Study on Integrated Model of SCR-Spar System Affected by Soil Suction

2011 ◽  
Vol 250-253 ◽  
pp. 2807-2813
Author(s):  
Xing Lan Bai ◽  
Ruo Chen Gao
Keyword(s):  
Dynamic Response ◽  
Dynamic Analysis ◽  
Time Domain ◽  
Flexural Rigidity ◽  
Bending Moment ◽  
Computer Code ◽  
Soil Suction ◽  
Steel Catenary Riser ◽  
Coupled Dynamic Analysis ◽  
Analysis Computer

Based on the theory of a slender rod with bending stiffness, Steel Catenary Riser (SCR) is modeled as a small extensible cable. Considering the factors of Spar motion and soil interaction, coupled dynamic analysis for SCR-Spar in time domain is developed using the program developed from a cable dynamic analysis computer code CABLE3D. The paper focuses on the effect of soil suction on dynamic response, tension and bending moment obtained from modified program at key zone of SCR. The results indicate that riser flexural rigidity and soil suction play important roles on affecting the dynamic curvature at the Touch Down Zone (TDZ).

Time-Domain Coupled Dynamic Analysis of Mooring Systems in Extreme Sea Condition

2018 ◽  
Author(s):  
Xuliang Han ◽  
ShiSheng Wang ◽  
Bin Xie ◽  
Wenhui Xie ◽  
Weiwei Zhou
Keyword(s):  
Dynamic Analysis ◽  
Body Surface ◽  
Time Domain ◽  
Mooring Line ◽  
Mooring System ◽  
Dynamic Coupling ◽  
Spar Platform ◽  
Coupled Dynamic Analysis ◽  
Motion Responses ◽  
The Time Domain

In order to predict the coupled motion and external wave load for the design of deepwater floating structure system, based on the three-dimensional time-domain potential flow theory, this paper present the indirect time-domain dynamic coupling method and the body nonlinear dynamic coupling method. The perturbation expansion theory is adopted to evaluate hydrodynamic on the fixed mean wetted body surface for the former method. The transient free surface Green function has been extended and applied to calculate the nonlinear hydrodynamic on the instantaneous wetted exact body surface for the latter method. The finite element model is employed to solve dynamic response of mooring line. Then asynchronous coupled method is adopted to achieve the coupled dynamic analysis of platform and mooring lines. The time-domain motion responses and spectrum analysis of Spar platform are verified and compared with the traditional indirect time-domain coupling dynamic method when the mooring system is completed. Also the time-domain motion responses and statistical characteristic of Spar platform are investigated with one mooring line broken in extreme sea condition. Some conclusions are obtained, that is, dynamic coupling effects are significant and transient position hydrodynamic calculation of platform has a great influence on the low frequency motion. The results also show that the influence on the global performance of mooring system is different when the broken line is in different place. A remarkable influence occurs when the broken mooring line is in the head-wave direction.

Coupled Dynamic Analysis of a Moored Spar Platform in Time Domain

2010 ◽  
Author(s):  
M. D. Yang ◽  
B. Teng
Keyword(s):  
Boundary Condition ◽  
Free Surface ◽  
Dynamic Analysis ◽  
Time Domain ◽  
Surface Boundary ◽  
Spar Platform ◽  
Mooring Lines ◽  
Coupled Dynamic Analysis ◽  
Free Surface Boundary Condition ◽  
Surface Boundary Condition

A time-domain simulation method is developed for the coupled dynamic analysis of a spar platform with mooring lines. For the hydrodynamic loads, a time domain second order method is developed. In this approach, Taylor series expansions are applied to the body surface boundary condition and the free surface boundary condition, and Stokes perturbation procedure is then used to establish corresponding boundary value problems with time-independent boundaries. A higher order boundary element method is developed to calculate the velocity potential of the resulting flow field at each time step. The free-surface boundary condition is satisfied to the second order by 4th order Adams-Bashforth-Moultn method. An artificial damping layer is adopted on the free surface to avoid the wave reflection. For the mooring-line dynamics, a geometrically nonlinear finite element method using isoparametric cable element based on the total Lagrangian formulation is developed. In the coupled dynamic analysis, the motion equation for the hull and dynamic equations for mooring lines are solved simultaneously using Newmark method. Numerical results including motions and tensions in the mooring lines are presented.

