Extreme Response Prediction of Steel Risers Using a Four Parameter Distribution

2017 ◽  
Author(s):  
Miguel Alfonso Calderon Ibarra ◽  
Fernando Jorge Mendes de Sousa ◽  
Luís Volnei Sudati Sagrilo ◽  
Ying Min Low
Keyword(s):  
Case Studies ◽  
Dynamic Behavior ◽  
Water Depth ◽  
Lognormal Distribution ◽  
Extreme Values ◽  
Extreme Value Distribution ◽  
Response Prediction ◽  
Parameter Distribution ◽  
Extreme Response ◽  
Hermite Transformation

Recently, a four-parameter distribution known as the shifted generalized lognormal distribution (SGLD) has been presented in the literature. One of its main advantages is that it covers regions of skewness-kurtosis not covered by other distributions of common use in engineering. In this paper, the performance of this distribution is evaluated in the extreme values’ estimation of the utilization ratios of steel riser sections. Three alternatives for using SGLD are investigated in two case studies of different dynamic behavior. The first one is a SLWR (steel-lazy wave riser) connected to a turret-moored FPSO in 914m water depth, and the second is a SLWR connected to a spread-mooring FPSO in a water depth of 1400m. The results obtained by the SGLD-based analysis, which considered several simulation lengths, are compared to those obtained by means of an extreme value distribution fitted to episodical extremes obtained from many distinct realizations. The results of a traditional Weibull-fitting approach to the response peaks and those obtained with and Hermite transformation-based model are also presented for comparison.

Extreme Response Prediction of Steel Risers Using a Four Parameter Distribution

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Miguel Alfonso Calderon Ibarra ◽  
Fernando Jorge Mendes de Sousa ◽  
Luís Volnei Sudati Sagrilo ◽  
Ying Min Low
Keyword(s):  
Water Depth ◽  
Extreme Values ◽  
Extreme Value Distribution ◽  
Response Prediction ◽  
Parameter Distribution ◽  
New Approach ◽  
Offshore Engineering ◽  
Extreme Response ◽  
Hermite Transformation ◽  
Non Gaussian

Short-term extreme response estimates are required in many areas of ocean and offshore engineering, such as steel risers design. As in many cases, the response in non-Gaussian, a theoretical solution, is usually not readily available for this purpose. Hermite transformation and Weibull-based models, among others, are some alternatives that have been used in connection with sampled response time series. In this work, a new approach is investigated. Recently, a four-parameter distribution known as the shifted generalized lognormal distribution (SGLD) has been presented in the literature. One of its main advantages is that it covers regions of skewness–kurtosis not covered by other distributions of common use in engineering. In this paper, the performance of this distribution is evaluated in the extreme values' estimation of the utilization ratios of steel riser sections. Three alternatives for using SGLD are investigated in two case studies of different dynamic behavior. The first one is a steel-lazy wave riser (SLWR) connected to a turret-moored FPSO (floating, production, storage and offloading unit) in 914 m water depth, and the second is a SLWR connected to a spread-mooring FPSO in a water depth of 1400 m. The results obtained by the SGLD-based analysis, which considered several simulation lengths, are compared to those obtained by means of an extreme value distribution fitted to episodical extremes obtained from many distinct realizations. The results of a traditional Weibull-fitting approach to the response peaks and those obtained with a Hermite transformation-based model are also presented for comparison.

scholarly journals Dynamic Analysis of Composite Rotors

1996 ◽  
Vol 2 (3) ◽  
pp. 179-186 ◽  
Author(s):  
S. P. Singh ◽  
K. Gupta
Keyword(s):  
Stability Analysis ◽  
Dynamic Analysis ◽  
Case Studies ◽  
Dynamic Behavior ◽  
Beam Theory ◽  
Interesting Case ◽  
Layerwise Theory ◽  
Inertia Effects ◽  
Fluid Film Bearings ◽  
Equivalent Modulus

