Dynamic Analysis of an Offshore Platform With Compressor Packages—Application of the Substructure Method

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Ying Zhao ◽  
Xiaohan Jia ◽  
Yian Zhang ◽  
Xueyuan Peng
Keyword(s):  
Dynamic Analysis ◽  
Cutoff Frequency ◽  
Offshore Platform ◽  
Vibration Modes ◽  
Substructure Method ◽  
Free Interface ◽  
Condensation Method ◽  
Fixed Interface ◽  
Mode Truncation ◽  
Fully Coupled

This paper presents the substructure-based dynamic analysis of an offshore platform with compressor packages. Three typical substructure methods, the Guyan condensation method, the fixed-interface component mode synthesis (CMS) method and the free-interface CMS method, were compared to identify the appropriate substructure method for this application. A mode truncation criterion was proposed to ensure the accuracy of the recommended substructure method. The results indicated that the free-interface CMS method could generate almost the same results as the fully coupled method and save more than 50% in calculation time and more than 60% in storage space. When the same amount of time was used, the free-interface CMS method obtained more accurate results than the fixed-interface CMS method and Guyan condensation method; thus, the use of this method for evaluating the dynamics of an offshore platform with compressor packages was recommended. The cutoff frequency of the substructure was suggested to be 1.25 times the highest frequency of interest when conducting a dynamic analysis of an offshore platform with compressor packages using the free-interface CMS method. In addition, the offshore platform is a flexible structure with low and dense mechanical natural frequencies (MNFs), with approximately 4500 orders vibration modes in the frequency range of 0–40 Hz, and the displacement response at the area around the compressor package exceeded the allowable value under the excitation of the compressor package.

A fully coupled particle method for dynamic analysis of saturated soil

2020 ◽  
Author(s):  
J. L. Mroginski ◽  
H. G. Castro ◽  
J. M. Podestá ◽  
P. A. Beneyto ◽  
A. R. Anonis
Keyword(s):  
Dynamic Analysis ◽  
Particle Method ◽  
Saturated Soil ◽  
Fully Coupled

scholarly journals A Multiple and Multi-Level Substructure Method for the Dynamics of Complex Structures

2021 ◽  
Vol 11 (12) ◽  
pp. 5570
Author(s):  
Binbin Wang ◽  
Jingze Liu ◽  
Zhifu Cao ◽  
Dahai Zhang ◽  
Dong Jiang
Keyword(s):  
Structural Characteristics ◽  
Complex Structure ◽  
Complex Structures ◽  
System Matrix ◽  
Substructure Method ◽  
Residual Structure ◽  
The Matrix ◽  
Multi Level ◽  
Fixed Interface ◽  
Selection Of

Based on the fixed interface component mode synthesis, a multiple and multi-level substructure method for the modeling of complex structures is proposed in this paper. Firstly, the residual structure is selected according to the structural characteristics of the assembled complex structure. Secondly, according to the assembly relationship, the parts assembled with the residual structure are divided into a group of substructures, which are named the first-level substructure, the parts assembled with the first-level substructure are divided into a second-level substructure, and consequently the multi-level substructure model is established. Next, the substructures are dynamically condensed and assembled on the boundary of the residual structure. Finally, the substructure system matrix, which is replicated from the matrix of repeated physical geometry, is obtained by preserving the main modes and the constrained modes and the system matrix of the last level of the substructure is assembled to the upper level of the substructure, one level up, until it is assembled in the residual structure. In this paper, an assembly structure with three panels and a gear box is adopted to verify the method by simulation and a rotor is used to experimentally verify the method. The results show that the proposed multiple and multi-level substructure modeling method is not unique to the selection of residual structures, and different classification methods do not affect the calculation accuracy. The selection of 50% external nodes can further improve the analysis efficiency while ensuring the calculation accuracy.