Coupled dynamic analysis for wave action on a tension leg-type submerged floating tunnel in time domain

2020 ◽  
Vol 212 ◽  
pp. 107600
Author(s):  
Ruijia Jin ◽  
Ying Gou ◽  
Baolei Geng ◽  
Huaqing Zhang ◽  
Yong Liu
Keyword(s):  
Dynamic Analysis ◽  
Time Domain ◽  
Wave Action ◽  
Coupled Dynamic Analysis ◽  
Submerged Floating Tunnel

Comparison of frequency- and time-domain analyses for guyed masts in turbulent winds

2006 ◽  
Vol 33 (2) ◽  
pp. 169-182 ◽  
Author(s):  
B F Sparling ◽  
L D Wegner
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Dynamic Analysis ◽  
Frequency Domain ◽  
Time Domain ◽  
Element Model ◽  
Mode Shapes ◽  
Nonlinear Behaviour ◽  
Element Analysis ◽  
Guyed Mast

Both frequency- and time-domain methods have been employed in the dynamic analysis of guyed telecommunication masts subjected to turbulent winds. Although the probabilistic frequency-domain approach offers some advantages in terms of its relative ease of implementation and in the statistical reliability of wind load descriptions, the deterministic time-domain method permits a more realistic treatment of system nonlinearities. In this study, a numerical investigation was undertaken to compare frequency- and time-domain dynamic response predictions for a selected guyed mast in gusty winds. Two different analysis techniques were employed, with the frequency-domain calculations performed using response influence lines and the time-domain analyses carried out using a stiffness-based finite element model. Good agreement was observed in root-mean-square and peak dynamic response estimates after compensation was included for differences in turbulence intensity levels assumed in the two models. In general, natural frequencies and mode shapes were also similar.Key words: guyed mast, dynamic analysis, wind, turbulence, nonlinear behaviour, finite element analysis, cables, frequency domain, time domain.

Nonlinear Dynamic Analysis of Jack-Up Platforms Exposed to Extreme Random Waves

2012 ◽  
Author(s):  
Jalal Mirzadehniasar ◽  
Mehrdad Kimiaei ◽  
Mark J. Cassidy
Keyword(s):  
Dynamic Response ◽  
Dynamic Analysis ◽  
Time Domain ◽  
Nonlinear Dynamic ◽  
Spectral Composition ◽  
Random Time ◽  
Offshore Platforms ◽  
Wave Loading ◽  
Nonlinear Dynamic Response ◽  
Jack Up

Deterministic waves with uniquely specified parameters remains widely used in the analysis of offshore platforms, even though the random nature of the sea-state is one of the main uncertainties in loading. The response of dynamically sensitive and highly redundant structures is significantly changed when random wave loading is considered. Therefore, to more confidently simulate wave loads, all of the randomness of water surface should be taken into account. Load history also plays an important role in the nonlinear dynamic response of structures. Accordingly, an appropriate way to consider these effects is dynamic analysis of offshore platforms using random time-domain generation of the sea surface over a long period of time. However, in general, this method is very complex and time consuming. Constrained NewWave theory is an alternative method that can effectively simulate many hours of random time domain simulation for wave loading but in a more computationally efficient manner. It takes a NewWave — a deterministic wave of predetermined height that accounts for the spectral composition of the sea — and constrains it within a random background. In this paper, both the singular NewWave and multiple constrained NewWaves are employed to simulate random sea-states in order to investigate the nonlinear dynamic response and collapse mechanisms of a jack-up platform subjected to extreme waves. Different assumptions of the behavior of the jack-up spudcan-soil interaction are considered.

Dynamic Response Simulation of SCR in TDZ Considering the Soil Property

2012 ◽  
Vol 226-228 ◽  
pp. 1377-1381
Author(s):  
Gan Li ◽  
Xiao Ping Huang
Keyword(s):  
Dynamic Response ◽  
Soil Properties ◽  
Hot Spot ◽  
Bending Moment ◽  
Critical Issue ◽  
Fatigue Analysis ◽  
Stress Variation ◽  
Steel Catenary Riser ◽  
Touchdown Point ◽  
Interaction Problem

The pipe-soil interaction problem is a critical issue in the fatigue analysis of SCR. In this paper, investigation on the initial trench configuration in the touchdown zone (TDZ) of the steel catenary riser (SCR) and factors, which have influence on the trench configuration, such as the amplitude of top end motion were performed firstly. Then the bending moment variation at different points along the trench during the pull up and lay down, the trenches and dynamic response at the touchdown point (TDP) under different soil properties were also investigated. It should be noted that the pipe around the TDZ especially at the TDP, which bears the most drastic bending moment variation and stress variation, is the hot spot in the fatigue analysis of SCR, and the soil properties have big influence on the dynamic stress response amplitude.

