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The statistical characteristics and parameters of loads and resistances are systematically studied for the development of probabilistic limit state design method for steel jacket offshore platforms in the China offshore area. The mean value, standard variance and distribution pattern of resistances and loads in different base perieds are presented. The statistical parameters of structural member resistance, self-weight, deck live load, and environmental loads such as wind, wave, current and ice, which are drawn on a large amount of observatian data of offshore environmental factors, and the design data of platforms in China Bohai Sea form the data set, providing a necessary basis for the calibration of load and resistance factors to realize the reliability-based design of jacket platform structures.
Analyzed in this paper are the influencing factors,characteristics,and mechanism of land-sea interaction for the Taihu Lake Basin.The course of mass movement and energy transformation between land and sea in the Taihu Lake Basin has experienced three different stages,namely,ocean predominance,balance between land and sea,and land predomi-nance.In the paper the process of the formation and the evolution of the Taihu Lake is studied considering the land-sea interaction.
It is assumed that,during the design period,the waves acting on breakwaters are divided into three types:standing wave,broken wave and breaking wave,and the wave heights fit the Rayleigh distribution while the water depths,wave periods and duration of breaking wave impact force fit normal distribution.Based on the random samples of water depths,wave heights,wave periods and duration of breakingwave impact force,the types ofwaves acting on breakwaters are dis-tinguished and the time-history model of the wave force is determined.The motions of caisson breakwaters under the wave force are simulated by a dynamic numerical model and the statistic characteristics of the dynamic responses are analyzed with the Monte Carlo method.A probabilistic procedure to analyze the motion of the breakwater is developed therein.The procedure is illustrated by an example.
For the maintenance of the pipelines which pipe oil from oil fields in the Bohai Gulf of China,an underwater vehicle for pipeline detection and maintenance(PDM-UV)is designed.In this paper,the maneuverability and motion simulation of PDM-UV are studied.A general dynamic equation to describe the hydrodynamics of PDM-UV is presented.For a deep understanding of the dynamics of PDM-UV,which is somewhat different from normal underwater vehicles in configura-tion,the maneuverability is discussed in terms of hydrodynamic coefficients with experimental results.Finally,the whole motion simulation system is introduced and simulation results are presented to demonstrate the feasibility and correctness of the simulation platform.
Optical fiber sensors have received increasing attention in the fields of aeronautic and civil engineering for their su-perior ability to stand explosion,immunity to electromagnetic interference and high accuracy,especially fit for measure-ment applications in harsh environment.In this study,a novel FBG(fiber Bragg grating)strain sensor,which is pack-aged in a1.2mm stainless steel tube with epoxy resin,is developed.Experiments are conducted on the universal materi-al testing machine to calibrate its strain transferring characteristics.The sensor has the advantages of small size,high pre-cision and flexible use,and exhibits promising potentials.Five tube-packaged strain FBG sensors have been applied to the vibration experiment of a submarine pipeline model.The strain measured with the FBG sensor agrees well with that measured with the electric resistance strain sensor.
The interaction between waves,currents and bottoms in estuarine and coastal regions is ubiquitious,in particular the dynamic mechanism ofwaves on large-scale slowly varying currents.The wave action concept may be extended and appli-cated to the study of the mechanism.Considering the effects of moving bottoms and starting from the Navier-Stokes equa-tion of motion of a viscous fluid including the Coriolis force,a generalized mean-flow model theory for the nearshore re-gion,that is,a set of mean-flow equations and their generalized wave action equation involving the three newkinds of ac-tions termed respectively as the currentwave action,the bottomwave action and the dissipative wave action which can be applied to arbitrary depth over moving bottoms and ambient currents with a typical vertical structure,is developed by ver-tical integration and time-averaging over a wave period,thus extending the classical concept,wave action,from the ideal averaged flow conservative system to the real averaged flow dissipative dynamical system,and having a large range of ap-plication.
Unlike most previous studies on vortex-induced vibrations of a cylinder far from a boundary,this paper focuses on the influences of close proximity of a submarine pipeline to a rigid seabed boundary upon the dynamic responses of the pipeline in ocean currents.The effects of gap-to-diameter ratio and those of the stability parameter on the amplitude and frequency responses of a pipeline are investigated experimentallywith a novel hydro-elastic facility.A comparison is made between the present experimental results of the amplitude and frequency responses for the pipes with seabed boundary ef-fects and those for wall-free cylinders given by Govardhan and Williamson(2000)and Anand(1985).The comparison shows that the close proximity of a pipeline to seabed has much influence on the vortex-induced vibrations of the pipeline.Both the width of the lock-in ranges in terms of V r and the dimensionless amplitude ratio A max /D become larger with the decrease of the gap-to-diameter ratio e/D.Moreover,the vibration of the pipeline becomes easier to occur and its ampli-tude response becomes more intensive with the decrease of the stability parameter,while the pipeline frequency responses are affected slightly by the stability parameter.
This paper is mainly concerned with the turbulence in oscillatory bottom boundary layers over flat or rippled seabeds.Owing to the strong shear and anisotropy of oscillatory flow,an anisotropic turbulence mathematical model is set up using the finite difference method,and the computational results of the model are verified by comparisons with well-known experiments.Turbulent energy,dissipation and Reynolds stress can all be computed with this mathematical mod-el,and the development processes of a large coherent vortex structure over a rippled bed,such as main flow separation,coherent vortex formation and curling,coherent vortex ejection and breaking up,are successfully simulated.
This study is devoted to the interaction between water surface waves and a thin layer of viscoelastic mud on the bot-tom.On the assumption that the mud layer is comparable in thickness with the wave boundary layer and is much smaller than the wavelength,a two-layer Stokes boundary layer model is adopted to determine the mud motions under the waves.Analytical expressions are derived for the near-bottomwater and mud velocity fields,surface wave-damping rate,and in-terface wave amplitude and phase lag.Examined in particular is how these kinematic quantities may depend on the vis-cous and elastic properties of the mud.
ScholarOne Manuscripts Log In
- Volume 34
- Issue 3
- June 2020
- Superintended by:
CHINA ASSOCIATION FOR SCIENCE AND TECHNOLOGY
- Sponsored by:
Chinese Ocean Engineering Society （COES）
- Edited by:
Nanjing Hydraulic Research Institute
Adaptive Predictive Inverse Control of Offshore Jacket Platform Based on Rough Neural Network
Numerical Simulation of Water Exchange Characteristics of the Jiaozhou Bay Based on A Three-Dimensional Lagrangian Model
A Global Reliability Assessment Method on Aging Offshore Platforms with Corrosion and Cracks