Stochastic Analysis of Nonlinear Responses of a Moored Structure Under Narrow Band Excitations

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Solomon C. Yim ◽  
Dongjun Yuk ◽  
Arvid Naess ◽  
I-Ming Shih
Keyword(s):  
Stochastic Analysis ◽  
Extreme Values ◽  
Narrow Band ◽  
Probability Distributions ◽  
Structural Response ◽  
Nonlinear Behavior ◽  
Random Waves ◽  
Single Output ◽  
Multiple Input ◽  
Semianalytical Method

A semianalytical method is developed for the stochastic analysis of a nonlinear moored ocean structure subjected to narrow band random waves. The method is then used to investigate the probability distribution of extreme values of the responses. To verify the accuracy and capability of the method in handling complex nonlinear behavior of the nonlinear moored ocean structure, experimental results are employed to calibrate numerical simulations and the resulting probability distributions obtained from the semianalytical method. A nonlinear-structure nonlinearly damped model is employed to model the moored structure considered and the system coefficients are identified through the reverse multiple-input/single-output technique. An examination of the comparisons indicates that the structural response extreme value probability distributions obtained from the semianalytical predictions are quite accurate.

Stochastic Analysis of Nonlinear Response of a Moored Structural System Under Narrowband Excitations

2006 ◽  
Author(s):  
Solomon C. Yim ◽  
Dongjun Yuk ◽  
Arvid Naess ◽  
I.-Ming Shih
Keyword(s):  
Analytical Method ◽  
Stochastic Analysis ◽  
Extreme Values ◽  
Probability Distributions ◽  
Structural Response ◽  
Nonlinear Behavior ◽  
Random Waves ◽  
Nonlinear Structure ◽  
Single Output ◽  
Multiple Input

A semi-analytical method is developed for the stochastic analysis of a nonlinear moored ocean structure subjected to narrowband random waves. The method is then used to investigate the probability distribution of extreme values of the responses. To verify the accuracy and capability of the method in handling complex nonlinear behavior of the nonlinear moored ocean structure, experimental results are employed to calibrate numerical simulations and the resulting probability distributions obtained from the semi-analytical method. A nonlinear-structure nonlinearly damped model is employed to model the moored structure considered and the system coefficients are identified through the reverse multiple-input/single-output technique. An examination of the comparisons indicates that the structural response extreme value probability distributions obtained from the semi-analytical predictions are quite accurate.

Effects of Nonlinear Riser-Soil Interaction Model on Fatigue Design of Steel Catenary Riser Under Random Waves

2017 ◽  
Author(s):  
Mehrdad Kimiaei
Keyword(s):  
Oil And Gas ◽  
Structural Response ◽  
Interaction Model ◽  
Nonlinear Behavior ◽  
Random Waves ◽  
Steel Catenary Riser ◽  
Oil And Gas Fields ◽  
Fatigue Design ◽  
Time Histories ◽  
Main Components

Steel Catenary Risers (SCRs) are one of the main components in development of oil and gas fields in deep waters. Fatigue design of SCRs in touch down zone (TDZ) is one of the main engineering challenges in design of riser systems. Nonlinear riser-soil interaction models have recently been introduced and used widely in advanced structural analysis of SCRs. Due to hysteretic nonlinear behavior of the soil, SCR system will show different structural response under different loading time histories. This paper investigates the effects of nonlinear riser-soil interaction in the TDZ on fatigue performance of an example SCR subjected to randomly generated waves. Sensitivity of fatigue life of the system, location of the critical node and the maximum stress range to different wave realizations and different soil types are discussed in detail.

The Motion of Floating Systems: Nonlinear Dynamics in Periodic and Random Waves

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Katrin Ellermann
Keyword(s):  
Dynamical Behavior ◽  
Nonlinear Behavior ◽  
Operating Conditions ◽  
Random Waves ◽  
Multiple Components ◽  
Random Disturbances ◽  
Restoring Forces ◽  
Steady State Responses ◽  
External Forces ◽  
Floating Systems

Floating systems, such as ships, barges, or semisubmersibles, show a dynamical behavior, which is determined by their internal structure and the operating conditions caused by external forces e.g., due to waves and wind. Due to the complexity of the system, which commonly includes coupling of multiple components or nonlinear restoring forces, the response can exhibit inherently nonlinear characteristics. In this paper different models of floating systems are considered. For the idealized case of purely harmonic forcing they all show nonlinear behavior such as subharmonic motion or different steady-state responses at constant operating conditions. The introduction of random disturbances leads to deviations from the idealized case, which may change the overall response significantly. Advantages and limitations of the different mathematical models and the applied numerical techniques are discussed.