An outline of formulation based on a layerwise beam theory for unbalance response and stability analysis of a multi mass, multi bearing composite rotor mounted on fluid film bearings is presented. Disc gyroscopics and rotary inertia effects are accounted for. Material damping is also taken into account. The layerwise theory is compared with conventionally used equivalent modulus beam theory. Some interesting case studies are presented. The effect of various parameters on dynamic behavior and stability of a composite rotor is presented.

scholarly journals Quantification of operating reserves with high penetration of wind power considering extreme values

2020 ◽  
Vol 10 (2) ◽  
pp. 1693
Author(s):  
Johan S. Obando ◽  
Gabriel González ◽  
Ricardo Moreno
Keyword(s):  
Power Systems ◽  
Wind Power ◽  
Extreme Values ◽  
Extreme Value Distribution ◽  
Test System ◽  
Generalized Extreme Value Distribution ◽  
Mixed Integer ◽  
Linear Quadratic ◽  
High Penetration ◽  
Range Of Values

The high integration of wind energy in power systems requires operating reserves to ensure the reliability and security in the operation. The intermittency and volatility in wind power sets a challenge for day-ahead dispatching in order to schedule generation resources. Therefore, the quantification of operating reserves is addressed in this paper using extreme values through Monte-Carlo simulations. The uncertainty in wind power forecasting is captured by a generalized extreme value distribution to generate scenarios. The day-ahead dispatching model is formulated as a mixed-integer linear quadratic problem including ramping constraints. This approach is tested in the IEEE-118 bus test system including integration of wind power in the system. The results represent the range of values for operating reserves in day-ahead dispatching.

Consideration of Epistemic Uncertainty in Extreme Wave Height Estimation

2014 ◽  
Author(s):  
Ryota Wada ◽  
Takuji Waseda
Keyword(s):  
Gulf Of Mexico ◽  
Observational Data ◽  
Wave Height ◽  
Extreme Values ◽  
Epistemic Uncertainty ◽  
Extreme Value Distribution ◽  
Predictive Distribution ◽  
Extreme Value ◽  
Posterior Predictive Distribution ◽  
Value Estimation

Extreme value estimation of significant wave height is essential for designing robust and economically efficient ocean structures. But in most cases, the duration of observational wave data is not efficient to make a precise estimation of the extreme value for the desired period. When we focus on hurricane dominated oceans, the situation gets worse. The uncertainty of the extreme value estimation is the main topic of this paper. We use Likelihood-Weighted Method (LWM), a method that can quantify the uncertainty of extreme value estimation in terms of aleatory and epistemic uncertainty. We considered the extreme values of hurricane-dominated regions such as Japan and Gulf of Mexico. Though observational data is available for more than 30 years in Gulf of Mexico, the epistemic uncertainty for 100-year return period value is notably large. Extreme value estimation from 10-year duration of observational data, which is a typical case in Japan, gave a Coefficient of Variance of 43%. This may have impact on the design rules of ocean structures. Also, the consideration of epistemic uncertainty gives rational explanation for the past extreme events, which were considered as abnormal. Expected Extreme Value distribution (EEV), which is the posterior predictive distribution, defined better extreme values considering the epistemic uncertainty.

Probabilistic Modeling and Analysis of Riser Collision

2002 ◽  
Vol 124 (3) ◽  
pp. 132-138 ◽  
Author(s):  
Bernt J. Leira ◽  
Tore Holma˚s ◽  
Kjell Herfjord
Keyword(s):  
Water Depth ◽  
Deep Water ◽  
Time Domain ◽  
Collision Frequency ◽  
Joint Modeling ◽  
Fatigue Lifetime ◽  
Modeling And Analysis ◽  
Analysis And Design ◽  
Extreme Response ◽  
Probabilistic Context

Analysis and design of deep-water riser arrays requires that both collision frequency and resulting stresses in the pipes are addressed. Within a probabilistic context, the joint modeling of the current magnitude and surface floater motions must be taken into account. The present paper gives an outline of the general analysis setup, and response statistics obtained as a result of time domain simulations are described. Utilization of the analysis is also discussed in relation to estimation of extreme response and fatigue lifetime. As an example of application, a specific Spar buoy riser configuration at a water depth of 900m is considered.

