Advanced Dynamic Stability Analysis

2009 ◽  
Author(s):  
Hammam O. Zeitoun ◽  
Knut To̸rnes ◽  
John Li ◽  
Simon Wong ◽  
Ralph Brevet ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Dynamic Response ◽  
Dynamic Stability ◽  
Structural Response ◽  
Force Balance ◽  
Finite Elements Analysis ◽  
Interaction Modelling ◽  
Advanced Analysis ◽  
The Stability ◽  
Subsea Pipelines

Several design approaches can be used to analyse the stability of subsea pipelines [1]. These design approaches vary in complexity and range between simple force-balance calculations to more comprehensive dynamic finite element simulations. The latter may be used to more accurately simulate the dynamic response of subsea pipelines exposed to waves and steady current kinematics, and can be applied to optimise pipeline stabilisation requirements. This paper describes the use of state-of-the-art transient dynamic finite elements analysis techniques to analyse pipeline dynamic response. The described techniques cover the various aspects of dynamic stability analysis, including: • Generation of hydrodynamic forces on subsea pipelines resulting from surface waves or internal waves. • Modelling of pipe-soil interaction. • Modelling of pipeline structural response. The paper discusses the advantages of using dynamic stability analysis for assessing the pipeline response, presents advanced analysis and modelling capabilities which have been applied and compares this to previously published knowledge. Further potential FE applications are also described which extends the applicability of the described model to analyse the pipeline response to a combined buckling and stability problem or to assess the dynamic response of a pipeline on a rough seabed.

Dynamic Stability Response of Piggyback Pipelines

2010 ◽  
Author(s):  
Hammam Zeitoun ◽  
Masˇa Brankovic´ ◽  
Knut To̸rnes ◽  
Simon Wong ◽  
Eve Hollingsworth ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Dynamic Response ◽  
Dynamic Stability ◽  
Large Diameter ◽  
Hydrodynamic Forces ◽  
Model Testing ◽  
Equivalent Diameter ◽  
Pipeline System ◽  
Hydrodynamic Coefficients ◽  
Hydrodynamic Loads

One of the main aspects of subsea pipeline design is ensuring pipeline stability on the seabed under the action of hydrodynamic loads. Hydrodynamic loads acting on Piggyback Pipeline Systems have traditionally been determined by pipeline engineers using an ‘equivalent pipeline diameter’ approach. The approach is simple and assumes that hydrodynamic loads on the Piggyback Pipeline System are equal to the loads on a single pipeline with diameter equal to the projected height of the piggyback bundle (the sum of the large diameter pipeline, small diameter pipeline and gap between the pipelines) [1]. Hydrodynamic coefficients for single pipelines are used in combination with the ‘equivalent diameter pipe’ to determine the hydrodynamic loads on the Piggyback Pipeline System. In order to assess more accurately the dynamic response of a Piggyback Pipeline System, an extensive set of physical model tests has been performed to measure hydrodynamic forces on a Piggyback Pipeline System in combined waves and currents conditions, and to determine in-line and lift force coefficients which can be used in a dynamic stability analysis to generate the hydrodynamic forces on the pipeline [2]. This paper describes the implementation of the model testing results in finite elements dynamic stability analysis and presents a case study where the dynamic response of a Piggyback Pipeline System was assessed using both the conventional ‘equivalent diameter approach’ and the hydrodynamic coefficients determined using model testing. The responses predicted using both approaches were compared and key findings presented in the paper, in terms of adequacy of the equivalent diameter approach, and effect of piggyback gap (separation between the main line and the secondary line) on the response.

scholarly journals Dynamic response of Zelazny Most tailings dam to mining induced extreme seismic event occurred in 2016

2019 ◽  
Vol 262 ◽  
pp. 01001
Author(s):  
Aleksandra Korzec ◽  
Waldemar Świdziński
Keyword(s):  
Stability Analysis ◽  
Dynamic Response ◽  
Dynamic Loading ◽  
Time Integration ◽  
Horizontal Displacement ◽  
Material Model ◽  
Implicit Time ◽  
Tailings Dam ◽  
Peak Horizontal Acceleration ◽  
The Stability

