Offshore Pile Foundation Subjected to Lateral Cyclic Load in Layered Soil

2014 ◽  
Vol 891-892 ◽  
pp. 24-29 ◽  
Author(s):  
Sudip Basack ◽  
Abhik Kumar Banerjee
Keyword(s):  
Numerical Model ◽  
Pile Foundation ◽  
Loading Condition ◽  
Cyclic Load ◽  
Complex Loading ◽  
Offshore Structures ◽  
Layered Soil ◽  
Interactive Performance ◽  
Parametric Studies ◽  
Combined Action

The pile foundations supporting offshore structures are required to be designed against cyclic load, moments and torques initiated by a combined action of waves, wind, tides, currents, etc. Such a complex loading condition produces progressive degradation in the pile-soil interactive performance which is likely to introduce significant reduction in bearing capacity with increased settlement and displacements. This paper is based on a numerical model developed by the Authors to study the response of pile foundation under lateral cyclic load in layered soil. The model is validated with a field test data and thereafter, parametric studies have been carried out. A brief description of the works conducted and the major conclusions drawn are highlighted in this paper.

Analysis and Design of Offshore Pile Foundation

2014 ◽  
Vol 891-892 ◽  
pp. 17-23 ◽  
Author(s):  
Sudip Basack
Keyword(s):  
Pile Foundation ◽  
Complex Loading ◽  
Offshore Structures ◽  
Laboratory Model ◽  
Element Analysis ◽  
Analysis And Design ◽  
Theoretical Investigations ◽  
Experimental Laboratory ◽  
Combined Action ◽  
Ocean Environment

The ocean environment necessitates the pile foundation supporting the offshore structures to be designed against cyclic load, moments and torques initiated by a combined action of waves, wind, tides, currents, etc. Such a complex loading condition induces progressive degradation in the pile-soil interactive performance introducing significant reduction in bearing capacity with increased settlement and displacements. The Author has carried out extensive experimental (laboratory model tests) and theoretical investigations (boundary element analysis) to study the salient features of this degradation and developed a design methodology for offshore pile foundation. The works conducted and the major conclusions drawn are highlighted in this paper.

Development and Performance Study of an Apparatus for Imparting Lateral Cyclic Load on Model Pile Foundation

2006 ◽  
Author(s):  
Sudip Basak
Keyword(s):  
Pile Foundation ◽  
Cyclic Load ◽  
Pile Group ◽  
Offshore Structures ◽  
Performance Study ◽  
Model Pile ◽  
New Apparatus ◽  
Group A ◽  
And Performance ◽  
Strength And Stiffness

The environment prevalent in ocean necessitates the pile foundations supporting offshore structures to be designed against lateral cyclic loading initiated by wave action. Such quasi-static load reversal induces deterioration in the strength and stiffness of the soil-pile system introducing progressive reduction in the bearing capacity as well as settlement of the pile foundation. To understand the effect of lateral cyclic load on pile group, a new apparatus, consisting of mechanically and electrically controlled components, has been designed and fabricated. Each of the components of this apparatus is calibrated and a series of trial tests are performed for its performance study. This paper presents detailed description of the apparatus, calibration and operating principle of each of its components, the observations made from trial experiments and the relevant conclusions drawn therefrom.

scholarly journals Preliminary Results on the Dynamics of a Pile-Moored Fish Cage with Elastic Net in Currents and Waves

2020 ◽  
Vol 9 (1) ◽  
pp. 14
Author(s):  
Gianluca Zitti ◽  
Nico Novelli ◽  
Maurizio Brocchini
Keyword(s):  
Numerical Model ◽  
Laboratory Experiments ◽  
Numerical Models ◽  
Offshore Structures ◽  
Fish Farm ◽  
Maximum Displacement ◽  
Drag Forces ◽  
Real Size ◽  
Lift And Drag ◽  
Mesh Grid

