Stresses in Stiffened Tubular T Joint of an Offshore Structure

1983 ◽  
Vol 105 (2) ◽  
pp. 177-183 ◽  
Author(s):  
M. R. Shiyekar ◽  
M. Kalani ◽  
R. M. Belkune
Keyword(s):  
Finite Element ◽  
Axial Loading ◽  
Offshore Structures ◽  
Internal Ring ◽  
Joint Models ◽  
Offshore Structure ◽  
T Joints ◽  
Tubular Joint ◽  
Simplified Analysis ◽  
Element Technique

The effect of internal ring stiffeners has been studied theoretically and experimentally for the welded tubular T joints occurring in conventional jacket-type offshore structures. Four welded tubular joint models of T shape, with different diameter ratios, have been tested under axial loading in the branch. The analytical results have been obtained by finite element technique. The results indicate a significant reduction in the stress concentration factor and a fairly uniform transfer of load from branch to the chord. A simplified analysis of stiffener rings have been proposed. The stress results of joints strengthened by ring stiffeners and joint can are compared.

scholarly journals Stress Concentration Factor of A Two-Planar Double KT Tubular Joint due to In-Plane Bending Loading in Steel Offshore Structures

2018 ◽  
Vol 177 ◽  
pp. 01006
Author(s):  
Prastianto Rudi Walujo ◽  
Hadiwidodo Yoyok Setyo ◽  
Fuadi Ibnu Fasyin
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Element Model ◽  
Offshore Structures ◽  
Geometrical Parameters ◽  
Offshore Structure ◽  
Wide Range ◽  
Tubular Joint

The purpose of this study is to investigate the proper Stress Concentration Factor (SCF) of a 60° two-planar DKT tubular joint of a tripod wellhead offshore structure. So far, calculation of SCF for a multi-plane tubular joint was based on the formulation for the simple/uniplanar tubular joints that yield in over/under prediction of the SCF of the joint. This situation in turn decreasing the accuracy of fatigue life prediction of the structures. The SCF is one of the most important parameters in the tubular joint fatigue analysis. The tubular joint is modelled as finite element models with bending loads acting on the braces that cover a wide range of dimensionless geometrical parameters (β, τ, γ). The effect of such parameters on the SCF distribution along the weld toe of braces and chord on the joint are investigated. Validation of the finite element model has shown good agreement to the global structural analysis results. The results of parametric studies show that the peak SCF mostly occurs at around crown 2 point of the outer central brace. The increase of the β leads to decrease the SCF. While the increase of the τ and γ leads to increase the SCF. The effect of parameter β and γ on the SCF are greater than the effect of parameter τ.

Experimental, numerical and parametric studies on stress concentration factors of T-joints under tension

2021 ◽  
pp. 136943322110499
Author(s):  
Feleb Matti ◽  
Fidelis Mashiri
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Numerical Study ◽  
Hot Spot ◽  
Joint Models ◽  
Element Analysis ◽  
T Joints ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Good Agreement

This paper investigates the behaviour of square hollow section (SHS) T-joints under static axial tension for the determination of stress concentration factors (SCFs) at the hot spot locations. Five empty and corresponding concrete-filled SHS-SHS T-joint connections were tested experimentally and numerically. The experimental investigation was carried out by attaching strain gauges onto the SHS-SHS T-joint specimens. The numerical study was then conducted by developing three-dimensional finite element (FE) T-joint models using ABAQUS finite element analysis software for capturing the distribution of the SCFs at the hot spot locations. The results showed that there is a good agreement between the experimental and numerical SCFs. A series of formulae for the prediction of SCF in concrete-filled SHS T-joints under tension were proposed, and good agreement was achieved between the maximum SCFs in SHS T-joints calculated from FE T-joint models and those from the predicted formulae.

Ice rubble attenuation of ice loads on arctic offshore structures

1991 ◽  
Vol 28 (6) ◽  
pp. 881-895 ◽  
Author(s):  
T. T. Wong ◽  
N. R. Morgenstern ◽  
D. C. Segoz
Keyword(s):  
Finite Element ◽  
Field Measurements ◽  
Offshore Structures ◽  
Force Transmission ◽  
Offshore Structure ◽  
Element Analysis ◽  
Ice Load ◽  
Broken Ice ◽  
Transmission Capability ◽  
Ice Force

A state of the art survey of ice rubble mechanics is first presented. This survey covers ice rubble morphology, laboratory testing of ice rubble, the study of the load transmission capability of existing rubble fields, and field measurements in ice rubble surrounding offshore structures. Then, the implementation of a new plasticity model for normally consolidated broken ice into an existing finite element stress analysis code is described. The resulting program is validated using triaxial test data. Using this model, a two-dimensional parametric study on ice force transmission through a grounded ice rubble field is performed. The study shows that, in addition to the mechanical properties of ice rubble, the island or berm geometry may significantly affect the ice load. Key words: constitutive model, finite element analysis, ice load, ice rubble, offshore structure, plasticity.

