Numerical study on the compression-bending response of grouted connections in offshore structures

2021 ◽  
Vol 185 ◽  
pp. 106839
Author(s):  
Tao Chen ◽  
Qi Fang ◽  
Chihai Zhang ◽  
Weichao Li ◽  
Zhigang Xiao
Keyword(s):  
Numerical Study ◽  
Offshore Structures ◽  
Bending Response

Numerical Study of the Combined Loading Envelope of a Skirted Spudcan Foundation

2014 ◽  
Author(s):  
Ning Cheng ◽  
Mark J. Cassidy ◽  
Yinghui Tian
Keyword(s):  
Clay Soil ◽  
Numerical Study ◽  
Failure Mechanisms ◽  
Small Strain ◽  
Offshore Structures ◽  
Combined Loading ◽  
Finite Element Analyses ◽  
Failure Envelope ◽  
Foundation Type ◽  
Jack Up

Foundations for offshore structures, such as mobile jack-up units, are subjected to large horizontal (H) and moment (M) loads in addition to changing vertical (V) loads. The use of a combined vertical, horizontal and moment (V-H-M) loading envelope to define foundation capacities has become increasingly applied in recent years. However, there is no study on the skirted spudcan, a new alternative foundation type to the conventional spudcan footing for jack-ups. In this study, the combined V-H-M yield envelope of a skirted spudcan foundation in clay soil is investigated with small strain finite element analyses using 3D modeling. The footing’s uniaxial bearing capacities and failure mechanisms are described. The failure envelope for the combined V-H-M loadings is presented. A comparison of the bearing capacities between the spudcan and skirted spudcan of various dimensions is also presented.

A Comparative Numerical Study on the Bending Response of Aluminium Stiffened Plates With Fixed/Floating Frames

2008 ◽  
Author(s):  
Mohammad Reza Khedmati ◽  
Mehran Rastani
Keyword(s):  
Finite Element ◽  
Maximum Stress ◽  
Numerical Study ◽  
Point Of View ◽  
Stiffened Plates ◽  
Stiffened Plate ◽  
Finite Element Analyses ◽  
Bending Response ◽  
Structural Arrangements

In this paper, different structural arrangements of the transverse frames in an orthogonally stiffened plate are investigated from the bending response point of view. The transverse frames are assumed to be either fixed or floating. Other alternate placements of the transverse frames are also included in the comparative calculations. Stress and deflection contours are obtained via finite element analyses. Finally, some recommendations are outlined comparing the results of maximum stress and deflection with the allowable limits.

A Numerical Study on the Ultimate Strength of Damaged Tubular Bracing Members Under Axial Compression

2018 ◽  
Author(s):  
Ling Zhu ◽  
Jieling Kong ◽  
Qingyang Liu ◽  
Han Yang ◽  
Bin Wang
Keyword(s):  
Ultimate Strength ◽  
Axial Compression ◽  
Numerical Study ◽  
Load Capacity ◽  
Approximate Equation ◽  
Offshore Structures ◽  
Experimental Investigations ◽  
Pipe Length ◽  
Axial Load Capacity ◽  
Parametric Studies

The tubular bracing members of offshore structures may sustain collision damages from the supply ships, which lead to the deterioration of the load carrying capacity of tubular bracing members. This paper presents a numerical simulation of the ultimate strength of damaged tubular bracing members under axial compression with the nonlinear finite element code ABAQUS, based on previous experimental investigations. Parametric studies are conducted to investigate the load capacity of damaged tubular bracing members, by considering the effects of diameter (D), wall thickness (H), pipe length (L) and the damage positions on the ultimate strength of tubular members. It is found that lateral damage can cause great reduction of the axial load capacity of tubular members. In addition, an approximate equation to predict the ultimate strength of tubular members based on the given damage depth is proposed.

A Numerical Study of the Hydrodynamics of Reversing Flows Around a Cylinder

1994 ◽  
Vol 116 (4) ◽  
pp. 202-208 ◽  
Author(s):  
K. Nakajima ◽  
Y. Kallinderis ◽  
I. Sibetheros ◽  
R. W. Miksad ◽  
K. Lambrakos
Keyword(s):  
Experimental Data ◽  
Finite Element Method ◽  
Stokes Equations ◽  
Numerical Study ◽  
Offshore Structures ◽  
Two Dimensions ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Random Behavior ◽  
Marching Scheme

A numerical study of the nonlinear and random behavior of flow-induced forces on offshore structures and experimental verification of the results are presented. The numerical study is based on a finite-element method for the unsteady incompressible Navier-Stokes equations in two dimensions. The momentum equations combined with a pressure correction equation are solved employing fourth-order artificial dissipation with a nonstaggered grid, instead of the more commonly used staggered meshes. The solution is advanced in time with a combined explicit and implicit marching scheme. Emphasis is placed on study of reversing flows around a cylinder. Comparisons with experimental data evaluate accuracy and robustness of the method.

