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.

Analysis of Static Strength for Tubular Joint Reinforced with Collar Casing Pipe

2014 ◽  
Vol 578-579 ◽  
pp. 627-630
Author(s):  
Sheng Zhi Song ◽  
Jian Jun Wei ◽  
Wu Sun
Keyword(s):  
Finite Element Analysis ◽  
Failure Modes ◽  
Static Strength ◽  
Mechanism Analysis ◽  
Joint Models ◽  
Element Analysis ◽  
Tubular Joints ◽  
The Finite Element Analysis ◽  
Tubular Joint ◽  
Casing Pipe

To improve the static strength of tubular T-joint, the method of reinforcing with collar casing pipe is proposed. The finite element analysis (FEA) models of reinforced and unreinforced tubular joints built by FEA software (ABAQUS) are calculated to investigate the improving efficiency under axial compression and tension. It is found that collar casing pipe can improve the static strength of tubular joint effectively. Afterwards, based on the mechanism analysis of tubular T-joint models, the failure modes and different performances between reinforced and unreinforced models are clarified.

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.

Strength Analysis of Large-Scale Multiplanar Tubular Joints with Inner-Plate Reinforcement

2009 ◽  
Vol 24 (3) ◽  
pp. 161-177 ◽  
Author(s):  
Shao Yong-Bo ◽  
Zhang Ji-Chao ◽  
Qiu Zhi-Heng ◽  
Shang Jie-Juan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Large Scale ◽  
Failure Process ◽  
Axial Direction ◽  
Strength Analysis ◽  
Element Analysis ◽  
Critical Position ◽  
Tubular Joints ◽  
Tubular Joint

For large scale multiplanar tubular joints used in practical engineering, the brace/chord intersection is a critical position as failure usually occurs here due to the weak bearing capacity of the chord in radius direction compared to the strength of the braces in axial direction. To improve the ultimate strength, different reinforcements can be used to strengthen the structures. Inner plate reinforcement is a relatively new strengthening method compared to conventional reinforcing methods. As there is no corresponding guideline which can be used for the design of inner plate reinforcing joints, it is necessary to investigate the failure mechanism of such tubular structures. Both experimental test and finite element analysis are carried out in this study to investigate the static behaviour of multiplanar tubular joint reinforced with inner plate. In the experimental work, the stresses distribution and development of the specimen is monitored, and the failure mode is observed. From the experimental results, both the failure process of the multiplanar tubular joint and the reinforcing efficiency of the inner plate were analyzed. Using finite element analysis, the failure process of the specimen is also analyzed step by step. The finite element results agree reasonably well with experimental measurements.

Neural Networks for Tubular Joint Optimization in Offshore Jacket Structures

2016 ◽  
Author(s):  
Niels Hørbye Christiansen ◽  
Benny Korsholm Tang
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Design Space ◽  
Joint Optimization ◽  
Joint Models ◽  
Tubular Joints ◽  
Design Variables ◽  
The Neural Network ◽  
Jacket Structures ◽  
Tubular Joint

The use of jacket structures to support offshore installations has for a long time been a popular choice in places with appropriate water depths. In recent years the use of jacket structures as offshore wind turbine foundations has also attracted increasing attention and is becoming a feasible alternative to traditional monopile foundations. One of the key challenges in jacket design is optimizing tubular joints in terms of fatigue resistance. As it is not practically possible to include detailed FEM joint models in global jacket models designers are forced to look for alternative methods to obtain realistic joint representations. This is done by calculating influence factors (INF) and stress concentration factors (SCF) to be applied to simplified models of relevant tubular joints in global models in order to achieve a realistic force flow in the structure. One simple and widely used method is to apply parametric formulas, e.g. those suggested by Efthymiou. However, these approximating formulas have a fairly limited validity range. Therefore, on complex joint the most reliable way to determine INF’s is by setting up refined FEM models of relevant joints and then subsequently using the calculated factors in the global model. This strategy is computationally demanding and hence, very time consuming, as a new detailed FEM analysis of the tubular joint must be conducted for each step in the optimization process. The present paper demonstrates how this time consuming procedure can be avoided by use of artificial neural networks (ANN) trained to estimate INF’s on tubular joints. The neural network is trained on a pre-generated library of detailed FEM joint models and is then able to predict INF’s on joints that are not part of the library — and thereby providing a significant reduction in calculation time during the jacket/joint optimization process. The analysis is conducted on a typical joint on a three legged jacket structure. The joint is located on a jacket leg and has two incoming braces. Such a joint has a finite number of free design variables, e.g. chord diameter/thickness, brace diameter/thickness, brace angle, gap etc. Each of these free variables can be considered as a dimension in the joint design space. Having a sufficient number of FEM joint models in the library the neural network can be trained to recognize and predict underlying patterns in this design space. The method is demonstrated on a limited number of design variables but should easily be extended to cover all variables as the joint library is expanded to include all dimensions.

