Coupled Motion Analysis of a Semisubmersible Platform in Campos Basin

2004 ◽  
Author(s):  
Francisco Edward Roveri ◽  
Marcos Vinicius Rodrigues ◽  
Breno Pinheiro Jacob
Keyword(s):  
Numerical Models ◽  
Nonlinear Dynamic Analysis ◽  
Coupled Analysis ◽  
Current Profile ◽  
Time Step ◽  
Frequency Spectra ◽  
Environmental Loading ◽  
Campos Basin ◽  
Loading Case ◽  
Platform Motions

This work describes the generation of numerical models for the coupled analysis of a semisubmersible platform to be installed in Campos Basin, and presents the results, in terms of platform motions, of a set of analyses under fatigue environmental loading cases. The coupled model comprises the hull, the mooring lines, and all risers connected to the platform. The model includes also a FSHR (Free Standing Hybrid Riser) system to be connected to the platform; this system is composed by a rigid riser, an air can and a flexible jumper. A set of environmental loading cases appropriate for fatigue analyses is defined, in terms of current profile, irregular bi-directional seastate, and wind. For each loading case, nonlinear time-domain dynamic analyses are performed employing the Prosim program. This program is based in a coupled formulation that incorporates, in a single code and data structure, a hydrodynamic model to represent the hull, and a finite element model to rigorously represent the structural/hydrodynamic behavior of the lines. At every time step of the time integration of the equations of motion representing the hull, a series of nonlinear dynamic analysis of the lines is performed following a subcycling procedure. The results of the coupled analysis are expressed as time histories of platform motions. The next step is to proceed to the treatment of these time series, in order to determine, for each loading case: a) The frequency spectra of each motion component; and b) Representative statistical values in terms of static offsets, first and second-order motions (standard deviations and periods for low-frequency and wave-frequency motions). The platform motions that result from the coupled analyses presented in this work can be employed to perform the detailed structural analysis of the FSHR system, by employing an isolated model of the riser in a specialized program.

Masonry Spires: 3D Models to Understand their Seismic Vulnerability

2019 ◽  
Vol 817 ◽  
pp. 317-324
Author(s):  
Elena Zanazzi ◽  
Eva Coïsson ◽  
Daniele Ferretti ◽  
Alessio Lorenzelli
Keyword(s):  
Dynamic Analysis ◽  
Seismic Vulnerability ◽  
Linear Time ◽  
Numerical Models ◽  
Nonlinear Dynamic Analysis ◽  
Nonlinear Static Analysis ◽  
Time Step ◽  
Epicentral Area ◽  
Finite Element Software ◽  
Bell Tower

The May 2012 Emilia earthquake has highlighted the important vulnerability of masonry spires at the top of bell towers of churches. Indeed, almost half of those in the epicentral area have shown a typical damage mechanism consisting in the shear sliding and overturning of the top of the spire. Given the recurrence of this phenomenon, the present paper tries to provide a contribution to the comprehension of the seismic behaviour of the spires through the numerical analysis of three case studies. In particular, the work analyses the spires of the churches of San Nicola di Bari in Cortile, near Carpi (MO); Sant'Egidio in Cavezzo (MO), and Sant'Agostino in Sant'Agostino (FE). The numerical models of these masonry structures were made using Abaqus Finite Element software. After the creation of the three-dimensional geometric models, a first nonlinear static analysis of the entire bell tower was performed adopting for masonry the Abaqus “concrete damage plasticity model”. Once the stability of the bell tower was verified for dead loads, the non-linear time-step dynamic analysis was faced. This required the definition of the seismic input at the base of the tower, through the accelerograms recorded by the closest stations. The nonlinear dynamic analysis of the global model of the bell tower provided the floor response spectra at the base and at the top of the spire. Indeed the comparison between spectra at the ground and at the top highlights the filter effect of the stem of the bell tower with a significant increase in accelerations at the top. This effect may explain the widespread damage observed at the top of the spires. Eventually, three different non-invasive intervention techniques were proposed in compliance with the principles of restoration and were modelled to compare their behaviour.

Comportement dynamique des lignes aériennes de transport d'électricité dû aux bris de câbles. II. Problèmes numériques associés à la modélisation mathématique

1989 ◽  
Vol 16 (3) ◽  
pp. 354-374 ◽  
Author(s):  
Ghyslaine McClure ◽  
René Tinawi
Keyword(s):  
Transmission Lines ◽  
Nonlinear Dynamic ◽  
Numerical Models ◽  
Equations Of Motion ◽  
Nonlinear Dynamic Analysis ◽  
Small Scale ◽  
Convergence Criterion ◽  
Direct Integration ◽  
Time Step ◽  
Integration Methods