Progressive Mooring-Line Failure of a Deepwater MODU in Hurricane Conditions

2009 ◽  
Author(s):  
Zhi Zhang ◽  
M. H. Kim ◽  
E. G. Ward
Keyword(s):  
Time Domain ◽  
Analysis Data ◽  
Field Analysis ◽  
Mooring Line ◽  
Coupled Dynamic Analysis ◽  
Hurricane Ivan ◽  
Analysis Computer ◽  
Drilling Unit ◽  
The Time Domain ◽  
Analysis Computer Program

During 2004–2005, three consecutive category-5 storms hit the central region of Gulf of Mexico (GOM) and damaged numerous drilling and production platforms. Since then, a number of forensic studies have been conducted to better understand the failure causes and mechanism. In this study, a representative deepwater semi-submersible Mobile Offshore Drilling Unit (MODU) that suffered a mooring failure and went adrift during the hurricane Ivan was selected for numerical forensic study. The platform responses and progressive mooring-line failure are simulated in the time domain. A time-domain vessel-mooring coupled dynamic analysis computer program is used to simulate the sequence of progressive mooring-line failure of the MODU in the hindcast Ivan environment, in which the wind, wave, and currents were non-collinear. The case of non-collinear environment is also compared with that of collinear environment. The numerical prediction and simulated results are compared with the available field-analysis data.

Dynamic Analysis of PK Section Girder of Cable Stayed Bridges

2014 ◽  
Vol 638-640 ◽  
pp. 1018-1023
Author(s):  
Li Ying Nie ◽  
Jiang Fei Li ◽  
Zhe Pan
Keyword(s):  
Dynamic Response ◽  
Dynamic Analysis ◽  
Static Load ◽  
Bending Moment ◽  
Element Model ◽  
Internal Force ◽  
Seismic Load ◽  
Negative Bending ◽  
Cable Stayed Bridges ◽  
Load Impact

Pasco-Kennewick (PK) section girder is widely used in the concrete cable stayed bridges with double cable planes, because of its excellent mechanical properties. By created the double girder finite element model, this paper analyzed the dynamic response of one concrete cable stayed bridges with PK section and the dynamic response of the diaphragms. According to the results of the analysis, the diaphragms which near the auxiliaries’ pier s and pylons generated large seismic internal force under the seismic load, and it is account for large proportion when compared with the static load. So, single-girder model can not satisfy the requests for the dynamic analysis of the girder. Due to the cross beams generated large positive, negative bending moment when seismic load impact, we must take notice of strengthening reinforcement in diaphragms. Especially the reinforcement for the negative bending moment, so as to meet the requests for the anti-seismic.

Dynamic Analysis of Mooring Lines for Deep Water Floating Systems

2011 ◽  
Author(s):  
K. Gurumurthy ◽  
Suhail Ahmad ◽  
A. S. Chitrapu
Keyword(s):  
Finite Element ◽  
Dynamic Analysis ◽  
Deep Water ◽  
Time Domain ◽  
Accurate Prediction ◽  
Coupled Analysis ◽  
Analysis Method ◽  
Mooring Lines ◽  
Coupled Dynamic Analysis ◽  
Floating Systems

Efficient dynamic analysis of mooring lines and risers is necessary for deepwater floating systems that typically consist of a number of mooring lines and risers. In deepwater, the interactions between the floater motions and the large number of risers and mooring lines become significant and must be considered for accurate prediction of floater motions as well as line dynamics. Time-domain coupled dynamic analysis procedures have been proposed which can account for the coupling effects and consider most of the nonlinearities present in the problem. These methods have been shown to give more accurate results compared to traditional de-coupled analysis methods although they tend to be computationally more expensive. If the system has a large number of mooring lines and risers, it becomes very difficult and impractical to perform time domain coupled analysis. A number of efficient methodologies have therefore been proposed in the past to balance the accuracy of results with computational efficiency. Such methods include the frequency domain approach, combination of frequency and time domain methods, and combination of coupled and uncoupled analysis methodologies. Enhanced de-coupled dynamic analysis is an efficient method and is similar to the traditional de-coupled dynamic analysis method except that the floater motions are computed by coupled analysis considering a coarse finite element model of the mooring lines. In this paper, dynamic analysis of mooring lines for a deep water classical spar floater under random waves is performed by using the enhanced de-coupled dynamic analysis method and the response statistics are compared with results obtained from coupled dynamic analysis. The spar is modeled as a rigid body with six degrees-of-freedom and the mooring lines are modeled as finite element assemblage of elastic rods. All major non-linearities and the dynamic interaction between spar and its mooring lines are considered while determining the tension time histories. Hinge connection is assumed at the fairleads. At every time step of the integration of equations of motion of the spar, a series of nonlinear dynamic analyses of the mooring lines is performed using a subcycling technique. From the analyses, it is found that the enhanced de-coupled dynamic analysis provides results comparable in accuracy with the results obtained from coupled dynamic analysis in terms of predicting the response statistics, but requires only one third of the computational time. Therefore, enhanced de-coupled dynamic analysis can be used for accurate prediction of mooring line dynamics for deep water floating systems.

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