Numerical Study on Vortex-Induced Motions of Semisubmersibles With Three Columns With Different Sections Types

2019 ◽  
Author(s):  
Chenling Tian ◽  
Longfei Xiao ◽  
Mingyue Liu ◽  
Lijun Yang ◽  
Jing Liu
Keyword(s):  
Wind Turbine ◽  
Lift Force ◽  
Transverse Direction ◽  
Numerical Study ◽  
Offshore Structures ◽  
Detached Eddy Simulation ◽  
Fluid Forces ◽  
Eddy Simulation ◽  
Resonance Behavior ◽  
Induced Motion

Abstract Vortex-induced motion (VIM) phenomenon is a great challenge for design and operation of offshore structures subjected to ocean flow. Semi-submersibles with three columns are often applied to the field of wind turbine, suffering VIM motions probably. In recent years, it is showed that many factors have more or less influence on VIM of platforms. A comparison of circular columns with square columns on VIM characteristics of three-column semisubmersibles is carried out using the detached eddy simulation (DES) method via Star-ccm+ software. This paper analyzes motions in the transverse direction and yaw, as well as fluid forces including drag force and fluctuating lift force. The results show that transverse amplitudes of semisubmersible with three square columns are much lower than those of semisubmersible with three circular columns at all incidences. Besides, the authors conclude that the semisubmersible with three square columns do not experience obvious resonance behavior, which is different from the semisubmersible with three circular columns. Besides, galloping phenomenon occurred at large reduced velocities at 0°-incidence for the semisubmersible with three square columns, which is likely not induced by lift force directly. Meanwhile, in these cases, yaw amplitudes are also larger than the others. This may be due to the galloping behavior, which is just a conjecture.

Experimental Investigation of Ice Mass Hydrodynamic Interaction With Offshore Structure in Close Proximity

2015 ◽  
Author(s):  
Tanvir Mehedi Sayeed ◽  
Bruce Colbourne ◽  
Heather Peng ◽  
Benjamin Colbourne ◽  
Don Spencer
Keyword(s):  
Hydrodynamic Interaction ◽  
Impact Load ◽  
Numerical Study ◽  
Numerical Models ◽  
Offshore Structures ◽  
Ocean Engineering ◽  
Offshore Structure ◽  
Area Of Interest ◽  
Close Proximity ◽  
The Impact

Iceberg/bergy bit impact load with fixed and floating offshore structures and supply ships is an important design consideration in ice-prone regions. Studies tend to divide the iceberg impact problem into phases from far field to contact. This results in a tendency to over simplify the final crucial stage where the structure is impacted. The authors have identified knowledge gaps and their influence on the analysis and prediction of iceberg impact velocities and loads (Sayeed et. al (2014)). The experimental and numerical study of viscous dominated very near field region is the main area of interest. This paper reports preliminary results of physical model tests conducted at Ocean Engineering Research Center (OERC) to investigate hydrodynamic interaction between ice masses and fixed offshore structure in close proximity. The objective was to perform a systematic study from simple to complex phenomena which will be a support base for the development of subsequent numerical models. The results demonstrated that hydrodynamic proximity and wave reflection effects do significantly influence the impact velocities at which ice masses approach to large structures. The effect is more pronounced for smaller ice masses.

An Extension of the BWH Instability Criterion: Numerical Study

2015 ◽  
Author(s):  
Martin Storheim ◽  
Hagbart Alsos ◽  
Odd Sture Hopperstad ◽  
Jørgen Amdahl
Keyword(s):  
Numerical Study ◽  
Computational Cost ◽  
Offshore Structures ◽  
Instability Criterion ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Stiffened Panel ◽  
Uniaxial Tensile Test ◽  
Large Element ◽  
Good Prediction

The BWH criterion for simulating instability prior to necking in sheet metal has been extended with a post-necking damage model, in which the effect of the local neck inside a large element is accounted for with low mesh dependency. The model is incorporated in the explicit FE code LS-DYNA. The material model can be calibrated from a single uniaxial tensile test, and gives good prediction of rupture for a range of stress triaxialities. This paper investigates the robustness of the criterion through numerical simulations of different experiments, from forming limit tests to large impact experiments on stiffened panel structures. A full-scale collision is simulated with two different mesh-sizes to investigate the robustness of the fracture prediction. The validation cases are simulated with good accuracy considering the coarse meshes involved. Based on the validation, the post-necking extension of the BWH criterion can readily be used for structural design of offshore structures in order to assess the technical safety level of the structure against collisions in all phases of the design process. The method has a good ratio of accuracy vs. computational cost, and is less prone to user-errors as the calibration is simple and the mesh-scaling is automated.