scholarly journals NUMERICAL CALCULATION OF SEICHE MOTIONS IN HARBOURS OF ARBITRARY SHAPE

1982 ◽  
Vol 1 (18) ◽  
pp. 11
Author(s):  
P. Gaillard
Keyword(s):  
Finite Element ◽  
Numerical Calculation ◽  
Arbitrary Shape ◽  
Wave Pattern ◽  
Offshore Structures ◽  
Experimental Investigations ◽  
Far Field ◽  
Method Of Calculation ◽  
Long Wave ◽  
Element Technique

A new method of calculation of wave diffraction around islands, offshore structures, and of long wave oscillations within offshore or shore-connected harbours is presented. The method is a combination of the finite element technique with an analytical representation of the wave pattern in the far field. Examples of application are given, and results are compared with other theoretical and experimental investigations.

Discussion on two methods for determining static strength of tubular T-joints at elevated temperature

2016 ◽  
Vol 20 (5) ◽  
pp. 704-721 ◽  
Author(s):  
Yongbo Shao ◽  
Haicheng Zhao ◽  
Dongping Yang
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Elevated Temperature ◽  
Critical Temperature ◽  
Mechanical Analysis ◽  
Static Strength ◽  
T Joints ◽  
Hollow Section ◽  
Tubular Joint ◽  
Circular Hollow Section

To predict the static strength of a welded tubular joint at elevated temperature using finite element simulation, two methods in the literature were reported. The first method aims to analyze the static strength of a tubular joint at a specified elevated temperature, and a routine mechanical analysis is carried out by defining the material properties at the specified elevated temperature according to some specifications. This method does not consider the heat transfer process of the tubular joint in a fire condition. The second method is used to determine the static strength of a tubular joint using a combination of transient state heat transfer analysis and mechanical analysis. The tubular joint subjected to a specified load is heated in accordance with ISO 834-1 standard fire curve to fail at a critical temperature, and the specified load is considered as the static strength of the joint at the critical temperature. In this study, a detailed parametric study on the failure process of circular hollow section tubular T-joints at elevated temperature is carried out using finite element method. The static strengths of the circular hollow section T-joint models obtained from the two methods are compared. The comparison shows that the first method produces a higher estimation on the static strength compared to the second method. Finally, the effect of some geometrical parameters, chord stress ratio, and elevated temperature on the difference of the two methods is also investigated.

Numerical Investigation of Static Strength for Tubular Joints Reinforced by Inner Plate

2013 ◽  
Vol 470 ◽  
pp. 547-552 ◽  
Author(s):  
Dong Ping Yang ◽  
Yong Bo Shao ◽  
Feng Le Long ◽  
Geng Qi Niu ◽  
Lu Zhang ◽  
...  
Keyword(s):  
Axial Direction ◽  
Offshore Structures ◽  
Static Strength ◽  
Joint Models ◽  
Element Analysis ◽  
Tubular Joints ◽  
Long Span ◽  
Weld Toe ◽  
Ring Reinforcement ◽  
Tubular Joint

Welded tubular joints are widely used in long-span, space and offshore structures. In a welded tubular joint, the chord is generally subjected to loads in radius direction which are transmitted from the brace members in axial direction. As the strength of the chord in radius direction is generally much weaker than that of the brace in axial direction, failure occurs easily at the weld toe on the chord surface. To improve the bearing capacity of the joint structure, reinforcement is necessary. Several reinforcing methods were reported in the literature, such as doubler or collar plate reinforcement, internal stiffened ring reinforcement and bracket reinforcement etc. This paper presents the strengthening method by inner plate. From finite element analysis of many inner plated reinforced tubular joint models, the efficiency of reinforcement by inner plate is analyzed by comparing the static strength of reinforced models with that of unreinforced models. Based on a parametric study of the static strength of tubular joints reinforced by inner plate, the design considerations on inner plate strengthening tubular joints are also proposed.

Finite Element Model Correlation for Offshore Structures

1992 ◽  
Vol 114 (3) ◽  
pp. 154-164 ◽  
Author(s):  
R. L. Tawekal ◽  
M. M. Bernitsas
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Offshore Structures ◽  
Offshore Structure ◽  
Numerical Predictions ◽  
Large Perturbation ◽  
Large Admissible Perturbations ◽  
Static Deflection Measurements ◽  
Model Correlation

Agreement between measured response of an offshore structure and numerical predictions using an initial finite element model (IFEM) is in general poor. An algorithm is developed, which produces an updated finite element model (UFEM) that is fully correlated with respect to modal and static deflection measurements. An incremental nonlinear methodology based on large admissible perturbations in cognate space is used to produce the UFEM by postprocessing results of the initial FEA. No other FEA or trial and error are required. Iterations within each increment are used only to correct for dependence of hydrodynamic excitation on correlation variables. The UFEM corresponds to a real structure and may differ from the IFEM in response and correlation variables by 100–300 percent depending on correlation measures and structural size. Several numerical applications for three offshore structures are used to assess the strength, limitations, and cost of the large perturbation methodology.