The paper deals with the stability analysis of tailings dam subjected to dynamic loading induced by mining shocks which occurred in neighbouring copper mine. The main goal of the paper was to model the dynamic response of the dam during two extreme paraseismic events which occurred in 2016 based on accelerograms recorded at the dam toe. Dynamic response of the tailings dam was calculated using finite element method and the implicit time-integration method implemented in commercial codes. The boundary condition corresponding to dynamic loading was determined by deconvolution procedure. The error analysis showed that most precise signal reproduction is achieved while using target signal with peak value reduced by 40% as a test signal. Both acceleration and displacement time-series were successfully reproduced. Moreover, the stability analysis was conducted for five independent signals with design peak horizontal acceleration and showed that no permanent displacements should occur. The temporary horizontal displacement of the dam crest should not exceed 13 mm, assuming equivalent linear material model.

scholarly journals Implicit Subspace Iteration to Improve the Stability Analysis in Grinding Processes

2020 ◽  
Vol 10 (22) ◽  
pp. 8203 ◽  
Author(s):  
Jorge Alvarez ◽  
Mikel Zatarain ◽  
David Barrenetxea ◽  
Jose Ignacio Marquinez ◽  
Borja Izquierdo
Keyword(s):  
Stability Analysis ◽  
Dynamic Stability ◽  
Time Domain ◽  
Grinding Processes ◽  
Subspace Iteration ◽  
Efficient Calculation ◽  
Chatter Vibrations ◽  
Stability Maps ◽  
Iteration Methods ◽  
The Stability

An alternative method is devised for calculating dynamic stability maps in cylindrical and centerless infeed grinding processes. The method is based on the application of the Floquet theorem by repeated time integrations. Without the need of building the transition matrix, this is the most efficient calculation in terms of computation effort compared to previously presented time-domain stability analysis methods (semi-discretization or time-domain simulations). In the analyzed cases, subspace iteration has been up to 130 times faster. One of the advantages of these time-domain methods to the detriment of frequency domain ones is that they can analyze the stability of regenerative chatter with the application of variable workpiece speed, a well-known technique to avoid chatter vibrations in grinding processes so the optimal combination of amplitude and frequency can be selected. Subspace iteration methods also deal with this analysis, providing an efficient solution between 27 and 47 times faster than the abovementioned methods. Validation of this method has been carried out by comparing its accuracy with previous published methods such as semi-discretization, frequency and time-domain simulations, obtaining good correlation in the results of the dynamic stability maps and the instability reduction ratio maps due to the application of variable speed.

Dynamic Stability Analysis of the Tower Structure of Construction Elevators

2013 ◽  
Vol 459 ◽  
pp. 646-649
Author(s):  
Xian Rong Qin ◽  
Ying Hong ◽  
Peng Yue ◽  
Qing Zhang ◽  
Yuan Tao Sun
Keyword(s):  
Stability Analysis ◽  
Stress Field ◽  
Dynamic Stability ◽  
Transient Analysis ◽  
Stress Effect ◽  
Construction Process ◽  
Moving Loads ◽  
Eigenvalue Method ◽  
Tower Structure ◽  
The Stability

This paper proposed a method of dynamic stability analysis for the tower structure of construction elevators based on dynamic eigenvalue method. The method employed the time frozen formulation to model the problem, and the stress field from transient analysis was utilized to simulate the pre-stress effect of buckling analysis. The proposed method was applied to estimate the dynamic stability of the tower structure of construction elevators under moving loads, and the results suggest that high coefficients of lateral load and inclined tower structure will dramatically reduce the stability of the elevator in the construction process.

Dynamic Stability Analysis of Defective Piles under Vertical Harmonic Load

2013 ◽  
Vol 477-478 ◽  
pp. 592-595
Author(s):  
Xian Guang Ni
Keyword(s):  
Stability Analysis ◽  
Dynamic Stability ◽  
Critical Frequency ◽  
Harmonic Load ◽  
Heterogeneous Soil ◽  
Engineering Problems ◽  
Practical Engineering ◽  
The Stability ◽  
Dynamical Function

We established the computational mode for defective piles based on practical engineering problems,and studied the stability of the defective pile in the heterogeneous soil under vertical harmonic loads. We established the dynamical function based on the principle of Energy and Hamilton, and abtained the expressions of critical frequency of defective piles.The results show that, the instability of the defective piles relate to the degree of defect and the location of defect.