Fatigue reliability assessment of tubular joints of existing offshore structures

2001 ◽  
Vol 28 (4) ◽  
pp. 691-698 ◽  
Author(s):  
A A Aghakouchak ◽  
S F Stiemer
Keyword(s):  
Decision Making ◽  
Reliability Assessment ◽  
Offshore Structures ◽  
Fatigue Reliability ◽  
Inspection Planning ◽  
Additional Information ◽  
Linear Elastic ◽  
Tubular Joints ◽  
Elastic Fracture ◽  
Tubular Joint

Tubular joints of offshore structures are prone to fatigue damage. Because of uncertainties involved in quantifying the fatigue process in this type of structure, a reliability approach may be adopted to assess the risks of failure. In-service inspections of structures produce additional information, which may be taken into consideration in order to update the reliability. The paper reviews the methods for carrying out such reliability analyses based on principles of linear elastic fracture mechanics and applies them to a sample tubular joint. The results of this type of analyses may be used for inspection, planning, and (or) decision making regarding repairs or modification of the service life of a structure.Key words: fatigue, reliability, tubular joints, offshore structures, condition assessment.

scholarly journals Fatigue Strength Curve for Tubular Joints of Offshore Structures under Dynamic Loading

Dynamics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 125-133
Author(s):  
Sudath C. Siriwardane ◽  
Nirosha D. Adasooriya ◽  
Dimitrios Pavlou
Keyword(s):  
Fatigue Strength ◽  
Hot Spot ◽  
Offshore Structures ◽  
Hot Spot Stress ◽  
Tubular Joints ◽  
Jacket Structures ◽  
Strength Curve ◽  
Tubular Joint ◽  
Stress Concentration Factors

Offshore structures are subjected to dynamic environmental loads (wave and wind loads). A stress-life fatigue strength curve is proposed for tubular joints which are in the splash zone area of offshore jacket structures. The Det Norske Veritas (DNV) offshore structures standards given design T-curve in the air is modified with the environment-dependent parameters to obtain this fatigue strength curve. Validity of the curve is done by comparing fatigue lives given by the proposed curve with experimental fatigue lives of tubular joints tested in seawater under different loading conditions. The fatigue assessment of a case study tubular joint is performed using the proposed curve. Nominal stress ranges of the members, which are connected to the joint, are obtained by dynamic analysis of the jacket structure. Stress concentration factors are utilized with the nominal stresses to obtain the hot spot stress ranges. Fatigue lives are calculated and compared with the conventional approach. Hence the applicability and significance of the proposed fatigue strength curve are discussed.

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 Static Behaviors of a Long-span Cable-Stayed Bridge with a Floating Tower under Dead Loads

2020 ◽  
Vol 8 (10) ◽  
pp. 816 ◽  
Author(s):  
Minseo Jang ◽  
Yunwoo Lee ◽  
Deokhee Won ◽  
Young-Jong Kang ◽  
Seungjun Kim
Keyword(s):  
Structural Characteristics ◽  
Load Ratio ◽  
Offshore Structures ◽  
Axial Stiffness ◽  
Outer Diameter ◽  
Element Analysis ◽  
Long Span Bridges ◽  
Long Span ◽  
The Difference ◽  
The Stability

Owing to the structural characteristics of floating-type structures, they can be effectively applied to overcome the limitation of conventional long-span bridges in deep water. Unlike cable-supported bridges with fixed towers, floating cable-supported bridges show relatively large displacements and rotations under the same load because of floating towers; moreover, the difference in the support stiffness causes differences in the behavior of the superstructures. In addition, the risk of overturning is greater than in conventional floating offshore structures because the center of gravity of the tower is located above the buoyancy center of the floater. A floating cable-supported bridge in which the tether supports the floating main tower is directly influenced by the tether arrangement, which is very important for the stability of the entire structure. In this study, according to the inclined tether arrangement, the outer diameter of the floater, and the buoyancy vertical load ratio (BVR), the static behavioral characteristics of the long-span cable-stayed bridges with floating tower are evaluated through nonlinear finite-element analysis. When the intersection of the tension line of the tether and a pivot point of the tower coincide, the tethers can no longer resist the tower’s rotation. For this reason, a large displacement occurs to equilibrate the structure, and further increases as it approaches the specific slope, even if it is not exactly the specific tether slope. The analytical model of this study indicates that, in terms of increasing the rotational stiffness of the main tower, it is advantageous to increase the floater diameter until a BVR of 1.8 is reached and to increase the axial stiffness of the tether from a BVR of 2.0 or higher.

Effect of Stress Distribution on Fatigue Life of Tubular Joints in Offshore Engineering

2007 ◽  
Vol 348-349 ◽  
pp. 897-900
Author(s):  
Yong Bo Shao
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Stress Distribution ◽  
Intensity Factor ◽  
Failure Process ◽  
Tubular Joints ◽  
Offshore Engineering ◽  
Weld Toe ◽  
Tubular Joint

In the assessment of fatigue life of tubular joints in offshore engineering, hot spot stress range, in conventional method, is frequently used to predict the number of cycles that a tubular joint can sustain before failure from corresponding S-N curves. This method only considers the effect of the peak stress at the weld toe on the fatigue life of a tubular joint, but ignores that of the stress distribution along the weld toe. The effect of the stress distribution along the weld toe on the fatigue life of tubular joints can be evaluated indirectly by analyzing a fracture mechanics parameter, namely stress intensity factor. The stress intensity factor values of the surface cracks in the fatigue failure process for tubular joints subjected to different loading types, thus causing the difference of the stress distributions along the weld toe, are investigated from both numerical analysis and experimental measurement. The results show that the stress distribution along the weld toe has remarkable effect on the fatigue life of tubular joints.

Stress Concentration Factors in T and K-T Tubular Joints Using Finite Element Analysis

1988 ◽  
Vol 110 (4) ◽  
pp. 246-254 ◽  
Author(s):  
O. D. Dijkstra ◽  
R. S. Puthli ◽  
H. H. Snijder
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Axial Load ◽  
Bending Moment ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Tubular Joints ◽  
Tubular Joint ◽  
Concentration Factors ◽  
Stress Concentration Factors

Stress concentration factors (SCFs) in a T and a K-T tubular joint have been determined using the finite element method (FEM). The SCFs are determined for basic load cases (axial load or bending moment) in one of the braces or in the chord. The results of the FEM are compared with available experimental data and with parametric formulas. The T-joint results for brace loadings agree reasonably with the parametric formulas. The K-T joint results for in-plane bending agree reasonably with the parametric formulas.

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