Tree-dependent extreme values: the exponential case

1990 ◽  
Vol 27 (01) ◽  
pp. 124-133 ◽  
Author(s):  
Vijay K. Gupta ◽  
Oscar J. Mesa ◽  
E. Waymire
Keyword(s):  
Branching Process ◽  
Extreme Values ◽  
Rooted Tree ◽  
Domain Of Attraction ◽  
Extreme Value Distribution ◽  
Value Theory ◽  
Extreme Value ◽  
Extinction Time ◽  
Brownian Excursion ◽  
Weighted Trees

The length of the main channel in a river network is viewed as an extreme value statistic L on a randomly weighted binary rooted tree having M sources. Questions of concern for hydrologic applications are formulated as the construction of an extreme value theory for a dependence which poses an interesting contrast to the classical independent theory. Equivalently, the distribution of the extinction time for a binary branching process given a large number of progeny is sought. Our main result is that in the case of exponentially weighted trees, the conditional distribution of n–1/2 L given M = n is asymptotically distributed as the maximum of a Brownian excursion. When taken with an earlier result of Kolchin (1978), this makes the maximum of the Brownian excursion a tree-dependent extreme value distribution whose domain of attraction includes both the exponentially distributed and almost surely constant weights. Moment computations are given for the Brownian excursion which are of independent interest.

Determination of Short Term Extreme Response Values for Temporary Riser Systems: A Practical Approach

2016 ◽  
Author(s):  
Ali Cetin ◽  
Trond Pytte ◽  
Sveinung Eriksrud
Keyword(s):  
Time Series ◽  
Extreme Values ◽  
Classical Method ◽  
Practical Method ◽  
Rayleigh Distribution ◽  
Relevant Variable ◽  
Extreme Response ◽  
Non Gaussian ◽  
Probability Modelling

Operation limits for temporary riser system are determined according to some probability of exceedance of a relevant variable. Accordingly, consistent statistical analysis and probability modelling of the data is required. The common industry approach is to rely on the classical narrow-banded Gaussian process assumption when considering time series of variables of interest. Thus, the time series peaks are characterized by means of the Rayleigh distribution and the relevant extreme values are estimated based on this. However, non-linearities present in riser systems may yield non-Gaussian (wide-banded) processes, rendering the classical approach inappropriate. In the present work, an approximate and practical method is presented to address above issue. It is demonstrated that the approximate method is capable of consistently estimating the relevant extreme values, even where the classical method comes short.

Dynamic Behavior of Submarine Pipelines Under Laying Operation

1982 ◽  
Vol 104 (4) ◽  
pp. 313-318 ◽  
Author(s):  
N. Suzuki ◽  
N. Jingu
Keyword(s):  
Experimental Study ◽  
Dynamic Behavior ◽  
Water Depth ◽  
Forced Oscillation ◽  
Bending Moment ◽  
Scale Model ◽  
Regular Waves ◽  
Wave Response ◽  
Dynamic Bending

Theoretical and experimental study on dynamic behavior of submarine pipelines under laying operation with articulated stingers is described in this paper. Wave response tests in regular waves and forced oscillation tests in still water were conducted using the 1/20 scale model of 406.4 mm o.d. (16 in. o.d.) pipeline laid in 150 m (500 ft) water depth. The results show that: 1) the maximum dynamic bending moment of pipeline MDmax occur at a stinger roller, 2) dynamic bending moment of pipelines MD at shorter periods are larger than those at longer periods, 3) the values of MD in an over-bend region depend highly upon stinger motion, 4) those of MD in a sag-bend region are less than MD max in an over-bend region, 5) the values of MD/HMY increase as the stinger volume increases and that 6) stinger motion at shorter periods are different from those at longer periods.

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