Nonlinear Wave Load Effects On The Stochastic Behavior Of Fixed Offshore Platforms

1986 ◽  
Author(s):  
J.M. Niedzwecki ◽  
E.W. Sandt
Keyword(s):  
Nonlinear Wave ◽  
Offshore Platforms ◽  
Wave Load ◽  
Stochastic Behavior ◽  
Load Effects

scholarly journals A study on fully nonlinear wave load effects on floating wind turbine

2019 ◽  
Vol 88 ◽  
pp. 216-240 ◽  
Author(s):  
Kun Xu ◽  
Yanlin Shao ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Nonlinear Wave ◽  
Wave Load ◽  
Fully Nonlinear ◽  
Floating Wind Turbine ◽  
Load Effects

Vibration Control of Offshore Platforms Using a Wideband METMD System

2006 ◽  
Author(s):  
Dong Zhao ◽  
Rujian Ma ◽  
Dongmei Cai
Keyword(s):  
Vibration Control ◽  
Natural Frequency ◽  
Fem Simulation ◽  
Average Frequency ◽  
Offshore Platforms ◽  
Frequency Bandwidth ◽  
Wave Load ◽  
Control Effect ◽  
Exciting Frequency ◽  
Specific Frequency

A wideband multiple extended tuned mass dampers (METMD) system has been developed for reducing the multiple resonant responses of the platforms to all kinds of loads, such as earthquake, typhoon, tsunami and big ice load. This system is composed of several subsystems, each of which consists of one set of extended tuned mass damper (ETMD) unit covering a specific frequency bandwidth, and its average frequency is tuned to one of the first resonant frequencies of the platform. The offshore platform is simplified to a single degree-of-freedom (DOF) system to which a METMD subsystem (composed of m ETMDs) is attached and constitutes m+1 DOFs system. The total mass ratio of the METMD subsystem to the platform is 14% and the frequency ratio of the exciting frequency to the platform’s natural frequency varies in [0.5, 1.5]. The theory analysis shows that: 1) the platform has the better vibration control effect when the non-dimensional frequency bandwidth Ω, which is defined as the ratio of the frequency range to the controlled (target) platforms natural frequency, is in [0.35, 0.6]; 2) the damping coefficient ξ of ETMD systems is in [0.05, 0.15] and 3) the number of the ETMDs is 5 when Ω = 0.45 and ξ = 0.1. The FEM simulation shows that the METMD has a better vibration control effect on the mega-platforms’ vibration control under the random ocean wave load.

Combination Factors Suitable for Semi-Probabilistic Design of Floating Production, Storage and Offloading (FPSO) Vessels

2006 ◽  
Author(s):  
Wenbo Huang ◽  
Torgeir Moan
Keyword(s):  
Probabilistic Models ◽  
Probabilistic Design ◽  
Wave Load ◽  
Load Combination ◽  
Load Effects

The paper derived new probabilistic models for still-water loads and the combined still-water and wave load effects of FPSOs. A procedure for determining load combination factors, which is suitable for semi-probabilistic and probabilistic design of FPSOs, is established. The most relevant load combination factors in harsh and benign conditions are derived.

A New Nonslender Ringing Load Approach Verified Against Experiments

1998 ◽  
Vol 120 (1) ◽  
pp. 20-29 ◽  
Author(s):  
J. R. Krokstad ◽  
C. T. Stansberg ◽  
A. Nestega˚rd ◽  
T. Marthinsen
Keyword(s):  
Wave Model ◽  
Second Order ◽  
Wave Load ◽  
Peak Wavelength ◽  
Third Order ◽  
Load Model ◽  
Order Analysis ◽  
First Order ◽  
Load Effects ◽  
Vertical Cylinders

New results from the most recent work within the Norwegian Joint Industry Project (JIP) “Higher Order Wave Load Effects on Large Volume Structures” are presented. A nonslender theoretical model is validated from experiments for two fixed, vertical cylinders with different diameter/peak wavelength ratios. A combination of complete diffraction first-order simulations, sum and difference frequency second-order simulations, and third-order FNV (Faltinsen, Newman, and Vinje, nonlinear long wave model) is implemented in order to develop a simplified and robust ringing load model for a large range of cylinder diameter/peak wavelength ratios. Results from the full diffraction second-order analysis show a significant reduction of second-order loads compared to pure FNV in the wavelength range relevant for ringing loads. The results show improved correspondence with high-frequency experimental loads compared with the unmodified FNV. Results for different cylinder peak wavelength ratios are presented, including validation against experiments. In addition, a few simplified response simulations are carried out demonstrating significant improvements with the modified FNV model.

Nonlinear Effects on Long-Term Distributions of Wave-Induced Loads for Tankers

1998 ◽  
Vol 120 (2) ◽  
pp. 65-70 ◽  
Author(s):  
C. Guedes Soares ◽  
T. E. Schellin
Keyword(s):  
Nonlinear Wave ◽  
Nonlinear Effect ◽  
Nonlinear Effects ◽  
Vertical Load ◽  
Load Effects ◽  
Wave Induced

A method of long-term formulation of the nonlinear wave-induced vertical load effects on ships was applied to three tanker hulls of different sizes. For large tanker hulls, the nonlinear effect is not significant, and thus linear theories can continue to be used for earlier studies on these kind of ships, contrary to what was shown earlier for containership hulls. However, for smaller tankers, significant nonlinear values were obtained, with both sagging and hogging nonlinear results being larger than the linear ones.

Efficient Evaluation of Long-Term Response for Design of Components of Offshore Structures

2017 ◽  
Author(s):  
Paulo Mauricio Videiro ◽  
Luis Volnei Sudati Sagrilo
Keyword(s):  
Limit State ◽  
Offshore Structures ◽  
Ultimate Limit State ◽  
Wave Load ◽  
Wave Effects ◽  
Load Effects ◽  
Bracing System ◽  
Term Response ◽  
Tubular Component

This paper compares two approaches for the estimation of long-term response of wave load effects on offshore structures. These approaches are applied to estimate the extreme value of the cross section interaction ratio of a tubular component of the bracing system of a semisubmersible platform. The tubular component is subjected to axial loads and bending moments due to static loads and wave effects. The iteration ratio in the ultimate limit state is defined by applying design criteria derived from API RP-2A LRFD [6]. The approaches are also applied to estimate the long-term response of a single degree of freedom system due to wave actions. The first approach is based on the proposals of Videiro and Moan [3]. The results of the first approach are compared with a new model of long-term response estimation, based on the up-crossing rate distribution of the response process.

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