The evaluation of the response of an aerial power line section subjected to cable breakage is a complex dynamic problem in which geometric nonlinearities are important. The solution of the equations of motion of the model calls for direct integration methods for which the stability and behavior, in nonlinear situations, are difficult to predict. Seven numerical models are analyzed with the Wilson-θ and the Newmark-β algorithms and results are compared with those of small-scale tests of the American Electric Power Research Institute. This comparison emphasizes the importance of the high frequency modes in the response and the artificial damping induced by the Wilson-θ method. This method allows up to three times the time increment required by the trapezoidal rule that does not filter the contribution of higher frequencies but is limited by a convergence criterion. Many observations made in this particular study are also applicable to multi-degree-of-freedom nonlinear dynamic problems using direct time-step integration. Key words: Nonlinear dynamic analysis, direct integration methods, aerial electric transmission lines, cable breakage simulation.

scholarly journals Wavelet-based Decomposition of Ground Acceleration for Efficient Calculation of Seismic Response in Elastoplastic Structures

2020 ◽  
Author(s):  
Reza Kamgar ◽  
Noorollah Majidi ◽  
Ali Heidari
Keyword(s):  
Wavelet Transform ◽  
Dynamic Analysis ◽  
Continuous Wavelet Transform ◽  
Nonlinear Dynamic ◽  
Nonlinear Dynamic Analysis ◽  
Continuous Wavelet ◽  
Frequency Content ◽  
Time Step ◽  
Integration Schemes ◽  
The Waves

The nonlinear dynamic analysis provides a more accurate simulation of the structural behavior against earthquakes. On the other hand, this analysis method is time-consuming since the time-step integration schemes are used to calculate the responses of the structure. Wavelet transform is also considered as one of the strong computing tools in studying the properties of the waves. The continuous wavelet transform is a time-frequency study and examines the frequency content of the waves while, the discrete wavelet transform is used to reduce sampling data and also to eliminate the noise of the waves. In this paper, the discrete and continuous wavelet transforms are used to reduce the wave sampling and therefore to reduce the required time for analysis. In this regard, eight near- and far- field earthquakes are studied. The frequency content of the earthquake is investigated by the Fourier spectrum and the continuous wavelet transform. The results show that the first five frequencies for the main earthquakes are similar to those values of earthquakes obtained by wavelet transform. Besides, it is shown that using wavelet transform for the main and decomposed earthquakes indicates that the duration of strong ground motion and the time of dominant frequency occur approximately in the same domain. Finally, it is concluded that the required calculation time reduces to about 80 % with an error less than 6 % when the main earthquake is decomposed by wavelet transform and the approximation waves are used in the nonlinear dynamic analysis.

Geometric Nonlinear Dynamic Analysis of Tapered Steel Members

2020 ◽  
Author(s):  
Yasir F. Al-Lebban
Keyword(s):  
Dynamic Analysis ◽  
Mass Matrix ◽  
Nonlinear Dynamic Analysis ◽  
Axial Deformation ◽  
Step Size ◽  
Time Step ◽  
Time Step Size ◽  
Geometric Nonlinear ◽  
Steel Members ◽  
Mass Matrices

In this study, a theoretical analysis is presented for estimating the in-plane geometric nonlinear elastic stability behavior of steel members with tapered elements under dynamic loads. Beam-column approach is adopted for modeling the structural members as beam-column elements. The formulation is based on the Eulerian description taking into consideration the influence of axial force on bending stiffness. The changes in member chord length due to axial deformation and flexural bowing are also considered. In the dynamic analysis, the system mass properties have been represented using both lumped and consistent mass matrices. The consistent mass matrix is derived in three components: translational, rotational, and axial inertia. The formulation of the mass matrices in local and global coordinate systems of tapered members, which incorporates geometric nonlinearity, has been presented. A parametric study is conducted to examine the effects of number of tapered elements, tapering the prismatic members, time step size, and tapering ratio.

An Efficient Non-Iterative Hybrid Method for Analyzing Train–Rail–Bridge Interaction Problems

2020 ◽  
pp. 2150029
Author(s):  
Kang Shi ◽  
Xuhui He ◽  
Yunfeng Zou ◽  
Zhi Zheng
Keyword(s):  
Hybrid Method ◽  
Computational Efficiency ◽  
High Speed ◽  
Low Frequency ◽  
Coupled Analysis ◽  
Time Step ◽  
Coupling Vibration ◽  
Current Time ◽  
Railway Bridges ◽  
Frequency Coupling

The dynamic interaction problem for the train–rail–bridge (TRB) systems presents a computational challenge, especially for the analysis of large-size TRB coupling systems. To address this issue, an efficient non-iterative hybrid method (NHM) is proposed. With this method, the integrated TRB system is divided into three subsystems, i.e. the train subsystem, the rail subsystem, and the bridge subsystem. Based on the individual subsystems, a multi-step[Formula: see text] technique is adopted in which a fine time step is used to analyze the high-frequency coupling vibration for the train and rail subsystems, and a coarse time step is adopted to calculate the low-frequency coupling vibration for the rail and bridge subsystem. Additionally, Zhais explicit integral method is used to predict the displacement of the wheelsets and the rail at the current time step before using the Newmark method. The proposed method incorporates the advantages of Zhai’s explicit method and the MS technique to avoid the iteration that may be required for the train–rail coupled analysis. The simulation fidelity and computational efficiency of the proposed method are demonstrated in the analysis of two examples of typical high-speed railway bridges. It was demonstrated that the proposed method can significantly enhance the computational efficiency, while maintaining a higher precision with a larger time step in comparison with other existing methods.

