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.

Comparing Measured Responses of an Offshore Structure with Operational Modal Analysis assisted Classical Model Approach

2020 ◽  
pp. 1-10
Author(s):  
Bruna Nabuco ◽  
Sandro D. Amador ◽  
Evangelos I. Katsanos ◽  
Ulf T. Tygesen ◽  
Erik Damgaard Christensen ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Modal Analysis ◽  
Element Model ◽  
Operating Conditions ◽  
Operational Modal Analysis ◽  
Mode Shapes ◽  
Wave Forces ◽  
Wave Load ◽  
Offshore Structure

Abstract Aiming to ensure the structural integrity of an offshore structure, wave-induced responses have been measured during normal operating conditions. Operational Modal Analysis is applied to the data obtained from continuously monitoring the structure. Sensors placed only on the topside of an offshore platform are sufficient to provide information to identify the modal properties of the structure, such as natural frequencies, damping ratios, and mode shapes. A finite element model is created and updated in line with the identified dynamic properties for applying a modal expansion technique in the interest of accessing information at any point of the structure. Wave radars are also placed at the platform from which the wave forces are calculated based on basic industrial standard models. In this way, the wave kinematics are estimated according to the linear wave theory associated with Wheeler stretching. Since this study is related to offshore structures composed by slender elements, the wave forces are estimated using Morison formulation. By assigning typical values to the drag and inertia coefficients, wave loads are estimated and applied to the updated finite element model. For the diffraction effect, the wave load has also been evaluated according to MacCamy and Fuchs theory. The responses obtained from this procedure are compared with measured responses. In addition to describing the process, this paper presents a case study to verify the theory using monitoring data from a tripod jacket. Results indicate realistic response estimation that contributes to the knowledge about the state of the structure.

Finite Element Analysis for Structural Performance of Offshore Platforms under Environmental Loads

2013 ◽  
Vol 569-570 ◽  
pp. 159-166 ◽  
Author(s):  
Shehata E. Abdel Raheem ◽  
Elsayed M.A. Abdel Aal
Keyword(s):  
Finite Element ◽  
Return Period ◽  
Wave Force ◽  
Offshore Structures ◽  
Offshore Platform ◽  
Offshore Platforms ◽  
Offshore Structure ◽  
Current Increase ◽  
Environmental Loads ◽  
Highly Nonlinear

Offshore structures for oil and gas exploitation are subjected to various ocean environmental phenomena which can cause highly nonlinear action effects. Offshore structures should be designed for severe environmental loads and strict requirements should set for the optimum performance. The structural design requirements of an offshore platform subjected to wave induced forces and moments in the jacket can play a major role in the design of the offshore structures. For an economic and reliable design; good estimation of wave loadings are essential. The structure is discretized using the finite element method, wave force is determined according to linearized Morison equation. Hydrodynamic loading on horizontal and vertical tubular members and the dynamic response of fixed offshore structure together with the distribution of displacement, axial force and bending moment along the leg are investigated for regular and extreme conditions, where the structure should keep production capability in conditions of the one year return period wave and must be able to survive the 100 year return period storm conditions. The results show that the nonlinear response analysis is quite crucial for safe design and operation of offshore platform. Fixed Jacket type offshore platforms under extreme wave loading conditions may exhibit significant nonlinear behavior. The effect of current with different angles when hitting the offshore structure with the wave and wind forces, is very important for calculate the stress, the response displacement and deformation shapes. As the current increase or decrease the effect of wave force according to the hitting angle of current.

