Biaxial fatigue analysis model under non-proportional phase loading of tensegrity cable domes

2021 ◽  
Vol 245 ◽  
pp. 112791
Author(s):  
N. Logzit ◽  
K. Kebiche
Keyword(s):  
Fatigue Analysis ◽  
Analysis Model ◽  
Biaxial Fatigue ◽  
Cable Domes

Wellhead Fatigue Analysis Method: The Effect of Variation of Lower Boundary Conditions in Global Riser Load Analysis

2012 ◽  
Author(s):  
Lorents Reinås ◽  
Massimiliano Russo ◽  
Guttorm Grytøyr
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Lower Boundary ◽  
Fatigue Analysis ◽  
Analysis Model ◽  
Lower Boundary Condition ◽  
Analysis Methodology ◽  
Well Integrity ◽  
Context Modelling ◽  
Load Analysis

Subsea wellhead mechanical fatigue can potentially result in a gross structural failure of barrier elements in the upper part of the well, potentially resulting in loss of well control. Several major E&P operators have acknowledged the importance of wellhead fatigue and are participating in the JIP “Structural Well Integrity”. It is within the scope of this JIP to develop a recommended practice for wellhead fatigue analysis methodology. The analysis methodology currently being investigated by the JIP is a decoupled approach, with modifications of the lower boundary to account for the stiffness of the conductor, soil and template interface. A detailed local wellhead model is used to generate the lower boundary condition for a decoupled global riser load analysis model. This lower boundary condition definition is intended to capture the overall non-linear stiffness of a site specific well in order to achieve best possible global riser loads estimate. In this article the effect of varying the lower boundary conditions on a global load estimate is studied. Global load estimates are generated from a typical North Sea case and various lower boundary conditions are introduced as the only change to the global riser model. A fixed lower boundary condition is used as a reference and load estimates generated from riser models with various lower boundary conditions are compared. The different lower boundary conditions selected for comparison in this study has been derived from the following cases: 1. Fixed at WH 2. As per ISO 13624-2 3. As per JIP “Structural Well Integrity” -Current 4. As per JIP “Structural Well Integrity” -Modified Comparing the analysis results gives indications that the lower boundary condition modelling approach affect global riser load estimate. The fixed lower end boundary conditions did not yielded the most conservative load history in a fatigue context. Modelling well specific flexibility at the riser lower end increased the total number of wellhead fatigue load cycles. This finding support the current approach suggested by the works of the JIP “Structural Well Integrity”. Ensuring that riser load results are still conservative places a higher importance on precise local modelling of the well system.

Significance of the Relative Orientation of the Mean and Alternating Principal Stress Axes in Biaxial Fatigue

1992 ◽  
Vol 114 (4) ◽  
pp. 406-408 ◽  
Author(s):  
E. G. Munday
Keyword(s):  
Principal Stress ◽  
Fatigue Behavior ◽  
Fatigue Analysis ◽  
Relative Orientation ◽  
Biaxial Fatigue ◽  
Stress Components ◽  
The Mean ◽  
Long Life ◽  
Existing Data

In certain biaxial fatigue problems, the stress components can be represented as a superposition of mean components, and proportionally applied alternating components. Such representation is the first step in applying some of the more popular methods for long-life fatigue analysis. It is commonly assumed, perhaps unwittingly, that the relative orientation of the mean and alternating principal stress axes does not influence fatigue behavior. It is explained how this assumption is inherent in several popular methods. It is pointed out that the validity of the assumption cannot be demonstrated by existing data.

Assessment of the Size Effect in Fatigue Analysis of Butt Welds and Cruciform Joints

2014 ◽  
Author(s):  
Inge Lotsberg
Keyword(s):  
Size Effect ◽  
Fatigue Test ◽  
Test Data ◽  
Hot Spot ◽  
Plate Thickness ◽  
Fatigue Analysis ◽  
Analysis Model ◽  
Design Standards ◽  
Cruciform Joints ◽  
Fatigue Design

Reduced fatigue capacity of welded structures for larger thicknesses was introduced in design standards approximately 30 years ago. A significant amount of research on this topic was performed during the following years. In general the presence of a size effect was agreed upon. The size effect is considered to be dependent on the plate thickness at the considered hot spot in addition to size of attachment plate and type of dynamic loading. Only simplified recommendations on the size effect are included in most fatigue design standards. One reason for this is normal scatter in fatigue test data and also somewhat different recommendations based on these data in the literature. This has made it difficult to arrive at full agreement on recommended fatigue analysis procedures. In this paper a review of literature and design standards are presented together with a calibration of analysis method with fatigue test data. The effect of different parameters contributing to the size effect is illustrated. An attempt has been made to use the calibrated analysis model to also quantify the size effect based on crack growth analyses. Finally some recommendations on size effect to be used in fatigue design standards are presented.

An Input–Process–Output Model of Pilot Core Competencies

2017 ◽  
Vol 7 (2) ◽  
pp. 78-85 ◽  
Author(s):  
Heikki Mansikka ◽  
Don Harris ◽  
Kai Virtanen
Keyword(s):  
Path Analysis ◽  
Team Performance ◽  
Core Competencies ◽  
Core Competency ◽  
Principal Component ◽  
Analysis Model ◽  
Input Process ◽  
The Core ◽  
Performance Framework ◽  
Process Output

Abstract. The aim of this study was to investigate the relationship between the flight-related core competencies for professional airline pilots and to structuralize them as components in a team performance framework. To achieve this, the core competency scores from a total of 2,560 OPC (Operator Proficiency Check) missions were analyzed. A principal component analysis (PCA) of pilots’ performance scores across the different competencies was conducted. Four principal components were extracted and a path analysis model was constructed on the basis of these factors. The path analysis utilizing the core competencies extracted adopted an input–process–output’ (IPO) model of team performance related directly to the activities on the flight deck. The results of the PCA and the path analysis strongly supported the proposed IPO model.

Is That Measure Really One-Dimensional?

Methodology ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 188-196 ◽  
Author(s):  
Esther T. Beierl ◽  
Markus Bühner ◽  
Moritz Heene
Keyword(s):  
Model Fit ◽  
Nuisance Parameters ◽  
Factorial Validity ◽  
Fit Indices ◽  
Analysis Model ◽  
Factor Analysis Model ◽  
One Dimensional ◽  
Confirmatory Factor Analysis Model ◽  
Cutoff Values ◽  
Confirmatory Factor

Abstract. Factorial validity is often assessed using confirmatory factor analysis. Model fit is commonly evaluated using the cutoff values for the fit indices proposed by Hu and Bentler (1999) . There is a body of research showing that those cutoff values cannot be generalized. Model fit does not only depend on the severity of misspecification, but also on nuisance parameters, which are independent of the misspecification. Using a simulation study, we demonstrate their influence on measures of model fit. We specified a severe misspecification, omitting a second factor, which signifies factorial invalidity. Measures of model fit showed only small misfit because nuisance parameters, magnitude of factor loadings and a balanced/imbalanced number of indicators per factor, also influenced the degree of misfit. Drawing from our results, we discuss challenges in the assessment of factorial validity.

Multiaxial fatigue analysis of orthotropic materials

2010 ◽  
Vol 107 (9) ◽  
pp. 369-375 ◽  
Author(s):  
C. Gaier ◽  
B. Unger ◽  
H. Dannbauer
Keyword(s):  
Fatigue Analysis ◽  
Multiaxial Fatigue ◽  
Orthotropic Materials
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