Structural Response Analysis of Tension Leg Platforms

1984 ◽  
Vol 106 (1) ◽  
pp. 10-17 ◽  
Author(s):  
K. Yoshida ◽  
M. Ozaki ◽  
N. Oka
Keyword(s):  
Equations Of Motion ◽  
Structural Response ◽  
Structural Member ◽  
Small Scale ◽  
Response Analysis ◽  
Test Results ◽  
Analysis Method ◽  
Regular Waves ◽  
Response Characteristics ◽  
Structural Responses

A linear response analysis method of the tension leg platform (TLP) subjected to regular waves is proposed. In this analysis method, flexibility of the superstructure can be taken into account in the equations of motion; response motions, tension variations of tendons and structural member forces are solved simultaneously. The applicability of this method is confirmed by comparison with the test results on two kinds of small-scale TLP models. The structural responses obtained from these calculations and their effects on tension variation of tendons are studied. Finally, several kinds of structural response characteristics are conclusively discussed.

Structural Response Analysis of LNG CCS Experiencing the Sloshing Impact Determined by Both Convolution and Fluid Structure Interaction Method

2013 ◽  
Author(s):  
Se Yun Hwang ◽  
Jang Hyun Lee ◽  
Sung Chan Kim ◽  
In Sik Nho ◽  
Beom Seon Jang ◽  
...  
Keyword(s):  
Structural Strength ◽  
Fluid Structure Interaction ◽  
Structural Response ◽  
Computation Time ◽  
Scale Model ◽  
Small Scale ◽  
Response Analysis ◽  
Fluid Structure ◽  
Structure Interaction ◽  
History Of

Sloshing assessment of LNG cargo tanks is expected to satisfy the required structural strength of insulation components. It is difficult to estimate the sloshing pressure and structural response of cargo containment in real size because of the uncertainty of intensive computation time as well as the complexity of sloshing motion. In this study, several procedural components are suggested to meet the endurable strength of LNG CCS during the design of LNG cargo containment. The measured sloshing impacts from small scale model test are treated by individual impacts. Thereafter, static and transient structural response of LNG CCS is sequentially performed in order to evaluate the structural strength. The structural response is also calculated in time series through convolution method considering the history of pressure. It is used to investigate the structural response induced by the history of impacts. Finally, an idealized fluid structure interaction on the localized insulation panel is investigated in order to evaluate the structural strength in actual scale.

scholarly journals Structural Response of Submerged Air-Backed Plates by Experimental and Numerical Analyses

2000 ◽  
Vol 7 (6) ◽  
pp. 333-341 ◽  
Author(s):  
Lloyd Hammond ◽  
Raphael Grzebieta
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Structural Response ◽  
Time History ◽  
Element Model ◽  
Steel Plates ◽  
Small Scale ◽  
History Of ◽  
Structural Responses ◽  
The Finite Element Model

This paper presents the results of a series of small-scale underwater shock experiments that measured the structural responses of submerged, fully clamped, air-backed, steel plates to a range of high explosive charge sizes. The experimental results were subsequently used to validate a series of simulations using the coupled LS-DYNA/USA finite element/boundary element codes. The modelling exercise was complicated by a significant amount of local cavitation occurring in the fluid adjacent to the plate and difficulties in modelling the boundary conditions of the test plates. The finite element model results satisfactorily predicted the displacement-time history of the plate over a range of shock loadings although a less satisfactory correlation was achieved for the peak velocities. It is expected that the predictive capability of the finite element model will be significantly improved once hydrostatic initialisation can be fully utilised with the LS-DYNA/USA software.

VIM Testing of a Paired Column Semi Submersible

2013 ◽  
Author(s):  
Jun Zou ◽  
Philip Poll ◽  
Dominique Roddier ◽  
Nathan Tom ◽  
Antoine Peiffer
Keyword(s):  
Hydrodynamic Interaction ◽  
Slenderness Ratio ◽  
Design Tool ◽  
Small Scale ◽  
Test Results ◽  
Towing Tank ◽  
Response Characteristics ◽  
Reliable Model ◽  
Physical Mechanics ◽  
Difficult Subject

This paper summarizes VIM towing test results of Houston Offshore Engineering’s Paired-Column Semisubmersible (PC Semi) platform that was performed at the UC Berkeley towing tank. The PC semi configuration is different from a conventional Deep Draft Semi (DD Semi) in three aspects, 1) 8 columns vs. 4 columns; 2) rectangle column vs. square column; 3) larger column slenderness ratio. Typically, a larger column slenderness ratio may result in more pronounced VIM. Since VIM significantly affects mooring and riser strength and fatigue, it is crucial to explore the VIM response characteristics of the PC Semi configuration. VIM has been characterized as a difficult subject with a complicated structural-hydrodynamic interaction. The physical mechanics is generally less well understood and numerical prediction is generally less reliable. Model testing has become an important and widely accepted design tool to derive reliable A/D envelops and drag coefficients. This project builds on the VIM testing experiences obtained in Finnigan and Roddier (2007), which showed that VIM testing at small scale is only slightly conservative. A scale factor of 1:160 was used in the present tests. The Reynolds Number for the tests varied from 15,000 to 30,000 depending on the towing speeds. This manuscript provides some details on the test setup and overall program, and highlights the key results of the tests.