Over the last decades, the aquaculture sector increased significantly and constantly, moving fish-farm plants further from the coast, and exposing them to increasingly high forces due to currents and waves. The performances of cages in currents and waves have been widely studied in literature, by means of laboratory experiments and numerical models, but virtually all the research is focused on the global performances of the system, i.e., on the maximum displacement, the volume reduction or the mooring tension. In this work we propose a numerical model, derived from the net-truss model of Kristiansen and Faltinsen (2012), to study the dynamics of fish farm cages in current and waves. In this model the net is modeled with straight trusses connecting nodes, where the mass of the net is concentrated at the nodes. The deformation of the net is evaluated solving the equation of motion of the nodes, subjected to gravity, buoyancy, lift, and drag forces. With respect to the original model, the elasticity of the net is included. In this work the real size of the net is used for the computation mesh grid, this allowing the numerical model to reproduce the exact dynamics of the cage. The numerical model is used to simulate a cage with fixed rings, based on the concept of mooring the cage to the foundation of no longer functioning offshore structures. The deformations of the system subjected to currents and waves are studied.

Matching Relationship between Shaft Material and Fatigue Properties under Complex Loading Condition

2012 ◽  
Vol 500 ◽  
pp. 484-488
Author(s):  
Wo Bo Zhang
Keyword(s):  
Fatigue Strength ◽  
Carbon Steel ◽  
Loading Condition ◽  
Influence Factors ◽  
Complex Loading ◽  
Fatigue Properties ◽  
Material Fatigue ◽  
Relevant Factors

According to analyzing the influence factors of shaft fatigue properties, the matching relationships between fatigue properties and shaft material as well as other relevant factors have been investigated. And the matching relationships have been demonstrated via experimentation. A useful method is established to enhance material fatigue toughness. Considering the aspects of safety, economy and the requirement of fatigue strength, when the dimension of the structure could not be changed, the fatigue properties can be improved via increasing the fillet of the shaft. And 45 carbon steel is a highly recommended shaft material.

Effect of Surface Finish and Loading Conditions on the Low Cycle Fatigue Life of Stainless Steel Welded Piping in PWR Environment

2013 ◽  
Author(s):  
Yuichi Fukuta ◽  
Yuichiro Nomura ◽  
Seiji Asada
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Austenitic Stainless Steel ◽  
Surface Finish ◽  
Loading Condition ◽  
Low Cycle Fatigue ◽  
Complex Loading ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Effect Of Surface

NUREG/CR-6909 of USA and JSME of Japan proposed new rules for evaluating environmental effects in fatigue analyses of reactors components. These rules were established from a lot of fatigue data with polished specimens under simple loading condition. The effects of surface finish or complex loading condition were reported in some papers, but these data were obtained with the simple shaped specimens. In order to evaluate the effects of surface finish and loading condition and to confirm the applicability of the proposed rules to actual components, Low Cycle Fatigue tests are performed in PWR environment with the specimens cut from 316 austenitic stainless steel welded piping. The pipes are machined to have three levels of surface finish condition and the load pattern simulating the thermal stress is applied to specimens. In this study, the effect of surface finish on fatigue life is included to be small for 316 austenitic stainless steel welded piping. Considering the insensitive region in the current evaluation rule, predicted accuracy is increased and possibility of improving the current rule is indicated.

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.

Sensitivity of Fatigue Assessment to the Use of Different Reference S-N Curves

2003 ◽  
Author(s):  
Xiaozhi Wang ◽  
Zhan Cheng
Keyword(s):  
Loading Condition ◽  
Offshore Structures ◽  
Constant Amplitude ◽  
Fatigue Assessment ◽  
Tubular Joints ◽  
Environment Effects ◽  
Assessment Approach ◽  
The Difference ◽  
Offshore Industry ◽  
Number Of Cycles