Estimation of sea‐floor wave velocities and density from pressure and particle velocity by AVO analysis

Geophysics ◽  
1995 ◽  
Vol 60 (5) ◽  
pp. 1575-1578 ◽  
Author(s):  
Lasse Amundsen ◽  
Arne Reitan
Keyword(s):  
Numerical Study ◽  
Offshore Structures ◽  
P Wave ◽  
Rock Properties ◽  
Sea Floor ◽  
S Waves ◽  
Interface Waves ◽  
Wave Velocities ◽  
Sea Bottom ◽  
Sea Bed

Sea‐bottom properties play an important role in fields as diverse as underwater acoustics, earthquake and geotechnical engineering, and marine geophysics. Water‐column acousticians study shear and interface waves in the nearbottom sediments with the aim of inferring sea‐bed geoacoustic parameters for predicting reflection and absorption of waves at the sea floor. On the other hand, geotechnical engineers working on design and siting of offshore structures focus on these waves to characterize soil and rock properties. In the field of geophysics, sea‐bottom parameters are of interest for several reasons. In conventional marine acquisition, these parameters determine the partitioning of the incident P‐wave energy from the source into transmitted P‐waves and mode‐converted S‐waves (Tatham and Goolsbee, 1984; Kim and Seriff, 1992). The sea‐floor P‐ and S‐wave velocities and density are also necessary inputs for decomposing multicomponent sea‐floor data into P‐ and S‐waves (Amundsen and Reitan, 1995a and b), as well as in the numerical study of wave propagation phenomena.

scholarly journals Design and prototype of a magnetic adhesion tracked-wheel robotic platform for mooring chain inspection

2018 ◽  
Vol 232 (8) ◽  
pp. 1063-1074 ◽  
Author(s):  
Mahesh Dissanayake ◽  
Tariq Sattar ◽  
Tat-Hean Gan ◽  
Ivan Pinson ◽  
Shehan Lowe
Keyword(s):  
Numerical Study ◽  
Offshore Structures ◽  
Daily Basis ◽  
Maximum Speed ◽  
Robotic Platform ◽  
Destructive Testing ◽  
Integrity Assessment ◽  
Tidal Waves ◽  
Mooring Chain ◽  
Magnetic Adhesion

The development of climbing robots for mooring chain applications is still in its infancy due to the operational complexity and the geometrical features of the chain. Mooring chains are subjected to high tidal waves, harsh environmental conditions and storms on a daily basis. Therefore, the integrity assessment of chain links is vital and regular inspection is mandatory for offshore structures. The magnetic adhesion tracked-wheel crawler robot presented in this study is suitable for mooring chain climbing in air and the technique can be adapted for underwater use. The robotic platform can climb mooring chains at a maximum speed of 42 cm/min with an external load of 50 N. A numerical study was conducted to investigate the adhesion module and analysis of the robot structural design. Numerical results were validated using a prototyped robot in laboratory conditions. The proposed robot can be used as a platform to convey equipment for non-destructive testing applications.

Numerical Study of Wave-Driven Impact of a Sea Ice Floe on a Circular Cylinder

2016 ◽  
Author(s):  
Biao Su ◽  
Karl Gunnar Aarsæther ◽  
David Kristiansen
Keyword(s):  
Numerical Model ◽  
Circular Cylinder ◽  
Sea Ice ◽  
Numerical Study ◽  
Offshore Structures ◽  
Experimental Result ◽  
Recent Experimental Study ◽  
Pressure Area ◽  
Closed Form Analytical Solution ◽  
The Impact

This paper presents a numerical model for simulating wave-driven ice floe–structure interactions, which is integrated in a software framework (FhSim) for time-domain simulation of marine systems. The FhSim framework has proved to be a valuable tool for research and development within different applications and areas [1]. In this study, the wave-driven impact of a sea ice floe on a circular cylinder is simulated. The simulation setup refers to a recent experimental study [2], and the kinematics of ice floe in wave is compared with the experimental result. As the impact forces were not measured in the experiment, a closed-form analytical solution proposed by ISO/FDIS 19906 (Arctic offshore structures) is used for comparison. These comparisons indicate that the present numerical model is able to reproduce the ice floe kinematics and impact characteristics during floe–structure interaction. Furthermore, a sensitivity analysis is conducted, aimed at investigating how much the simulated impact force is affected by variations in the pressure–area relationship.

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