An Efficient Time Domain Code for Strength and Fatigue Analysis of Steel Catenary Risers

2015 ◽  
Author(s):  
Djoni E. Sidarta ◽  
Xiaoning Jing ◽  
Kostas F. Lambrakos ◽  
Roger W. Burke ◽  
William C. Webster
Keyword(s):  
Time Series ◽  
Finite Element ◽  
Dynamic Analysis ◽  
Time Domain ◽  
Fatigue Analysis ◽  
Strength Analysis ◽  
Analysis Software ◽  
Finite Element Program ◽  
Element Program ◽  
Steel Catenary Risers

Steel Catenary Risers (SCRs) are commonly used in the offshore industry. Strength and fatigue performance of SCRs due to waves, currents and vessel motions is typically calculated using time domain dynamic analysis. Strength analysis may involve a large number of load cases for different environments, riser conditions and vessel configurations. Fatigue analysis may involve computation of riser response for hundreds of fatigue sea-states. It is very important for project schedule and cost that the analysis software used is both accurate and computer efficient. This paper presents RodDyn as an alternative time domain analysis tool for SCR strength and fatigue analysis. RodDyn is a finite element program for dynamic analysis of single-pipe risers. Several publications on this program are available in the literature. The results of dynamic analysis of an SCR for strength and fatigue from RodDyn are compared against the results from ABAQUS. ABAQUS is a general finite element program that has been widely used in the offshore exploration and production industry and has been considered one of the standard finite element programs. Riser dynamic analysis uses time series of vessel motions due to metocean environments at an oblique angle to the plane of the SCR. Von Mises stress per API RP 2RD, strength checks per API STD 2RD and fatigue damage along the riser are presented for both RodDyn and ABAQUS. Time series of effective tension and bending moments at selected locations on the riser are also compared. The main advantage of using RodDyn for riser analysis is the speed of computation. This paper shows that RodDyn can deliver significant gains in computational speed compared to standard riser analysis software programs without sacrificing accuracy of the computed results.

Analysis of Impeller Vibration in Radial Compressors

1986 ◽  
Author(s):  
J. Wachter
Keyword(s):  
Finite Element ◽  
Dynamic Analysis ◽  
Modal Analysis ◽  
Dynamic Behaviour ◽  
Modal Parameters ◽  
Centrifugal Impeller ◽  
Experimental Investigations ◽  
Finite Element Program ◽  
Element Program ◽  
Detailed Application

The prediction of the dynamic behaviour of the impellers is of considerable importance in the design of turbomachines. The excitation possibilities of the radial impellers by the forces or imposed displacements are various and an appreciation of the life of radial impellers is strongly bounded to an accurate dynamic analysis. Therefore, it is necessary to analyze them in order to improve the geometry or modify the design. In order to better understand and explain the dynamic behaviour of impellers, a series of impeller models with various numbers of blades of radial or tangential extention have been examined. Because of complexity of analytical analysis shown in earlier works, the eigenfrequencies and modes of the impellers were evaluated using a Finite Element program. Interferometric holography served as a means to visualize the dynamic behaviour of the impellers. An experimental modal analysis was used to identify the modal parameters. A detailed application of these methods to an actual centrifugal impeller was also reported along with theoretical and experimental investigations on the impeller models.

New Design Configuration of Steel Catenary Risers With Pull-Tube for Spars

2011 ◽  
Author(s):  
Shan Shi ◽  
Charlie Mao ◽  
Jenny Yang ◽  
Nishu Kurup
Keyword(s):  
Finite Element ◽  
Finite Element Program ◽  
Additional Advantage ◽  
Nonlinear Contact ◽  
Element Program ◽  
Steel Catenary Risers ◽  
Bending Loads ◽  
A Current ◽  
Water Depths ◽  
Over Time

In previous Spar designs where pull tubes were used to board the risers (either export or flowline risers), the pull-tube extended a considerable distance beyond the keel and used a tapered design to form a bend restrictor that supported the riser throughout the riser/hull interface. In a current Spar design, the pull-tube is terminated at the hull keel and the bending loads are carried by a double sided stress-joint in the riser that pivots on a centralizer located near the bottom of the pull-tube. Essentially, this is an adaptation of the double-sided stress joint used for top tensioned risers exiting the bottom of their buoyancy can stems to the similar condition of an SCR exiting a pull tube terminating at the Spar’s keel. This new pull-tube and SCR configuration can be applied for both Truss and Classic Spars. SCRs boarding Spars through pull tubes have several advantages over stress joints or flex-joints anchored in porches, notably, eliminating both the need for divers to make large piping connections at 500′ to 600′ water depths and the possibility of those connections leaking over time. Moving the bend restrictor function from the pull tube to the riser provides the additional advantage of adding flexibility for the Spar to accommodate future risers whose size and weight are not known at the time the pull tubes are designed and the platform is installed. With the stress joint as part of the riser, the bend restrictor can be custom designed for each riser since the pull tube works the same for all risers. The SCR and stress joint, pull-in and in-place analyses have been performed by using the finite element program ABAQUS. The nonlinear capabilities of ABAQUS including the hybrid, gap and contact element formulations are utilized in the analysis of the pull-in process. The nonlinear contact elements with finite sliding capability are modeled with an exponential over-closure relationship.