A New Procedure for the Nonlinear Structural Response Analysis of Offshore Installations in Explosions

2014 ◽  
Author(s):  
Jeom Kee Paik ◽  
Jerzy Czujko ◽  
Sang Jin Kim ◽  
Jong Chan Lee ◽  
Bong Ju Kim ◽  
...  
Keyword(s):  
Structural Response ◽  
Response Analysis ◽  
Shell Elements ◽  
Nonlinear Structural ◽  
Offshore Installations ◽  
Industry Practice ◽  
Design Values ◽  
Structural Responses ◽  
Explosion Accidents ◽  
Nonlinear Structural Response

This paper is a sequel to the previous two papers by the authors presented at SNAME annual meetings in 2012 and 2013. The key tasks for measuring and managing risks associated with hydrocarbon explosions include defining explosion loads and computing structural responses. In industry practice, such response analysis often involves applying uniformly distributed explosion loads to structures according to their nominal design values. However, uniformly distributed loads based on nominal values of structural design may not always fully reflect the actual situations of real explosion accidents, mainly because the actual characteristics of both explosion loads and structural responses are extremely nonlinear. Therefore, it is highly desirable to identify the non-uniform distributions of explosion loads and directly apply them to structures for the response analysis. To accomplish this, technical challenges must be met in terms of refined computations for loads, structural responses and interfaces between load definitions and structural analyses. This study develops a new procedure to resolve such challenges. In this procedure, FLACS computational fluid dynamics (CFD) simulations are applied to the characterization of blast loads. ANSYS/LS-DYNA nonlinear finite element methods (using plate-shell elements) are applied for nonlinear structural response analysis, and a computer program named FLACS2DYNA is developed to automatize the direct export of the FLACS simulations to the ANSYS/LS-DYNA computations. The contribution of this study is demonstrated through an applied example using a hypothetical topside structure of a VLCC-class FPSO that is exposed to hydrocarbon explosions. This example shows that the developed procedure can enable fast, accurate and reliable nonlinear structural response analysis, and subsequently allow better assessment and management of explosion risks.

Extreme Dynamic Structural Response Analysis of Catenary Moored Spar Wind Turbine in Harsh Environmental Conditions

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Madjid Karimirad ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Fatigue Limit ◽  
Limit State ◽  
Structural Response ◽  
Bending Moment ◽  
Response Analysis ◽  
Ultimate Limit State ◽  
Average Wind Speed ◽  
Structural Responses ◽  
H 20

Proper performance of structures requires among other things that their failure probability is sufficiently small. This would imply design for survival in extreme conditions. The failure of a system can occur when the ultimate strength is exceeded (ultimate limit state (ULS)) or fatigue limit (fatigue limit state) is exhausted. The focus in this paper is on the determination of extreme responses for ULS design checks, considering coupled wave and wind induced motion and structural response in harsh condition up to 14.4 m significant wave height and 49 m/s 10 min average wind speed (at the top of the tower, 90 m) for a parked floating wind turbine of a spar type concept. In the survival condition, the wind induced resonant responses (mainly platform pitch resonance) are dominant. Due to the platform resonant motion responses, the structural responses are close to Gaussian, but wide banded. The critical structural responses are determined by coupled aerohydro-elastic time domain simulation. Based on different simulations (20 1 h, 20 2 h, 20 3 h, and 20 5 h), the mean up-crossing rate has been found in order to predict the extreme structural responses. The most probable maximum of the bending moment and the bending moment having an up-crossing rate of 10−4 are found to be close in the present research. The minimum total simulation time in order to get accurate results is highly correlated with the needed up-crossing rate. The 1 h and 2 h raw data cannot provide any information for 10−4 up-crossing rate. Comparison of different simulation periods shows that the 20 1 h simulations can be used in order to investigate the 3 h extreme bending moment if the proper extrapolation of up-crossing rate is used.

A New Procedure for the Nonlinear Structural Response Analysis of Offshore Installations in Fires

2013 ◽  
Author(s):  
Jeom Kee Paik ◽  
Jerzy Czujko ◽  
Jeong Hwan Kim ◽  
Sung In Park ◽  
Shafiqul Islam ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Thermal Response ◽  
Structural Response ◽  
Fire Risk ◽  
Response Analysis ◽  
Nonlinear Structural ◽  
Offshore Installations ◽  
Fire Loads ◽  
Structural Responses ◽  
Nonlinear Structural Response