Structural Optimization of the Telescopic Boom of a Certain Type of Truck-Mounted Crane

2014 ◽  
Vol 548-549 ◽  
pp. 383-388
Author(s):  
Zhi Wei Chen ◽  
Zhe Cui ◽  
Yi Jin Fu ◽  
Wen Ping Cui ◽  
Li Juan Dong ◽  
...  
Keyword(s):  
Finite Element ◽  
Static Analysis ◽  
Cross Sections ◽  
Optimization Design ◽  
Structural Parameters ◽  
Vertical Direction ◽  
Element Model ◽  
Shape Parameters ◽  
Conventional Design ◽  
Design Variables

Parametric finite element model for a commonly used telescopic boom structure of a certain type of truck-mounted crane has been established. Static analysis of the conventional design configuration was performed first. And then an optimization process has been carried out to minimize the total weight of the telescopic structures. The design variables include the geometric shape parameters of the cross-sections and the integrated structural parameters of the telescopic boom. The constraints include the maximum allowable equivalent stresses and the flexure displacements at the tip of the assembled boom structure in both the vertical direction and the circumferential direction of the rotating plane. Compared with the conventional design, the optimization design has achieved a significant weight reduction of up to 24.3%.

scholarly journals Experimental Investigation on Hydrodynamic Coefficients of a Column-Stabilized Fish Cage in Waves

2019 ◽  
Vol 7 (11) ◽  
pp. 418
Author(s):  
Zhao ◽  
Chen ◽  
Bi ◽  
Cui
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Drag Force ◽  
Inertial Force ◽  
Element Model ◽  
Wave Force ◽  
Hydrodynamic Coefficients ◽  
Horizontal Wave ◽  
Horizontal Wave Force ◽  
The Finite Element Model

This study on hydrodynamic coefficients of a column-stabilized fish cage under wave action plays an important role in the anti-wave design of cages. The regular wave test was used to study the horizontal wave force of the jacket and column-stabilized fish cage under different wave heights, periods, and incident angles; the finite element model of the jacket and the column-stabilized fish cage was established according to the test model. On the basis of the calculation of the finite element model, combined with the wave force obtained from the experiment, the hydrodynamic coefficients of the structure was fitted by the least squares method, and then the drag force, inertial force, and total force of the structure under different conditions were calculated. The results show that the hydrodynamic coefficients of the jacket and netting under the wave condition were more obvious with the change of the KC number and wave incident angles. And as the wave height increased, the drag force, the inertial force, and the proportion of the drag force to the horizontal wave force both increased. When the wavelength was large, the same trend occured as the wave period increased. When the wave incident angles were different, the forces of the jacket and the column-stabilized fish cage were always small in lateral low-frequency waves, which is consistent with the change law of hydrodynamic coefficients of the jacket and netting.

Experimental Study on the Wave Loads on Monopile and Jacket Type Support of Offshore Wind Turbines

2018 ◽  
Author(s):  
Jing Zhang ◽  
Qin Liu ◽  
Xing Hua Shi ◽  
C. Guedes Soares
Keyword(s):  
Experimental Study ◽  
Wind Turbine ◽  
Nonlinear Wave ◽  
Wave Force ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Forces ◽  
Wave Loads ◽  
Morison Equation ◽  
Offshore Wind Turbines

As the offshore fixed wind turbine developed, more ones will be installed in the sea field with the depth 15–50 meters. Wave force will be one of the main forces that dominate the design of the wind turbine base, which is calculated using the Morison equation traditionally. This method can predict the wave forces for the small cylinders if the drag and inertia coefficients are obtained accurately. This paper will give a series scaled tests of monopile and jacket type base of the offshore wind turbine in tank to study the nonlinear wave loads.

Study on the Motions and Stress of Immersing Tunnel Element under Wave Actions

2013 ◽  
Vol 328 ◽  
pp. 614-622
Author(s):  
Hong Da Shi ◽  
Shui Yu Li ◽  
Dong Wang
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Diffraction Theory ◽  
Wave Force ◽  
Source Distribution ◽  
Wave Forces ◽  
Linear Wave ◽  
Wave Loads ◽  
Distribution Method ◽  
Motion Responses

The dynamic characteristics of large-scale tunnel element are very important for the process of immersion. In the paper, the motions and stress of the element under wave actions were studied. The linear wave diffraction theory and the three-dimensional source distribution method were applied to calculate the wave loads and motion responses of the tunnel element under different incident wave conditions. In the study, there have no cable on the element. On the basis of the above theories, the stress and the motions of the element were studied. The first order wave forces and the second order wave force were deduced, and the motions equation was made.

