Experimental Investigation of Wave Loads on Ice Masses at Different Proximity to Fixed Offshore Structure

2016 ◽  
Author(s):  
Tanvir Sayeed ◽  
Bruce Colbourne ◽  
David Molyneux ◽  
Ayhan Akinturk
Keyword(s):  
Experimental Investigation ◽  
Wave Loads ◽  
Offshore Structure

Effect of Seabed Slope on Offshore Pile Lateral Behaviour Under Wave Force

2010 ◽  
Author(s):  
Sathyanarayanan Dhandapani ◽  
Muthukkumaran Kasinathan
Keyword(s):  
Finite Element ◽  
Vertical Direction ◽  
Pile Group ◽  
Element Model ◽  
Wave Force ◽  
Wave Forces ◽  
Extreme Conditions ◽  
Offshore Platforms ◽  
Wave Loads ◽  
Offshore Structure

Fixed offshore platforms supported by pile foundations are required to resist dynamic lateral loading due to wave forces. The response of a jacket offshore tower is affected by the flexibility and nonlinear behavior of the supporting piles. In this study, a typical fixed offshore platform is chosen, and dynamic wave analysis is performed on it. Analysis has been performed for normal environmental conditions and extreme conditions. For the foundation, the deflections and reactions at regular intervals along the vertical direction from the seabed have been found out from the dynamic analysis, and the results have been compared for normal and extreme conditions. The aim of this study is to investigate the effects of the combined lateral and vertical loads on pile group foundation of a fixed offshore structure and the effects of seabed slope on the pile responses. To provide a more accurate and effective design for offshore pile foundation systems under axial structural loads and lateral wave loads, a finite element model which is modelled in FLAC3D is employed herein to determine the soil structure interaction under similar loading conditions. Three dimensional modelling and the analyses are done using FLAC3D — a finite element package.

The Effect of Wave Directionality on Low Frequency Motions and Mooring Forces

2009 ◽  
Author(s):  
Olaf J. Waals
Keyword(s):  
Water Depth ◽  
Transfer Functions ◽  
Low Frequency ◽  
Sensitivity Study ◽  
Wave Loads ◽  
Offshore Structure ◽  
Frequency Wave ◽  
Drift Theory ◽  
Mooring Forces ◽  
Drift Forces

Operability of offshore moored ships can be affected by low frequency wave loads. The low frequency motions of a moored ship may limit the uptime of an offshore structure such as an LNG offloading terminal. The wave loads that cause the main excitation of these low frequency motions are usually computed using second order wave drift theory for long crested waves, which assumes that the low frequency components are only related to waves coming from the same direction. In this method short crested seas are dealt with as a summation of long crested seas, but no interaction between the wave components traveling in different directions is usually taken into account. This paper describes the results of a study to the effect of 2nd order low frequency wave loads in directional seas. For this study the drift forces related to the interaction between waves coming from different directions is also included. This is done by computing the quadratic transfer functions (QTF) for all possible combinations of wave components (frequencies and directions). Time traces of drift forces are generated and compared to the results without wave directional interaction after which the motions of an LNG carrier are simulated. A sensitivity study is carried out towards the number of direction steps and the water depth. Finally the motions of an LNG carrier in shallow water (15m water depth) are simulated and mooring forces are compared for various amounts of wave spreading.

Numerical Simulation of Rogue Waves Based on the Fourth-Order NLS Equation for Laboratory Experimental Investigation

2010 ◽  
Author(s):  
Hanhong Hu ◽  
Ning Ma ◽  
Xuefeng Wang ◽  
Xiechong Gu
Keyword(s):  
Experimental Investigation ◽  
Fourth Order ◽  
Rogue Waves ◽  
Structure Design ◽  
Domain Model ◽  
Random Wave ◽  
Offshore Structure ◽  
Nls Equation ◽  
Transient Wave ◽  
Wave Trains

The main purposes of investigating the generation of the rogue waves in offshore engineering include: 1) prediction of its occurrence to protect the offshore structure from attacking; 2) the experimental investigation of rogue waves/structure interaction for the structure design. The latter one calls high requirement of wave generation and calculation. In this paper, we establish a spatial domain model of fourth order nonlinear Schro¨dinger (NLS) equation for describing deep-water wave trains in moving coordinate system. For the first purpose mentioned above, this paper presents the evolution of random wave trains in real sea state described by the Joint North Sea Wave Project (JONSWAP) power spectrum numerically, which is governed by the NLS equation. The parameters of the spectrum are evaluated to discuss their effect on the occurrence of rogue waves. For the second purpose to generate rogue waves in experimental tank efficiently, the transient wave is focused for its allowance of precise determination of concentration place/time. First we simulate the three-dimensional transient waves in the numerical tank modeling the deepwater basin with double-side multi-segmented wave-maker in Shanghai Jiao Tong University (SJTU) with linear superposing theory. To discuss its nonlinearity for the guidance of experiment, the transient wave is set as the initial condition of the NLS equation and the difference from the linear simulation is presented, which could be given as the suggestion to the preparation of experiment.