The quantitative assessment and management of the risks associated with fire require integrated computations of fire loads and their consequences. The objective of this paper is to present a new procedure for the nonlinear structural response analysis of offshore installations during fires. The procedure comprises calculation of fire loads using computational fluid dynamics (CFD) simulation, thermal response analysis and nonlinear structural response analysis in fire which are key elements in the framework of the fire risk assessment and management. KFX code is used to perform the fire CFD simulation; whereas the analyses of both thermal and nonlinear structural responses are performed using the LS-DYNA code. Models for such analysis can be developed with shell elements to represent the structures with required accuracy. A computer program known as KFX2DYNA is applied to automatically import the results of the KFX simulations which are directly exported to LSDYNA for the analyses of both heat transfer and nonlinear structural responses, making fire risk analysis fast, accurate and reliable. An experimental scenario with a simply supported I-girder under fire is used to validate the procedure. The applicability of the procedure is demonstrated using the example of a fire in the hypothetical topside structure of a VLCC-class FPSO.

scholarly journals Analysis of the Impacts of Bearing on Vibration Characteristics of Rotor

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Peiji Yang ◽  
Qi Yuan ◽  
Chao Huang ◽  
Yafeng Zhou ◽  
Hongliang Li ◽  
...  
Keyword(s):  
Turbine Unit ◽  
Reference Value ◽  
Rotor System ◽  
Response Analysis ◽  
Test Results ◽  
Analysis Method ◽  
Practical Test ◽  
Double Support ◽  
Gas Recovery ◽  
Critical Characteristics

Aiming at a Top Gas Recovery Turbine Unit (TRT) with double support rotor and the extending disk end, theoretical and experimental analysis about influence of cylindrical bearing and four-lobe bearing on vibration of TRT rotor system are conducted in this paper. The results indicate that vibration of the rotor supported by cylindrical bearing is more stable than that supported by four-lobe bearing at the driving end (DE) and the nondriving end (NDE). The amplitude of rotor is supported by both of these types of bearing increases as the speed increases at the NDE, while the amplitude of the DE remains unchanged. Comparing with the result of theoretical analysis, the practical test results are more consistent with the theoretical response analysis conducted by applying unbalanced mass at the extending disk end. This paper presents an analysis method of the critical characteristics of a double support rotor system with the extending disk end and provides reference value for dealing with vibration fault of double support rotor system with the extending disk end.

Structural Response Analysis of Beijing Yin-Tai Center Building under Varying Ground Motions

2011 ◽  
Vol 138-139 ◽  
pp. 217-222
Author(s):  
Fei Wang ◽  
Jie Mei Ma ◽  
Chun Lian Li ◽  
Yun Hui Chen
Keyword(s):  
Seismic Response ◽  
Structural Response ◽  
Time History ◽  
Plastic State ◽  
Response Analysis ◽  
Acceleration Response ◽  
Tangshan Earthquake ◽  
Response Characteristics ◽  
Time Histories ◽  
Contrast Analysis

Deeply studying vibration and seismic response characteristics of Beijing Yin-tai Center provided information reflecting its anti-seismic performance based on which seismic response observation array was to be deployed. Time-historic analytical methods on the basis of modal analysis were applied to carry out structural seismic response. Two load cases were mentioned including the responses under minor earthquakes and moderate earthquakes. El-Centro wave, Northridge wave and synthetized time-histories were adopted with contrast analysis under Beijing Hotel time-history recorded in Tangshan Earthquake. Peak inter-story shift ratios and peak accelerations are obtained and analyzed. The inter-story shift ratio determines elastic state of structure under minor earthquakes and elastic-plastic state under moderate earthquakes. Predominant inter-story displacement and acceleration response provides the floors with more remarkable seismic response, which are vulnerable floors for monitoring in earthquakes.

VIV Response and Fatigue Damage of Flexible Cylinders With Time-Varying Axial Tension

2018 ◽  
Author(s):  
Yuan Yuchao ◽  
Xue Hongxiang ◽  
Tang Wenyong ◽  
Liu Jun
Keyword(s):  
Fatigue Damage ◽  
Structural Response ◽  
Design Stage ◽  
Small Scale ◽  
Time Varying ◽  
Flexible Cylinder ◽  
Time Step ◽  
Response Characteristics ◽  
Axial Tension ◽  
Tension Time

The time-varying effect of axial tension has recently attracted increasing focus when investigating vortex-induced vibration (VIV) for flexible cylinders. This paper applies an alternative time domain force–decomposition model to predict VIV response, in which the structural stiffness will be updated at each time step to take the tension variation into account. Firstly, the adopted numerical model is compared against the latest published experimental results of a small-scale cylinder with constant and time-varying tensions. Then, extensive cases of a long flexible cylinder are designed to investigate the tension time-varying effect on structural response and fatigue damage respectively. Several new response characteristics different from the constant tension case are analyzed from the VIV mechanism level. Fatigue analysis also reveals the influence laws of the amplitude and frequency of varying tension. Mathieu-type resonance between VIV and time-varying tension excitation is captured, under which structural response as well as fatigue damage will enlarge significantly. Some conclusions drawn by this research can provide reference at the engineering design stage of marine slender structures.

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