Piezoelectric modelling using a time domain finite element program

2007 ◽  
Vol 27 (13-15) ◽  
pp. 4153-4157 ◽  
Author(s):  
Yago Gómez-Ullate Ricón ◽  
Francisco Montero de Espinosa Freijo
Keyword(s):  
Finite Element ◽  
Time Domain ◽  
Finite Element Program ◽  
Element Program

scholarly journals Silent Boundary Scheme and Analysis of Existing Methods of providing Silent Boundary

2020 ◽  
Vol 12 (01) ◽  
Author(s):  
Jyoti Agarwal ◽  
Ankush Chaudhary
Keyword(s):  
Finite Element ◽  
Kinetic Energy ◽  
Dynamic Analysis ◽  
Strain Energy ◽  
Vertical Displacement ◽  
Boundary Effects ◽  
Simple Problem ◽  
Two Dimensional ◽  
Finite Element Program ◽  
Element Program

For dynamic analysis, it is required to provide viscous boundaries in PLAXIS to reduce the boundary effects and to prevent the reflection of waves from boundaries. So, a study has been carried out to compare the various methods of providing silent boundaries and to see the effectiveness of viscous boundaries used in PLAXIS. In this work, three methods of providing silent boundaries, which are viscous boundaries, local damping, and extended boundary, are analyzed using a 2D finite element program in FORTRAN by considering the simple problem of a two-dimensional vertical bar. Parameters, such as, normal stress at the bottom, vertical displacement at the top, potential energy, kinetic energy, strain energy, and total energy of bar are determined with and without using the above three methods of providing silent boundaries. Results are compared using graphs. It was observed that standard viscous boundaries are not much effective for static analysis but most effective for dynamic analysis.

Development of Offshore Structural Analysis Software X-SEA Coupled With FAST

2019 ◽  
Author(s):  
Ki-Du Kim ◽  
Sorrasak Vachirapanyakun ◽  
Pasin Plodpradit ◽  
Van Nguyen Dinh ◽  
Jin-Ho Park
Keyword(s):  
Finite Element ◽  
Offshore Structures ◽  
Theoretical Background ◽  
Imperial College ◽  
Coupled Analysis ◽  
Current Version ◽  
Analysis Software ◽  
Element Analysis ◽  
Finite Element Program ◽  
Element Program

Abstract Coupled analysis of offshore structures is currently challenging. The 3D finite element analysis software X-SEA coupled with FAST 8 program is therefore developed and discussed in this paper. The current version of X-SEA includes the results of extensive research and development based on finite element program XFINAS, which was originally developed in Imperial College London. The solution of the X-SEA ranges from the simple static to highly advanced dynamic analysis applied to the offshore structures. GID is used as pre- and post processor of X-SEA. The brief theoretical background of X-SEA software is summarized. Numerical examples of offshore monopile, wind turbine jackets, pile super element and fatigue analysis verified with SACS software in terms of reactions, displacements and member forces are investigated.

Analysis of Dynamic Performance of Air-Cooled Condenser Structure System

2012 ◽  
Vol 170-173 ◽  
pp. 2675-2680
Author(s):  
Ying Sun ◽  
Yan Hong
Keyword(s):  
Finite Element ◽  
Time Domain ◽  
Power Plants ◽  
Vibration Mode ◽  
Dynamic Performance ◽  
Cycle Frequency ◽  
Finite Element Program ◽  
Structure System ◽  
Element Program

In situ measurements on two power plants designed air-cooled condenser structure were described in this paper. Operating condition was divided into three types to test the structure system, and then obtaining the data of time-domain waveform and spectrum analysis in each condition. Cycle, frequency and vibration mode of the structure system were obtained by analyzing the data. Meanwhile, the structure was theoretically calculated using finite element program, gaining the cycle, frequency and vibration mode of the structure system. It was concluded that basic vibration mode of the structure system was space torsional vibration by comparison between theoretical values and measured values.

scholarly journals The impact of drilling and slitting construction on damage field: evolution characteristics in low-permeability coal seam

2021 ◽  
Vol 37 ◽  
pp. 205-215
Author(s):  
Heng Chen ◽  
Hongmei Cheng ◽  
Aibin Xu ◽  
Yi Xue ◽  
Weihong Peng
Keyword(s):  
Finite Element ◽  
Rock Mass ◽  
Damage Mechanics ◽  
Effective Strain ◽  
Secondary Development ◽  
Distribution Area ◽  
Finite Element Program ◽  
Element Program ◽  
Mining Face ◽  
The Impact

ABSTRACT The fracture field of coal and rock mass is the main channel for gas migration and accumulation. Exploring the evolution law of fracture field of coal and rock mass under the condition of drilling and slitting construction has important theoretical significance for guiding efficient gas drainage. The generation and evolution process of coal and rock fissures is also the development and accumulation process of its damage. Therefore, based on damage mechanics and finite element theory, the mathematical model is established. The damage variable of coal mass is defined by effective strain, the elastoplastic damage constitutive equation is established and the secondary development of finite element program is completed by FORTRAN language. Using this program, the numerical simulation of drilling and slitting construction of the 15-14120 mining face of Pingdingshan No. 8 Mine is carried out, and the effects of different single borehole diameters, different kerf widths and different kerf heights on the distribution area of surrounding coal fracture field and the degree of damage are studied quantitatively. These provide a theoretical basis for the reasonable determination of the slitting and drilling arrangement parameters at the engineering site.

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