A dynamic condensation method with free interface substructuring

2019 ◽  
Vol 129 ◽  
pp. 218-234 ◽  
Author(s):  
Jeong-Ho Kim ◽  
Seung-Hwan Boo ◽  
Phill-Seung Lee
Keyword(s):  
Free Interface ◽  
Condensation Method ◽  
Dynamic Condensation

Influence of Reference Conditions in the Analysis of the Impact of Flexible Bodies

2001 ◽  
Author(s):  
José L. Escalona ◽  
Juana Mayo ◽  
Jaime Domínguez
Keyword(s):  
Rigid Body ◽  
Reference Conditions ◽  
Normal Modes ◽  
Frame Of Reference ◽  
The Body ◽  
Natural Boundary Condition ◽  
Flexible Bodies ◽  
Free Interface ◽  
Fixed Interface ◽  
The Impact

Abstract In this paper, the floating frame of reference approach is applied to the dynamics of the impact of flexible bodies, while component mode synthesis is used to describe deformation. The influence of the reference conditions, that indicate the type of attachment between the body fixed frame of reference and the flexible bodies, is investigated. Rigid and free attachments allow the use of fixed interface and free interface normal modes, respectively. A finite number of fixed interface modes does not fulfil the natural boundary condition at the attachment point. Free interface normal modes cannot describe the compressive forces at the contact surface. However, it is shown that both set of modes are able to describe the impact-induced elastic waves. In the evaluation of the kinematic coefficient of restitution, these two approaches differ significantly. When free attachment is considered, the derivatives of the reference co-ordinates coincide with the equivalent rigid body velocities of the flexible bodies, remaining constant after the impact. However, if the body frame of reference is rigidly attached, the equivalent rigid body velocities of the flexible body have to be evaluated as a linear combination of the derivative of reference and elastic co-ordinates. The axial impact of a rigid body on a flexible rod and the transverse impact of a flexible pendulum with a fixed stop are simulated to illustrate these facts. Hertzian contact forces are assumed to occur during impact.

Transmitted Power in a Structure Using the Effective Mass Parameters

2010 ◽  
Author(s):  
Costin D. Untaroiu ◽  
Alexandrina Untaroiu ◽  
Matthew Wagner ◽  
Paul E. Allaire
Keyword(s):  
Power Flow ◽  
Complex Structure ◽  
Low Frequency ◽  
Connected Components ◽  
Vibration Modes ◽  
Lumped Mass ◽  
Know How ◽  
Stiffness Matrices ◽  
Lumped Mass Method ◽  
Fixed Interface

To reduce the vibration levels in a complex structure, the designer often needs to know how the vibrations in one part of a structure are transmitted to other parts at each interface of the connected components. A lumped-mass method and component mode synthesis is used to evaluate the power flow for vibrations in low-frequency range. The model mass and stiffness matrices are portioned into substructures separated by the interfaces whose power flow should be evaluated. The vibration modes of the substructure are divided into constrained and fixed interface modes corresponding to the interface and interior degree of freedoms, respectively. The effective interface mass criterion is used to rank the most dynamic important modes at each interface. The most important modes are preserved in a reduced model for computing the power flow. A numerical example of a linear system is used to illustrate the application of the new technique.

Dynamic Analysis of an Integrated Train–Bridge–Foundation–Soil System by the Substructure Method

2018 ◽  
Vol 18 (05) ◽  
pp. 1850069 ◽  
Author(s):  
Hong Qiao ◽  
He Xia ◽  
Xianting Du
Keyword(s):  
Dynamic Analysis ◽  
Shear Velocity ◽  
Rigid Body Dynamics ◽  
Dynamic Responses ◽  
Superposition Method ◽  
Foundation Soil ◽  
Soil System ◽  
Substructure Method ◽  
Soil Foundation ◽  
Bridge Foundation