Development and Preliminary Verification of a Thermal-Hydraulic Multi-Scale Coupled Code

2010 ◽  
Author(s):  
Yu Liu ◽  
Hong Zhang ◽  
Baoshan Jia
Keyword(s):  
Nuclear Power ◽  
Data Exchange ◽  
External Control ◽  
Coupled Analysis ◽  
Time Step ◽  
Multi Scale ◽  
Coupling Strategy ◽  
Computational Fluid Dynamics Cfd ◽  
Integral Structure ◽  
Future Work

On the basis of best estimate thermal-hydraulic system code RELAP5, sub-channel code COBRA-1V, and commercial Computational Fluid Dynamics (CFD) code CFX, a thermalhydraulic multi-scale coupled code RECOX has been developed. The coupling strategy was designed to keep the integral structure of each code and minimize modifications of code source. Under the Parallel Virtual Machine (PVM) environment, an external control code has been developed to perform codes spawn, data exchange and mapping, time step coordination, etc. Two test cases including single phase blowdown and temperature fluctuation transient have been carried out to evaluate the coupling between codes. Compared with stand-alone simulations very good agreement was achieved. Then in order to demonstrate the coupled analysis capability of RECOX, an asymmetry transient in a simple two loops system which is similar to the nuclear power plant was simulated. The result is correct and reliable, although further verification of coupled code with related experiment is needed. Finally, some potential improvements of coupling and future work were presented.

A RANS numerical model for cross-shore beach profile evolution

2020 ◽  
Author(s):  
Julio Garcia-Maribona ◽  
Javier L. Lara ◽  
Maria Maza ◽  
Iñigo J. Losada
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Transport Model ◽  
Numerical Models ◽  
Computational Cost ◽  
Physical Modelling ◽  
Computational Effort ◽  
Beach Profile ◽  
Time Step ◽  
Wave Conditions

<p>The evolution of the cross-shore beach profile is tightly related to the evolution of the coastline in both small and large time scales. Bathymetry changes in extreme maritime events can also have important effects on coastal infrastructures such as geotechnical failures of foundations or the modification of the incident wave conditions towards a more unfavourable situation.</p><p>The available strategies to study the evolution of beach profiles can be classified in analytical, physical and numerical modelling. Analytical solutions are fast, but too simplistic for many applications. Physical modelling provides trustworthy results and can be applied to a wide variety of configurations, however, they are costly and time-consuming compared to analytical strategies. Finally,  numerical approaches offer different balances between cost and precision depending on the particular model.</p><p>Some numerical models provide greater precision in the beach profile evolution, but incurring in a prohibitive computational cost for many applications. In contrast, the less expensive ones assume simplifications which do not allow to correctly reproduce significant phenomena of the near-shore hydrodynamics such as wave breaking or undertow currents, neither to predict important features of the beach profile like breaker bars.</p><p>In this work, a new numerical model is developed to reproduce the main features of the beach profile and hydrodynamics while maintaining an affordable computational cost. In addition, it is intended to reduce to the minimum the number of coefficients that the user has to provide to make the model more predictive.</p><p>The model consists of two main modules. Firstly, the already existing 2D RANS numerical model IH2VOF is used to compute the hydrodynamics. Secondly, the sediment transport model modifies the bathymetry according to the obtained hydrodynamics. The new bathymetry is then considered in the hydrodynamic model to account for it in the next time step.</p><p>The sediment transport module considers bedload and suspended transports separately. The former is obtained with empirical formulae. In the later,the distribution of sediment concentration in the domain is obtained by solving an advective-diffusive transport equation. Then, the sedimentation and erosion rates are obtained along the seabed.<br>Once these contributions are calculated, a sediment balance is performed in every seabed segment to determine the variation in its level.</p><p>With the previously described strategy, the resulting model is able to predict not only the seabed changes due to different wave conditions, but also the influence of this new bathymetry in the hydrodynamics, capturing features such as the generation of a breaker bar, displacement of the breaking point or variation of the run-up over the beach profile. To validate the model, the numerical results are compared to experimental data.</p><p>An important novelty of the present model is the computational effort required to perform the simulations, which is significantly smaller than the one associated to existing models able to reproduce the same phenomena.</p>

scholarly journals Development of a Numerical Model for an Expanding Tube with Linear Explosive Using AUTODYN