Analysis of Offshore Structures Subjected to Various Types of Sea Wave

2004 ◽  
Author(s):  
K. Kuntiyawichai ◽  
S. Chucheepsakul ◽  
M. M. K. Lee
Keyword(s):  
Finite Element ◽  
Wavelet Analysis ◽  
Dynamic Behaviour ◽  
Time History ◽  
Offshore Structures ◽  
Offshore Platforms ◽  
Wave Loading ◽  
Offshore Structure ◽  
Finite Element Software ◽  
Jacket Structures

The principal aim of this paper is to study the dynamic behaviour of offshore platforms subjected to wave loading. A general review of offshore structure, wave loading and their effects on offshore structures are presented. A brief review on the basics of Wavelet analysis is also mentioned in this study. The techniques for modeling wave loading in finite element analyses are described and discussed in detail. A series of 3D analyses were carried out using the ABAQUS finite element software to study the effects on the dynamic response of the change in support conditions at the seabed. The effects of wave height, wave period and wave velocity on platform behaviour were studied. The results from time history analysis are characterized using Wavelet Analysis in order to obtain the response pattern due to wave loading. These analyses allow the frequency response of the jacket structures to be described in the time domain. These results give a clear view on the response of jacket structure. The important parameters on offshore modeling have also been identified and discussed in this paper. The results presented in this study can be used as a guidance for engineer in order to understand the dynamic behaviour of jacket structures subjected to wave loading.

Static Strength of Concrete-Filled Circle Tubular (CFCT) T-Joints under Axial Loading

2010 ◽  
Vol 163-167 ◽  
pp. 854-857
Author(s):  
Sheng Zhi Song ◽  
Yong Bo Shao
Keyword(s):  
Axial Compression ◽  
Failure Modes ◽  
Axial Loading ◽  
Axial Direction ◽  
Static Strength ◽  
The Finite Element Method ◽  
Joint Models ◽  
T Joints ◽  
Hollow Section ◽  
Weld Toe

For typical tubular T-joint, the common failure generally occurs near the weld toe on the chord surface due to the fact that the stiffness of the chord in radial direction is much smaller than that of the brace in axial direction. In this paper, the static strength of tubular T-joints is improved by filling concrete into the chord. The finite element method is used to investigate the improving effeciency of the static strength for tubular T-joints with filling concrete in the chord under axial compression and tension. Firstly, 6 T-joint models were analyzed to prove that filling concrete in the chord is effective to increase the static strength and the stiffness of T-joints with hollow section. Afterwards, based on the analyzing mechanism for CFCT T-joint under axial compression and tension, the different performances under axial compression and tension between circle hollow tubular T-joint and CFCT T-joint were clarified, and the different failure modes for tubular T-joints with hollow section and CFCT T-joints were compared and analyzed.

Finite Element Validation Studies of BS7910 FAD Method Applied to Welded SHS Joints

2007 ◽  
Author(s):  
Zhengmao Yang ◽  
Seng Tjhen Lie ◽  
Wie Min Gho
Keyword(s):  
Finite Element ◽  
Offshore Structures ◽  
Reduction Factor ◽  
Plastic Collapse ◽  
Surface Cracks ◽  
Collapse Load ◽  
T Joints ◽  
Hollow Section ◽  
Wide Range ◽  
Circular Hollow Section

The failure assessment diagram (FAD) has now been widely accepted and used for the assessment of defects found in metallic structures. In BS7910 (2005), the use of this method for offshore structures has been validated for a range of joint geometries. But these validations are only applicable for circular hollow section (CHS) welded joints. For rectangular or square hollow section (RHS or SHS) joints, there are very few references available in the literature. In this paper, systematic investigations have been carried out for the validation and verification of the FAD curves for SHS T-joints. FAD curves for a wide range of welded SHS T-joints containing surface cracks have been established using the fracture mechanics data generated from the finite element analyses. The range of β ratio of these joints is from 0.3 to 0.8. Therefore, the failure mode is constrained in the chord face yielding. The influence of residual stresses on the plastic collapse load and the FAD curves has also been analyzed. The reduction factor used to calculate the plastic collapse load of the SHS T-joints containing cracks have been quantitatively examined, and the use of the BS7910 (2005) Level 2A FAD for SHS joints containing surface cracks has been validated accordingly.

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