The substructure method is applied to the dynamic analysis of a train–bridge system considering the soil–structure interaction. With this method, the integrated train–bridge–foundation–soil system is divided into the train–bridge subsystem and the soil–foundation subsystem. Further, the train–bridge subsystem is divided into the train and bridge components. The frequency-dependent impedance function of the soil–foundation subsystem is transformed into time domain by rational approximation and simulated by a high-order lumped-parameter model with masses. The equations of motion of the train and bridge components are established by the rigid-body dynamics method and the modal superposition method, respectively. Finally, the dynamic responses of the two subsystems are obtained by iterative procedures, with the influence of the soil shear velocity studied. The case study reveals that it is important to consider the effect of soil–foundation interaction in the dynamic analysis of train–bridge systems, but with the increase of the shear velocity of the soil, such influence becomes weaker.

Dynamic Analysis of Large Steel Structure Truss System

2011 ◽  
Vol 101-102 ◽  
pp. 387-391
Author(s):  
Chu Qun Wu ◽  
Fan Wang ◽  
Shao Yong Wang
Keyword(s):  
Dynamic Analysis ◽  
Vibration Mode ◽  
Steel Structure ◽  
Vibration Modes ◽  
Finite Element Program ◽  
Large Steel ◽  
Dynamic Computation ◽  
Modes Of Vibration ◽  
Element Program ◽  
Earthquake Vibration

The deformation of the large steel structure truss system, which was subjected to constant loads, variable loads and wind loads, was calculated by using the 3D3S steel structure analysis program. The periods and the vibration mode from the first to the ninth order of the structure were obtained by the earthquake vibration mode period analysis. The dynamic computation of the structure showed that the period difference of the vibration modes is small. The frequencies and the modes of vibration from the first to the ninth order of the same structure mode were calculated by using the ANSYS finite element program. The frequencies and the modes of vibration from the first to the ninth order of the building were obtained by the dynamic analysis of the structure. The dynamic computation of the structure shows that the frequencies difference of the vibration modes is small. The vibration instability is possible for the structure.

scholarly journals The static substructure method for dynamic analysis of structures

1987 ◽  
Vol 20 (4) ◽  
pp. 264-268
Author(s):  
Menglin Lou
Keyword(s):  
Dynamic Response ◽  
Dynamic Analysis ◽  
Static Analysis ◽  
Superposition Method ◽  
Ritz Vector ◽  
Substructure Method ◽  
Large Structures

In this paper, the static substructure method based on the Ritz vector direct superposition method is suggested for analysing the dynamic response of structures. The advantage of this algorithm is that the computer cost can be reduced and the static analysis and the dynamic analysis of large structures can be simplified by using the identical static substructure method.

scholarly journals Grillage Modeling Approach Applied to Simple-span Slab-girder Skewed Bridges for Dynamic Analysis

2018 ◽  
Vol 2 (3) ◽  
pp. 53-65
Author(s):  
Miriam Guadalupe López Chávez ◽  
António Arêde ◽  
José Manuel Jara Guerrero ◽  
Pedro Delgado ◽  
Humberto Varum
Keyword(s):  
Dynamic Analysis ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Modeling Technique ◽  
Computational Time ◽  
Vibration Modes ◽  
Skew Angle ◽  
Skewed Bridges ◽  
Good Ability ◽  
Bridge Model

This study involves the applicability of a simplified modeling technique to simple-span slab-girder skewed bridges for dynamic analysis, based on grillage modeling strategies. To evaluate the applicability of this technique, skew angles ranging from 0° to 60° are studied. The ability to capture vibration modes of grillage models is compared with three-dimensional (3-D) finite element (FE) models, using shell and frame elements. The effect of the skew angle in the grillage modeling technique of the bridge's deck and the grillage model accuracy associated with the orientation of the transverse grillage members (TGMs) are studied. The grillage modeling technique eliminates shell elements to model the slab, reducing the number of degrees of freedom and the computational time in the bridge model, but, although its simplicity, demonstrates good ability to capture the vibration modes.

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