in compensating 54.6% of new nitrogen for new production consumption.  相似文献   

Ekman螺线的动力学结构     

纪文君  王卫强 《台湾海峡》2002,21(3):340-343

介绍了Ekman螺线的动力学结构 ,分析研究了风应力及海水内部的动量传递形式 .结果表明 :动量传递方向与海流方向成 45°左偏 .这对于研究海洋内部的动力结构是有意义的 .  相似文献   

Dynamic Analysis of a Single-Column Platform (II)     

Lian Gan  Ni Kan  Hu Kai Guo Dawei . Professor  Senior Engineer  Marine Design & Research Institute of China  Shanghai . Senior Engineer  Marine Design & REsearch Institute of China  Shanghai . Engineer  Marine Design & Research Institute of China  Shanghai 《中国海洋工程》1992,(4)

This paper describes the study of a single-column structure used as well-head platform. In order to check the reliability of computation theory and programme, model tests have been carried out. The paper introduces the conclusion of tests and the dynamic properties of single-column platform are obtained.  相似文献   

不同软基处理方法适用性比较   总被引：8，自引：0，他引：8  

熊丛博  于定勇 《海岸工程》2003,22(1):20-26

总结分析了国内外现有的软土地基处理的各种方法。通过对采用不同方法进行软基处理的工程实例处理效果的定量对比，发现不同软基处理方法的适用性差异很大，多数工程中仅用一种方法很难达到设计要求，而两种或多种方法联合则可望取得更好的效果。  相似文献   

动荷载作用下海底粉土的孔压响应及其动强度   总被引：5，自引：0，他引：5  

冯秀丽  叶银灿  马艳霞  林霖 《中国海洋大学学报(自然科学版)》2002,32(3):429-433

本文选用近海分布较广的粉土为研究对象 ,利用室内动三轴试验结果 ,找出动荷载作用下粉土的动应力应变关系 ,分析模拟波浪荷载作用下粉土中的孔压响应、临界循环次数 ,确定波浪作用下粉土的应力状态、破坏临界循环次数 ,判断不同深度处的粉土发生液化的可能性及发生液化所需要的时间 ;研究粉土在动荷载作用下的强度降低 ,为海上工程设计和施工提供科学依据。  相似文献