Finite Element Analysis of Cold Bend Pipes Under Bending Loads

2010 ◽  
Author(s):  
Millan Sen ◽  
Roger Cheng
Keyword(s):  
Finite Element ◽  
Local Buckling ◽  
Vertical Direction ◽  
Element Model ◽  
Element Analysis ◽  
Cold Bending ◽  
Bending Process ◽  
Cold Bends ◽  
Full Scale Tests ◽  
The Right

Cold bends are required in pipelines at locations of changes in horizontal or vertical direction in the right of way. Due to this change of direction, pipeline deformations caused by geotechnical or operational loading conditions tend to accumulate at the site of cold bends. These deformations may become sufficient to cause local buckling at the bend. For pipeline design, it is important to understand the level of deformation that a cold bend can accumulate prior to local buckling so that the strain capacity can be compared to the expected pipeline deformations. Evaluating the buckling strain of cold bends is extremely complex due to the residual stresses, ripples, and material transformations cause by the cold bending process. Accordingly a finite element model was developed herein. This model accounted for the cold bend geometry, initial imperfections, and the material transformations caused by the cold bending process. This model was validated against 7 full scale tests of cold bend pipes that were subjected to bend loading and internal pressure. The global and local behavior of this model exhibited reasonable correlation against the tests.

Analysis of Wave Loads on Pile-Group Foundation

2013 ◽  
Vol 680 ◽  
pp. 217-221 ◽  
Author(s):  
Yi Min Liu
Keyword(s):  
Circular Cylinder ◽  
Incident Wave ◽  
Pile Foundation ◽  
Pile Group ◽  
Wave Force ◽  
Wave Number ◽  
Back Side ◽  
Wave Loads ◽  
Pile Groups ◽  
Diffraction Wave

The grouping pile foundation is widely used in the construction of bridge over sea and its scale of construction is generally dominated by the wave force on the pile groups. Because of the presence of the slab, not only the incident wave but also the diffraction wave should be considered in calculating wave loads on pile groups. The diffraction from a submerged circular cylinder representing the slab was taken as an example, and wave loads on piles in the diffraction wave field were calculated by using Morison formula. Results show that the effect of slab decreases with the increase of incident wave number. Changing laws of different piles in the pile-group foundation varied with the submerged depth. Wave loads at the meeting-wave side of slab is larger than the back side of that. And the presence of slab caused the deflexion of inline force. The grouping piles coefficient can be taken as 0.7.

Investigation of Bearing Characteristics of High-Cap Pile Foundation under Inclined Load

2018 ◽  
Vol 777 ◽  
pp. 559-563
Author(s):  
Yu Zhuo Jia ◽  
Guo Zheng Sun ◽  
Chang Qing Li ◽  
Long Long Tian
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Pile Foundation ◽  
Yellow River ◽  
Three Dimensional ◽  
Pile Group ◽  
Element Model ◽  
Inclined Load ◽  
Finite Element Software ◽  
Inclined Angle

To analyze the characteristics of bearing capacity of high-cap pile foundation under inclined load and investigate the influence of vertical and horizontal component on the foundation at different loading angles, based on the background of the Yellow River Crossing project, a three-dimensional finite element model of high-cap foundation is simulated and analyzed with the finite element software ABAQUS. The conclusions are shown as follows: Under the same displacement condition, when the load inclination angle α from 0°(horizontal load) to 80°, the horizontal direction bearing capacity of the foundation increases from 684.8kN to 759.9kN, increases by 10.97%. Expands of vertical load component will affect the pile group effect, the shear force of the back row piles increases with the load inclined angle.

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