Effect of Aerodynamic Loads on Dynamic Stability of Slender Launch Vehicle Subjected to an End Rocket Thrust

2002 ◽  
Author(s):  
Tsukasa Ohshima ◽  
Yoshihiko Sugiyama
Keyword(s):  
Stability Analysis ◽  
Dynamic Stability ◽  
Longitudinal Axis ◽  
Launch Vehicle ◽  
Aerodynamic Load ◽  
Aerodynamic Loads ◽  
Eigen Values ◽  
Rocket Thrust ◽  
The Stability ◽  
Free Beam

This paper deals with dynamic stability of a slender launch vehicle subjected to aerodynamic loads and an end rocket thrust. The flight vehicle is simplified into a uniform free-free beam subjected to an end follower thrust. Two types of aerodynamic loads are assumed in the stability analysis. Firstly, it is assumed that two concentrated aerodynamic loads act on the flight body at its nose and tail. Secondly, to take account of effect of unsteady flow due to motion of a flexible flight body, aerodynamic load is estimated by the slender body approximation. Extended Hamilton’s principle is applied to the considered beam for deriving the equation of motion. Application of FEM yields standard eigen-value problem. Dynamic stability of the beam is determined by the sign of the real part of the complex eigen-values. If aerodynamic loads are concentrated loads that act on the flight body at its nose and tail, the flutter thrust decreases by about 10% in comparison with the flutter thrust of free-free beam subjected only to an end follower thrust. If aerodynamic loads are distributed along the longitudinal axis of the flight body, the flutter thrust decreases by about 70% in comparison with the flutter thrust of free-free beam under an end follower thrust. It is found that the flutter thrust is reduced considerably if the aerodynamic loads are taken into account in addition to an end rocket thrust in the stability analysis of slender rocket vehicle.

Tip-Over Stability Analysis of Mobile Boom Cranes With Swinging Payloads

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Andreas Rauch ◽  
William Singhose ◽  
Daichi Fujioka ◽  
Taft Jones
Keyword(s):  
Stability Analysis ◽  
Dynamic Analysis ◽  
Dynamic Stability ◽  
Dynamic Method ◽  
Static Stability ◽  
Multibody Simulation ◽  
The World ◽  
The Stability ◽  
Boom Crane ◽  
Mobile Base

Mobile boom cranes are used throughout the world to perform important and dangerous manipulation tasks. The usefulness of these cranes is greatly improved if they can utilize their mobile base when they lift and transfer a payload. However, crane motion induces payload swing. The tip-over stability is degraded by the payload oscillations. This paper presents a process for conducting a stability analysis of such cranes. As a first step, a static stability analysis is conducted to provide basic insights into the effects of the payload weight and crane configuration. Then, a semi-dynamic method is used to account for payload swing. The results of a full-dynamic stability analysis using a multibody simulation of a boom crane are then compared to the outcomes of the simpler approaches. The comparison reveals that the simple semi-dynamic analysis provides good approximations for the tip-over stability properties. The results of the stability analyses are verified by experiments. The analysis in this paper provides useful guidance for the practical tip-over stability analysis of mobile boom cranes and motivates the need to control payload oscillation.

Effect of Applying 2nd Order Wave Theory on Pipeline Dynamic Response

2010 ◽  
Author(s):  
Hammam Zeitoun ◽  
Knut To̸rnes ◽  
Stuart Oldfield ◽  
Gary Cumming ◽  
Andrew Pearce ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Wave Theory ◽  
Higher Order ◽  
Cost Driver ◽  
Design Solution ◽  
Linear Wave ◽  
Finite Elements Analysis ◽  
Linear Wave Theory ◽  
Wave Kinematics ◽  
Subsea Pipelines

Ensuring subsea pipelines on-bottom stability by determining the stabilisation requirements which will limit pipelines movement under extreme waves and currents is an essential aspect of subsea pipelines design. These requirements can be a major project cost driver in some locations around the world, where the designer is faced with severe metocean conditions. This is particularly the case when the selected design solution is associated with costly stabilisation requirements such as trenching, anchoring [14], rock dumping, or mattressing. An appreciation of the pipeline structural response, when exposed to waves and steady currents kinematics is fundamental to optimise the stabilisation solution. An advanced approach used to optimise stabilisation requirements is to use transient dynamic finite element analysis. The analysis is used to simulate the dynamic response of subsea pipelines exposed to near-seabed kinematics, due to a combination of steady currents and waves. Wave kinematics at the seabed are therefore an essential input to the analysis and will significantly affect both the hydrodynamic loads on the pipeline and the pipeline response. The typical method for generating the wave kinematics in a dynamic analysis has been based on calculating the near-bed velocities corresponding to a randomly generated seastate, using linear wave theory. It has been acknowledged that this calculation is likely to produce a conservative estimate of the positive wave velocities. An improved prediction of seabed kinematics can be achieved by using higher order wave theories. Application of higher order wave theories, results in changing the velocity magnitude under wave crests and troughs. This change in kinematics may result in a change of pipeline response. This paper investigates the effect of using 2nd order wave theory for predicting the kinematics on the pipeline dynamic response. Dynamic finite elements analysis is used for determining the pipeline response and to compare the pipeline response when using 2nd order wave theory and linear wave theory. The work presented in this paper was commissioned by Woodside and performed by J P Kenny Pty Ltd.