Utilizarea teoriei valorilor extreme în climatologie

2019 ◽  
Author(s):  
Valentin Raileanu ◽  
Keyword(s):  
Maximum Likelihood ◽  
Extreme Values ◽  
Probability Distributions ◽  
Simulated Data ◽  
Likelihood Estimation ◽  
R Software ◽  
Data Set ◽  
Data Format ◽  
Generalized Pareto ◽  
Distribution Parameters

The article briefly describes the history and fields of application of the theory of extreme values, including climatology. The data format, the Generalized Extreme Value (GEV) probability distributions with Bock Maxima, the Generalized Pareto (GP) distributions with Point of Threshold (POT) and the analysis methods are presented. Estimating the distribution parameters is done using the Maximum Likelihood Estimation (MLE) method. Free R software installation, the minimum set of required commands and the GUI in2extRemes graphical package are described. As an example, the results of the GEV analysis of a simulated data set in in2extRemes are presented.

scholarly journals Analysis of static structural of ocean FARMITS offshore cage due to environmental load

2018 ◽  
Vol 177 ◽  
pp. 01023
Author(s):  
Yani Purnawanti ◽  
Nur Syahroni ◽  
Yeyes Mulyadi
Keyword(s):  
Maximum Yield ◽  
Structural Response ◽  
Fish Farming ◽  
Frame Structure ◽  
Mooring Line ◽  
Strength Analysis ◽  
Tension Stress ◽  
Random Waves ◽  
Cage Structure ◽  
Static Structure

Consumption of fish in Indonesia continuously increase from 2000 to 2014. Particularly fish farming in Java from 2006-2014 is quite high, so there need to be adequate facilities for fish farming. Responding to these challenges, we developed Offshore Cage Ocean FARMITS technology specifically designed For the southern waters of Java Island. This paper discusses the static structure strength analysis of deformation and maximum yield strength that occurs on the offshore cage structure of Ocean FARMITS. The frame structure made of hollow pipe made from HDPE will be placed at 4,41m Wave Height, with a period of 19s. Numerical simulations are performed to obtain a motion response RAO and structural response due to random waves. This Structure is then analyzed under mooring conditions with the Catenary Mooring configuration. Rope stress that occur due to environmental loads will give tension stress to the structure, resulting in the offshore cage structure to occur maximum stress and deformation. The result of this research is to prove that the structure that is made by HDPE able to restrain the tension force of mooring line stress. This has been validated by the standard of Practical Aspects of Offshore Aquaculture System Design from Aquaculture America, so this structure can be said to be operating safely under Indonesian Irregular Wave.

Estimation Design Using Youla Parametrization With Automotive Applications

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Francis Assadian ◽  
Alex K. Beckerman ◽  
Jose Velazquez Alcantar
Keyword(s):  
Kalman Filtering ◽  
Feedback Stabilization ◽  
Estimation Technique ◽  
Single Input Single Output ◽  
Normal Forces ◽  
Single Output ◽  
Multiple Input ◽  
Single Input ◽  
Established Technique ◽  
Better Than

Youla parametrization is a well-established technique in deriving single-input single-output (SISO) and, to a lesser extent, multiple-input multiple-ouput (MIMO) controllers (Youla, D., Bongiorno, J. J., Jr., and Lu, C., 1974, “Singleloop Feedback-Stabilization of Linear Multivariable Dynamical Plants,” Automatica, 10(2), pp. 159–173). However, the utility of this methodology in estimation design, specifically in the framework of controller output observer (COO) (Ozkan, B., Margolis, D., and Pengov, M., 2008, “The Controller Output Observer: Estimation of Vehicle Tire Cornering and Normal Forces,” ASME J. Dyn. Syst., Meas., Control, 130(6), p. 061002), is not established. The fundamental question to be answered is as follows: is it possible to design a deterministic estimation technique using Youla paramertization with the same robust performance, or better, than well-established stochastic estimation techniques such as Kalman filtering? To prove this point, at this stage, a comparative analysis between Youla parametrization in estimation and Kalman filtering is performed through simulations only. In this paper, we provide an overview of Youla parametrization for both control and estimation design. We develop a deterministic SISO and MIMO Youla estimation technique in the framework of COO, and we investigate the utility of this method for two applications in the automotive domain.

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