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Mijin Choi ◽  
Jung-Ryul Lee ◽  
Cheol-Won Kong
Keyword(s):  
Numerical Model ◽  
Numerical Models ◽  
Nonlinear Dynamic Analysis ◽  
Economic Benefits ◽  
Steel Tube ◽  
Test Results ◽  
Ballistic Test ◽  
Satellite Launch Vehicle ◽  
Joint Separation ◽  
2D And 3D

Pyrotechnic devices have been employed in satellite launch vehicle missions, generally for the separation of structural subsystems such as stage and satellite separation. Expanding tubes are linear explosives enclosed by an oval steel tube and have been widely used for pyrotechnic joint separation systems. A numerical model is proposed for the prediction of the proper load of an expanding tube using a nonlinear dynamic analysis code, AUTODYN 2D and 3D. To compute a proper core load, numerical models of the open-ended steel tube and mild detonating tube encasing a high explosive were developed and compared with experimental results. 2D and 3D computational results showed good correlation with ballistic test results. The model will provide more flexibility in expanding tube design, leading to economic benefits in the overall expanding tube development procedure.

Towards the Integration of Analysis and Design of Mooring Systems and Risers: Part I — Studies on a Semisubmersible Platform

2002 ◽  
Author(s):  
Stael Ferreira Senra ◽  
Fabricio Nogueira Correa ◽  
Breno Pinheiro Jacob ◽  
Ma´rcio Martins Mourelle ◽  
Isai´as Quaresma Masetti
Keyword(s):  
Motion Analysis ◽  
Production Systems ◽  
Companion Paper ◽  
Coupled Analysis ◽  
Mooring Line ◽  
Mooring System ◽  
Analysis And Design ◽  
Design Methodologies ◽  
Campos Basin ◽  
Fully Coupled

The objective of this paper is to study different analysis methodologies for the design of floating production systems. The main issues are the use of uncoupled and coupled analysis methods, and the integration in the analysis and design of the mooring system and the risers. This paper is a companion to another paper also presented in the OMAE2002 Conference [1] The present paper begins describing a “basic” classic, uncoupled methodology, and proceeds with comments on some refinements in the representation of the behavior of the lines in the motion analysis of the vessel. Comments regarding the introduction of some level of integration between mooring line and riser behavior are also presented. These issues are illustrated with studies applying some of the considered design methodologies to the P-18 semi-submersible platform in Campos basin. The companion paper [1] proceeds describing a fully coupled methodology, and some hybrid methodologies that combine coupled and uncoupled analysis tools, and illustrates their application to a DICAS system for deepwater applications in Campos basin.

DYNAMIC ANALYSIS OF FRAMES WITH MATERIAL AND GEOMETRIC NONLINEARITIES BASED ON THE SEMIRIGID TECHNIQUE

2008 ◽  
Vol 08 (03) ◽  
pp. 415-438 ◽  
Author(s):  
F. T. K. AU ◽  
Z. H. YAN
Keyword(s):  
Dynamic Analysis ◽  
Stiffness Matrix ◽  
Plastic Hinge ◽  
Nonlinear Dynamic Analysis ◽  
Yield Condition ◽  
Computationally Efficient ◽  
Time Step ◽  
Geometric Nonlinearities ◽  
Frame Element ◽  
Sum Of Products

This paper presents a method for nonlinear dynamic analysis of frames with material and geometric nonlinearities which is based on the semirigid technique. The plastic hinge that accounts for the material nonlinearity is modeled as a pseudo-semirigid connection with nonlinear hysteretic moment-curvature characteristics at the element ends. The stiffness matrix of a frame element with material and geometric nonlinearities is expressed as the sum of products of the standard stiffness matrix and the geometric stiffness matrix of the element, with their corresponding correction matrices based on the plasticity factors developed from the section flexural stiffness at the plastic hinge locations. The combined stress yield condition is used for the force state determination of plastic hinges, and force equilibrium iterations and geometry updating for frames are carried out in every time step. When the key parameters of a structure are updated in a time step, the time step is split up into substeps to ensure accuracy while keeping the computations to a reasonable amount. The plastic rotation history can be calculated directly or in an approximate indirect way. The method is computationally efficient and it needs no additional connection elements, which makes it convenient for incorporation into existing linear dynamic analysis programs. Besides, the method can handle accurately and efficiently the dynamic analysis of nonlinear frames using relatively large time steps in conjunction with time step subdivision to cope with key parameter changes. A portal frame is used to verify the correctness of the proposed method. A more complicated five-story frame is used to illustrate the applicability and performance of the proposed method.

Sign in / Sign up

Export Citation Format

Share Document