Stability Analysis of a Free-Standing Block With Friction on a Moving Foundation

2001 ◽  
Author(s):  
Anna Sinopoli ◽  
Alessio Ageno
Keyword(s):  
Stability Analysis ◽  
Dynamic Response ◽  
Degrees Of Freedom ◽  
A Priori ◽  
Unilateral Constraints ◽  
Free Standing ◽  
Time Intervals ◽  
Analysis And Evaluation ◽  
The Stability ◽  
Scientific Purpose

Abstract The problem analyzed here concerns the dynamic response of a bidimensional polygonal rigid body simply supported on a harmonically moving rigid ground. The immediate scientific purpose of the paper is to obtain and analyze the dynamic response by using a variational formulation, recently proposed by one of the authors [1], where the dynamics is described as a differential inclusion. This formulation allows us to determine the instantaneous accelerations of the system by means of a mechanical model with friction and unilateral constraints, which does not reduce the degrees of freedom or impose an “a priori” choice of the mechanism activated during the motion. By treating the friction coefficient as a stability parameter, it has been possible to obtain different kind of responses, ranging from rocking to sliding-rocking, and compare them with those obtained in the literature. Sliding-rocking motions obtained so far have exhibited not only harmonic but also interesting and more complex behaviors with chaotic features. The search for theoretical and numerical instruments able to identify and classify these more complex motions was first performed in the case of rocking, characterized by a smaller number of degrees of freedom. A technique was then implemented for calculating Lyapunov’s exponents also during the time intervals of the impacts. The introduction and evaluation of these exponents can also permit us to perform the stability analysis with respect to overturning, by limiting the analysis and evaluation to the first impact that the system undergoes by starting at rest: in fact, large values of Lyapunov’s exponents before the first impact are connected with overturning during the motion which follows. This circumstance can make it easier to carry out the stability analysis with respect to overturning, as a function of the amplitude and frequency of the excitation.

Methods for assessing the ship rudder stability under lock-in phenomena considering fluid-structure interactions

2021 ◽  
pp. 147509022110284
Author(s):  
Woen-Sug Choi ◽  
Won-Seok Jang ◽  
Beom-Jin Joe ◽  
Suk-Yoon Hong ◽  
Jee-Hun Song ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Structural Stability ◽  
Structural Response ◽  
Fluid Structure Interactions ◽  
Structural Failure ◽  
Fluid Structure ◽  
Hybrid Coupling ◽  
Structural Responses ◽  
The Stability ◽  
Lock In

Ship rudders, as well as other common underwater appendages, take the form of hydrofoils with a finite trailing-edge thickness to produce wake vortex shedding, which causes vibrations, due to the fluid-structure interactions. Notably, underdetermined phenomena, such as the lock-in phenomenon, raise significant concerns about the structural stability of rudders of large container ships. However, methods to accurately evaluate the stability at the lock-in region are unavailable, because of its high instability, which requires high computational costs, especially for underwater applications. In this study, to address these deficiencies, methods to estimate ship rudders’ structural response and stability at lock-in regions were developed by incorporating hybrid-coupling techniques. The effect of the lock-in phenomenon was investigated using an S-N curve and the fatigue structural-failure probability to quantify the risks. The structural response to the stability analysis was obtained using hybrid-coupling fluid-structure interaction analysis methods by preconditioning the solutions to reduce the numerical instability for first bending and twisting modes with the modified Theodorsen function and to share a single interface between the structure and flow solvers on the OpenFOAM computational fluid dynamics (CFD) toolbox. The accuracy of the structural responses was validated with experiments for the lock-in frequencies, velocity range, and, most importantly, amplitudes of the structural responses of a cantilever hydrofoil. Structural-stability analysis results using the proposed methods demonstrated a significant increase in the probability of premature structural failure, thereby demonstrating the usability of the methods by structural designers in the early design stages.

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