Effect of stress concentration factors on the structural integrity assessment of multi-planar offshore tubular DKT-joints based on the fracture mechanics fatigue reliability approach

Ahmadi, Hamid; Lotfollahi-Yaghin, Mohammad Ali; Aminfar, Mohammad H.

doi:10.1016/j.oceaneng.2011.08.004

Cited by 45 publications

(12 citation statements)

References 26 publications

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“…An alternative way to obtain SCFs is to use FEA modelling, which is a powerful method to identify the locations of critical points and is ideally suited for the calculation of SCFs in complex geometries. Due to its accuracy and high fidelity, FEA has been increasingly used for the calculation of SCFs in offshore welded structures (Woghiren and Brennan 2009, Hellier et al 2014, Ahmadi et al, 2011a, 2011bLee, 1999). Considering its accuracy, the FEA approach is chosen in this study to calculate SCFs in offshore welded structures.…”

Section: Introductionmentioning

confidence: 99%

Determination of stress concentration factors in offshore wind welded structures through a hybrid experimental and numerical approach

2019

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Offshore wind turbine (OWT) monopile support structures generally consist of steel cans connected together through circumferential welding joints. One critical factor to evaluate the localised increase in stresses is the stress concentration factor (SCF) which depends on the welding quality. The complex welding profiles in OWT monopiles makes the accurate calculation of SCF quite challenging. In this work, an innovative approach for the calculation of SCFs in offshore welded structures is proposed based on combined 3D (three-dimensional) laser scanning technology (LST) and 3D finite element analysis (FEA). The precise geometry of the welded specimens is captured using 3D LST, and then imported into a finite element software to perform 3D FEA modelling to accurately calculate SCFs. A 2D (two-dimensional) FEA model of a typical offshore welded structure with ideal geometry is also developed in this work. In addition to numerically calculate SCFs, the 2D FEA model is further combined with non-linear RSM (response surface method) to derive analytical equations, expressing SCFs of offshore welded structures in terms of key welding parameters. Both LST-FEA3D and RSM-FEA2D models are applied to calculate SCFs in large-scale S-N fatigue welded specimens. The results indicate that the LST-FEA3D approach is capable of capturing the variation of SCFs along the width of the welded specimens and identifying the critical points where fatigue crack is most likely to initiate; and the RSM-FEA2D is valuable and efficient in deriving analytical parametric equations for SCFs.

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Section: Introductionmentioning

confidence: 99%

Determination of stress concentration factors in offshore wind welded structures through a hybrid experimental and numerical approach

2019

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“…In the FM approach, the relationship between crack growth rate and stress intensity factor can be developed using the Paris law as [6], ∆ (1) Where and represent the crack size and the number of load cycles, respectively. Moreover, and are the crack growth parameters, which depend on the material properties and loading conditions [7], [8]. In this equation, ∆ represents the stress intensity range which can be defined as [9],…”

Section: Fatigue Reliability Analysismentioning

confidence: 99%

“…Where ∆ and represent the stress range and the geometry function, respectively. In general, the geometry function depends on the crack geometry, structural geometry, and loading [8]. By plugging Eq.…”

Section: Fatigue Reliability Analysismentioning

confidence: 99%

Different Bayesian Methods for Updating the Fatigue Crack Size Distribution in a Tubular Joint

Khalili

Oterkus

Barltrop

et al. 2020

Journal of Offshore Mechanics and Arctic Engineering

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Offshore platforms are prone to fatigue damage. To evaluate the fatigue damage, these platforms are periodically inspected during the in-service lifetime. Inspection activities provide additional information, which includes detection and measurement of crack size. A Bayesian framework can be used to update the probability distribution of the uncertain parameters such as crack size. After updating the distribution of the crack size, it is possible to improve the estimation of joint reliability. The main purpose of this study is to present different methods of Bayesian inference to update the probability distribution of the crack size using the inspection results and to demonstrate how the results are different. Two different methods are presented; analytical (conjugate) and numerical methods. The advantages and shortcomings of each method are discussed. To compare the results of the analytical and numerical methods, two different situations are considered; updating the crack size distribution for a particular joint and updating the crack size distribution for several joints that have almost the same conditions. Although the proposed methodology can be applied to different kinds of structures, an example of tubular joints in a specific jacket platform is presented to demonstrate the proposed approach and to compare the results of two methods.

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“…Rajasankar et al [4] who applied the reliability analysis to the structural integrity assessment of offshore tubular joints used the log-normal distribution for the SCF with the mean and standard deviation of 10.118 and 2.024, respectively. Ahmadi and Lotfollahi-Yaghin [5] and Ahmadi et al [6] performed fatigue reliability analyses, based on stress-life (S-N) and fracture mechanics (FM) approaches, on two-planar tubular DKT-joints under axial loading. In these papers, a log-normal distribution was assumed for the SCF with the mean and standard deviation of 2.75 and 0.4125, respectively.…”

Section: Assumed Distributions For the Scfs In The Reliability Analysismentioning

confidence: 99%

Probability density functions of SCFs in internally ring-stiffened tubular KT-joints of offshore structures subjected to axial loading

Ahmadi

Mohammadi

Yeganeh

2015

Thin-Walled Structures

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Effect of stress concentration factors on the structural integrity assessment of multi-planar offshore tubular DKT-joints based on the fracture mechanics fatigue reliability approach

Cited by 45 publications

References 26 publications

Determination of stress concentration factors in offshore wind welded structures through a hybrid experimental and numerical approach

Determination of stress concentration factors in offshore wind welded structures through a hybrid experimental and numerical approach

Different Bayesian Methods for Updating the Fatigue Crack Size Distribution in a Tubular Joint

Probability density functions of SCFs in internally ring-stiffened tubular KT-joints of offshore structures subjected to axial loading

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