The S-N curve based fatigue assessment approach is the most widely used one in both ship and offshore industry, in contrast with a fracture mechanics approach. The S-N approach, implemented by either simplified or spectral method, has to apply S-N curves to calculate fatigue strength. The S-N curve, which represents the number of cycles (N) of a constant amplitude stress range (S) that will cause a fatigue failure, is normally developed based on experimental data. Which S-N curve should be applied to a particular detail depends very much on the geometry of the detail, welding information as well as loading condition. There are various S-N curves published by different institutions, e.g., S-N curves published by UK HSE, IIW, AWS etc. The newly developed ABS “Guidance on Fatigue Assessment of Offshore Structures”, [1], proposes the ABS S-N curves, in which two categories of joints, tubular and non-tubular, are included, and both size and environment effects are taken into account. However, the application in Gulf of Mexico is also influenced by API recommendations. In API RP 2A, AWS S-N curves are referred, which in US practice is accepted for fixed (buoyant and non-buoyant) platform deck structures. The objective of this paper is to address the difference between different S-N curves and to present the detailed results of fatigue assessment by using different S-N curves for non-tubular joints. Conclusions made based on the study provide more background on the S-N curve application in fatigue assessment.

Evaluation of Wind Loads on FPSO Topsides Using a Numerical Wind Tunnel

2016 ◽  
Author(s):  
Daniel Barcarolo ◽  
Yann Andrillon ◽  
Erwan Jacquin ◽  
Alain Ledoux
Keyword(s):  
Boundary Layer ◽  
Numerical Model ◽  
Wind Tunnel ◽  
Atmospheric Boundary Layer ◽  
Scale Effects ◽  
Geometric Model ◽  
Wind Tunnel Test ◽  
Offshore Structures ◽  
Wind Loads ◽  
The Impact

The accurate evaluation of wind loads applied on floating offshore structures is extremely important as they are in specific conditions one of the dimensioning criteria for the mooring design. Nowadays these loads are mainly assessed through wind tunnel tests performed at model scale. Estimating realistic wind loads however, remains a big challenge. The complexity and associated simplification level of FPSO topside structures, the scale effects and the establishment of the atmospheric boundary layer imply that many simplifications are to be made. Typically, the FPSO topside is greatly simplified and equivalent blocs of wired frame are used. Today with the evolution of CFD software, and the increase of the meshing capacity, new scopes open to CFD. Aerodynamic simulations on complex FPSO structures are therefore now possible, but need specific developments and validations that are presented in this paper. The main objective of the work presented is to investigate the ability of CFD to evaluate wind loads on complex FPSOs topsides and to provide information on the impact of model simplifications made in wind tunnels. In a first stage, the numerical model was intensively validated by comparing its results to a wind tunnel test case. The numerical model was developed in order to ensure the quality of the results and enable a relevant comparison that was obtained with grids density up to 30 million cells. For this purpose, the geometric model used corresponds to the one used in wind tunnel. The same Atmospheric Boundary Layer was simulated and a thorough effort was performed to ensure the mesh convergence. In a second stage, more physical aspects of the wind tunnel methodology were investigated. Typically the accuracy of the blockage effect correction was evaluated by performing computations with and without blockage, and results were compared with classical corrections applied in wind tunnel. The impacts of the Atmospheric Boundary Layer on wind loads have also been investigated. Finally, the wind load contribution of each component of the FPSO was evaluated.

scholarly journals SIMPLE METHOD FOR STATIC GROUP FACTOR OF PILE FOUNDATION IN TWO-LAYERED SOIL

2006 ◽  
Vol 71 (604) ◽  
pp. 63-70
Author(s):  
Katsuichiro HIJIKATA ◽  
Tatsuya SUGIYAMA ◽  
Tomoaki ISHIDA ◽  
Fumio YAGISHITA ◽  
Tatsuya MASE
Keyword(s):  
Pile Foundation ◽  
Layered Soil ◽  
Group Factor ◽  
Simple Method ◽  
Static Group
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