Stochastic Analysis of Offshore Steel Structures

Karadeniz, H.

doi:10.1007/978-1-84996-190-5

Cited by 19 publications

(20 citation statements)

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“…For a better curve fitting to the fatigue test data, a multi-segmented S-N line approach sketched in Fig. 1(a) is applied in the present study [7,18,28], which is defined as follows:…”

Section: S-n Curve Approach and Cumulative Fatigue Damage Rulementioning

confidence: 99%

“…In this model, there is consistent one-to-one match between the fatigue life , and the hot-spot stress range with the constant amplitude ∆ . In practice, ∆ is determined by the nominal stress range (∆ ) and the stress concentration factor [29], which can be estimated from finite element analysis [18]. Furthermore, having defined a relation between ∆ and as presented above, the Palmgren-Miner' rule [25,30] is commonly applied to predict the cumulative fatigue damage under different stress ranges in practice.…”

Section: S-n Curve Approach and Cumulative Fatigue Damage Rulementioning

confidence: 99%

“…Fatigue is defined as a process of damage accumulation under fluctuating stress histories, which eventually results in failure. Nonetheless, the maximum working stress usually remains below the ultimate elastic limit [18]. Three fatigue damage evaluating methods are widely used to explore and determine whether the offshore structures are in a safe and reliable working condition: deterministic analysis method, frequency-domain analysis method (FDA method, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Fatigue assessment on local components of a semi-submersible platform subjected to wind and wave loads

Ma¹,

Zhou²,

Bao³

et al. 2018

J. vibroeng.

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The objective in this work is to assess fatigue damages on local components of a semi-submersible platform under combined actions of wind and wave loads in time domain. Some improvements are provided in the present study to improve the efficiency and accuracy of the whole evaluating process. Firstly, a combined wind and wave relationship as well as an innovative mixture simulation method are used to generate time series of random wind and waves. Moreover, an m-block division method is proposed to compress the number of the whole short-term sea states in the wind-wave scatter diagram. Then, with an improved multiple interpolation sub-model method, the structural stress responses of the local structural components are calculated as is in the whole model analysis. Finally, a modified rain-flow counting method is provided and validated to count the stress cycles efficiently and accurately. Thus, the short-and long-term fatigue damages are computed based on the S-N curve approach and the cumulative fatigue damage rule. In relative agreement with the numerical results by the traditional time-domain method and existing experimental data, these proposed improved methods are demonstrated to be applicable and efficient methods for fatigue damage analyses. All the fatigue damages on local components satisfy the specification requirements and the minimum value appears under the up wind-wave state, which is the proper working condition for a semi-submersible platform.

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“…For a better curve fitting to the fatigue test data, a multi-segmented S-N line approach sketched in Fig. 1(a) is applied in the present study [7,18,28], which is defined as follows:…”

Section: S-n Curve Approach and Cumulative Fatigue Damage Rulementioning

confidence: 99%

Section: S-n Curve Approach and Cumulative Fatigue Damage Rulementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Fatigue assessment on local components of a semi-submersible platform subjected to wind and wave loads

Ma¹,

Zhou²,

Bao³

et al. 2018

J. vibroeng.

View full text Add to dashboard Cite

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“…The background density f xb will still be obtained analytically as in Sec. (45) where we use the analytical solution of the oscillator with nonzero initial velocity n…”

Section: Numerical Computation Of Rare Events Statisticsmentioning

confidence: 99%

“…Excitation. For a stationary Gaussian process with arbitrary spectral bandwidth , the probability density function of positive extrema (maxima) is given by [44,45]…”

Section: Distribution Of Local Maxima Under Backgroundmentioning

confidence: 99%

Heavy-Tailed Response of Structural Systems Subjected to Stochastic Excitation Containing Extreme Forcing Events

Joo

Mohamad

Sapsis

2018

Journal of Computational and Nonlinear Dynamics

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We characterize the complex, heavy-tailed probability density functions (pdfs) describing the response and its local extrema for structural systems subject to random forcing that includes extreme events. Our approach is based on recent probabilistic decomposition-synthesis (PDS) technique (Mohamad, M. A., Cousins, W., and Sapsis, T. P., 2016, “A Probabilistic Decomposition-Synthesis Method for the Quantification of Rare Events Due to Internal Instabilities,” J. Comput. Phys., 322, pp. 288–308), where we decouple rare event regimes from background fluctuations. The result of the analysis has the form of a semi-analytical approximation formula for the pdf of the response (displacement, velocity, and acceleration) and the pdf of the local extrema. For special limiting cases (lightly damped or heavily damped systems), our analysis provides fully analytical approximations. We also demonstrate how the method can be applied to high dimensional structural systems through a two-degrees-of-freedom (TDOF) example system undergoing extreme events due to intermittent forcing. The derived formulas can be evaluated with very small computational cost and are shown to accurately capture the complicated heavy-tailed and asymmetrical features in the probability distribution many standard deviations away from the mean, through comparisons with expensive Monte Carlo simulations.

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Four‐Helix Triboelectric Nanogenerator Based on Wave Amplitude Amplifier

Zhou,

Tuo,

Tang

et al. 2024

Advanced Energy Materials

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Deploying triboelectric nanogenerator (TENG) units on and below the water surface has been a conventional method for harvesting wave energy. However, this approach restricts the TENG's amplitude to that of the water waves, limiting the actual offshore output. Here, a new method of placing TENG units above the water surface using a wave amplitude amplifier is reported. This addresses the issue of insufficient amplitude in traditional wave energy TENGs and achieves higher electrical output performance in real offshore conditions. Moreover, the innovative four‐helix TENG (FH‐TENG), designed with special pattern cutting and bridging techniques, eliminates the need for internal wires, foundational frameworks, and counterweights. Results show that FH‐TENG placed on the amplitude amplifier achieves over a 76% increase in amplitude and a 235% enhancement in charge output compared to FH‐TENG floating directly on the water surface, and the maximum output voltage, transferred charge and output current reach 246 V, 7.9 µC, and 156.1 µA, respectively. Importantly, when deployed in real marine environments, this system generates more electric energy than in a lab pool under the same peak wave height, providing a reliable power supply solution. This work establishes a precedent for deploying lightweight wave energy TENGs above the water surface.

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Stochastic Analysis of Offshore Steel Structures

Cited by 19 publications

References 0 publications

Fatigue assessment on local components of a semi-submersible platform subjected to wind and wave loads

Fatigue assessment on local components of a semi-submersible platform subjected to wind and wave loads

Heavy-Tailed Response of Structural Systems Subjected to Stochastic Excitation Containing Extreme Forcing Events

Four‐Helix Triboelectric Nanogenerator Based on Wave Amplitude Amplifier

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