Engineering Establishment of Living Quarters for Jack-Up Rig Structures

2016 ◽  
Author(s):  
Yeong Su Ha ◽  
Joo Shin Park ◽  
Jeong Bon Koo ◽  
Byung Jin Cho ◽  
Kuk Yeol Ma ◽  
...  
Keyword(s):  
Structural Engineering ◽  
Three Dimensional ◽  
Technical Specification ◽  
International Standards ◽  
Structural Safety ◽  
Fe Model ◽  
Wave Loads ◽  
Offshore Structure ◽  
Local Loads ◽  
Jack Up

The Living-Quarters (hereafter referred to as ‘LQ’) is one of the major structures for ship and offshore structure. The LQ gives safe living conditions to crews on board. Until now the structural design of LQ structure is based on simplistic beam calculation to determine the initial scantling under design load. These days, safety for people is a raising issue. It is needed to meet the high oil company’s needs as well as technical specification throughout offshore project. But, the engineering procedure for LQ structure is not clearly defined by classification of society rules and international standards. In this paper, the newly engineering procedure for LQ design is established considering LQ global loads with local loads for large equipment such as helideck structure, telecom mast and life saving appliances, and so on. To consider LQ global loads with local loads, the integrated three dimensional FE model and high technology engineering should be needed to require many kind of rules for equipment. Recently, the damage of LQ structure is occasionally reported during towing condition for jack-up rig structure. The LQ of jack-up rig is encountered such as slamming pressure and greenwater produced by harsh wave loads during towing condition because of small height of freeboard comparing to the wave height. To verify the structural safety under towing condition, the detailed non-liner analysis is performed to verify the load-carrying capacity against greenwater pressure. We newly propose a structural engineering procedure to improve the reliability of the LQ design in the jack-up rigs. From basis of this procedure, a more reasonable and optimized results are proposed as a practical manner as well as scientific approach.

URANS Predictions of Low-Frequency Damping of a LNGC

2019 ◽  
Author(s):  
Frédérick Jaouën ◽  
Arjen Koop ◽  
Lucas Vatinel
Keyword(s):  
Low Frequency ◽  
Offshore Structures ◽  
Viscous Damping ◽  
Wave Loads ◽  
Viscous Effects ◽  
Offshore Structure ◽  
Time Step ◽  
Cfd Simulations ◽  
Damping Coefficients ◽  
Hydrodynamic Damping

Abstract The horizontal motions of a moored offshore structure in waves are dominated by the resonance phenomena that occur at the natural frequencies of the system. Therefore, the maximum excursions of the structure depend on both the wave loads and the damping in the system. At present, potential flow calculations are employed for predicting the wave loads on offshore structures. However, such methods cannot predict hydrodynamic damping which is dominated by viscous effects. Therefore, the current practice in the industry is to obtain the low-frequency damping based on model testing. Nowadays, CFD simulations also have the potential to predict the low-frequency viscous damping of offshore structures in calm water. To obtain confidence in the accuracy of CFD simulations, a proper validation of the results of such CFD calculations is essential. In this paper, the flow around a forced surging or swaying LNGC is calculated using the CFD code ReFRESCO. The objective is to assess the accuracy and applicability of CFD for predicting the low-frequency viscous damping. After a description of the code and the used numerical methods, the results are presented and compared with results from model tests. Both inertia and damping coefficients are analyzed from the calculated hydrodynamics loads. Extensive numerical studies have been carried out to determine the influence of grid resolution, time step and iterative convergence on the flow solution and on the calculated damping. The numerical uncertainty of the results are assessed for one combination of amplitude and period for the surge motion. The CFD results are compared to experimental results indicating that the calculated damping coefficients agree within 5% for both surge and sway motion.

Experimental investigation on a freestanding bridge tower under wind and wave loads

2016 ◽  
Vol 57 (5) ◽  
pp. 951-968 ◽  
Author(s):  
Xiaodong Bai ◽  
Anxin Guo ◽  
Hao Liu ◽  
Wenli Chen ◽  
Gao Liu ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Wave Loads ◽  
Bridge Tower

scholarly journals Comparative analysis of tripod offshore structure

2020 ◽  
Vol 72 (11) ◽  
pp. 1021-1030
Keyword(s):  
Comparative Analysis ◽  
Finite Elements ◽  
Velocity Profile ◽  
Wave Forces ◽  
Wave Loads ◽  
Analysis Program ◽  
Offshore Structure ◽  
Marine Structures ◽  
Finite Elements Analysis ◽  
Structural Parts

Marine structures are nowadays used in a variety of ways. The analysis of a tripod-type offshore structure sixty m in total height is performed in this study. In addition to operation-related loads, the structure is also under the effect of wind and wave loads. While the Eurocode velocity profile is used to calculate wind forces, the Airy wave velocity profile is utilized to determine wave forces. The model is created by a finite elements analysis program, and is composed of fluid and structural parts. The interaction of the parts is ensured by Coupled Eulerian Lagrangian (CEL) technique.

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