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.

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.

A SPLINES BASED METHOD FOR MODELING THE HUMAN HEAD FOR USE IN FINITE ELEMENTS ANALYSIS

2017 ◽  
Author(s):  
Daniel Ponce ◽  
Eduardo Szpoganicz ◽  
Leonardo Mejia Rincon ◽  
Ernesto Ponce Lopez
Keyword(s):  
Finite Elements ◽  
Human Head ◽  
Finite Elements Analysis

scholarly journals Determination of Force Coefficients for a Submerged Rigid Breakwater under the Action of Solitary Waves

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 315
Author(s):  
Francesco Aristodemo ◽  
Giuseppe Tripepi ◽  
Luana Gurnari ◽  
Pasquale Filianoti
Keyword(s):  
Solitary Waves ◽  
Pressure Sensors ◽  
Wave Forces ◽  
Wave Loads ◽  
Force Coefficients ◽  
Wave Flume ◽  
Physical Tests ◽  
The Difference ◽  
The University ◽  
Semi Empirical

We present an analysis related to the evaluation of Morison and transverse force coefficients in the case of a submerged square barrier subject to the action of solitary waves. To this purpose, two-dimensional experimental research was undertaken in the wave flume of the University of Calabria, in which a rigid square barrier was provided by a discrete battery of pressure sensors to determine the horizontal and vertical hydrodynamic forces. A total set of 18 laboratory tests was carried out by varying the motion law of a piston-type paddle. Owing to the low Keulegan–Carpenter numbers of the tests, the force regime of the physical tests was defined by the dominance of the inertia loads in the horizontal direction and of the lift loads in the vertical one. Through the use of the time series of wave forces and the undisturbed kinematics, drag, horizontal inertia, lift, and vertical inertia coefficients in the Morison and transverse semi-empirical schemes were calculated using time-domain approaches, adopting the WLS1 method for the minimization of the difference between the maximum forces and the linked phase shifts by comparing laboratory and calculated wave loads. Practical equations to calculate these coefficients as a function of the wave non-linearity were introduced. The obtained results highlighted the prevalence of the horizontal forces in comparison with the vertical ones which, however, prove to be fundamental for stability purposes of the barrier. An overall good agreement between the experimental forces and those calculated by the calibrated semi-empirical schemes was found, particularly for the positive horizontal and vertical loads. The analysis of the hydrodynamic coefficients showed a decreasing trend for the drag, horizontal inertia, and lift coefficients as a function of the wave non-linearity, while the vertical inertia coefficient underlined an initial increasing trend and a successive slight decreasing trend.

An Evolutionary Multi-Objective Optimization Approach to the Topology Optimization of Auxetic Structures

2002 ◽  
Author(s):  
Ashraf O. Nassef
Keyword(s):  
Topology Optimization ◽  
Elastic Modulus ◽  
Finite Elements ◽  
Multiobjective Optimization ◽  
Poisson Ratio ◽  
Optimization Approach ◽  
Multi Objective Optimization ◽  
Finite Elements Analysis ◽  
Multi Objective ◽  
Auxetic Structures

Auxetic structures are ones, which exhibit an in-plane negative Poisson ratio behavior. Such structures can be obtained by specially designed honeycombs or by specially designed composites. The design of such honeycombs and composites has been tackled using a combination of optimization and finite elements analysis. Since, there is a tradeoff between the Poisson ratio of such structures and their elastic modulus, it might not be possible to attain a desired value for both properties simultaneously. The presented work approaches the problem using evolutionary multiobjective optimization to produce several designs rather than one. The algorithm provides the designs that lie on the tradeoff frontier between both properties.

Wave Forces on Cylindrical Members at Offshore Structure

1991 ◽  
Author(s):  
Yuzo Mizuno ◽  
Kazuo Tokikawa ◽  
Mitsunari Hirasawa ◽  
Yutaka Nagai ◽  
Takashi Kadono
Keyword(s):  
Wave Forces ◽  
Offshore Structure

Seismic Analysis of a Double-Hinged Articulated Offshore Tower

2008 ◽  
Author(s):  
Syed Danish Hasan ◽  
Nazrul Islam ◽  
Khalid Moin
Keyword(s):  
Seismic Analysis ◽  
Offshore Structures ◽  
Random Wave ◽  
Wave Forces ◽  
Offshore Structure ◽  
Concentrated Mass ◽  
Energy Principle ◽  
Rotational Angle ◽  
Sea Bed ◽  
Time Histories

The response of offshore structures under seismic excitation in deep water conditions is an extremely complex phenomenon. Under such harsh environmental conditions, special offshore structures called articulated structures are feasible owing to reduced structural weight. Whereas, conventional offshore structure requires huge physical dimensions to meet the desired strength and stability criteria, therefore, are uneconomical. Articulated offshore towers are among the compliant offshore structures. These structures consist of a ballast chamber near the bottom hinge and a buoyancy chamber just below the mean sea level, imparting controlled movement against the environmental loads (wave, currents, and wind/earthquake). The present study deals with the seismic compliance of a double-hinged articulated offshore tower to three real earthquakes by solving the governing equations of motion in time domain using Newmark’s-β technique. For this purpose Elcentro 1940, Taft 1952 and Northridge 1994 earthquake time histories are considered. The tower is modeled as an upright flexible pendulum supported to the sea-bed by a mass-less rotational spring of zero stiffness while the top of it rigidly supports a deck in the air (a concentrated mass above water level). The computation of seismic and hydrodynamic loads are performed by dividing the tower into finite elements with masses lumped at the nodes. The earthquake response is carried out by random vibration analysis, in which, seismic excitations are assumed to be a broadband stationary process. Effects of horizontal ground motions are considered in the present study. Monte Carlo simulation technique is used to model long crested random wave forces. Effect of sea-bed shaking on hydrodynamic modeling is considered. The dynamic equation of motion is formulated using Lagrangian approach, which is based on energy principle. Nonlinearities due to variable submergence and buoyancy, added mass associated with the geometrical non-linearities of the system are considered. The results are expressed in the form of time-histories and PSDFs of deck displacement, rotational angle, base and hinge shear, and the bending moment. The outcome of the response establishes that seismic sea environment is an important design consideration for successful performance of hinges, particularly, if these structures are situated in seismically active zones of the world’s ocean.

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