Estimation of Equivalent Dynamic Amplification Factor (EDAF) on a Jacket Structure

2013 ◽  
Author(s):  
Gro Sagli Baarholm ◽  
Atle Johansen ◽  
Jørn Birknes ◽  
Sverre Haver
Keyword(s):  
Dynamic Response ◽  
Linear Time ◽  
Limit State ◽  
Wave Model ◽  
Ultimate Limit State ◽  
Static Response ◽  
Dynamic Amplification Factor ◽  
Irregular Wave ◽  
The North ◽  
Dynamic Amplification

Non-linear time domain irregular wave simulations have been performed for the Kvitebjørn jacket platform located in the North Sea with the aim to quantify the dynamic amplification. The jacket is a slender structure installed in about 190m water depth. For each of the selected extreme sea states both quasi-static and dynamic response simulations have been carried out for several wave realizations using different seeds. Based on the quasi-static response and dynamic response, equivalent dynamic amplification factors (EDAFs) were calculated for different response measures in the jacket. EDAF is the factor one has to multiply the q-probability quasi-static response with in order to obtain an adequate estimate of the q-probability dynamic response. The EDAFs are to be used in ultimate limit state (ULS) and accidental limit state (ALS) analyses of the platform. Simulations were performed applying a Gaussian wave with Wheeler stretching and a second-order wave model. This paper focuses on the selection of wave kinematics method and on the establishment of the EDAF analysis procedure.

Joint Description Methods of Wind and Waves for the Design of Offshore Wind Turbines

2009 ◽  
Vol 43 (3) ◽  
pp. 23-33 ◽  
Author(s):  
Kim E. Mittendorf
Keyword(s):  
Wind Energy ◽  
Wind Wave ◽  
Limit State ◽  
Wave Model ◽  
Design Guidelines ◽  
Offshore Wind ◽  
Ultimate Limit State ◽  
Wave Loads ◽  
Offshore Wind Energy ◽  
The North

AbstractWind and wave loads are equally important for the design of offshore wind energy structures. For the design against an ultimate limit state or fatigue, the engineer has to estimate the combination of loads that are likely to occur simultaneously during the design life of the wind turbine. This is quite a complex task, involving different wind/wave models, load-calculation methods and statistical analysis of simultaneous extreme wind and wave conditions. Moreover, reliable and realistic methods for the assessment of the service life of an offshore wind energy converter under combined wind and wave loads are necessary. However, the current design guidelines (Det Norske Veritas or German Lloyd) provide hardly any information on how to model the wind and wave correlation. In this article, several approaches for obtaining the required wind-wave correlation for the design have been investigated. Manual wave forecasting methods, spectral sea state descriptions and numerical wave model data have been compared to simultaneously measured wind and wave data from the FINO research platform in the German Bight of the North Sea. The used approaches are general and can be easily applied to different data sets from different regions.

Implementation of a Method for Free-Spanning Pipeline Analysis

2021 ◽  
Author(s):  
Joannes Gullaksen
Keyword(s):  
Dynamic Response ◽  
Flow Direction ◽  
Limit State ◽  
Cross Flow ◽  
Ultimate Limit State ◽  
Force Model ◽  
Short Term ◽  
Direct Wave ◽  
Current Loading

Abstract The scope of this paper is to provide a method implemented in an application for assessment of dynamic response of free spanning pipelines subjected to combined wave and current loading. The premises for the paper are based on application development within pipeline free span evaluation in a software development project. A brief introduction is provided to the basic hydrodynamic phenomena, principles and parameters for dynamic response of pipeline free spans. The choice of method for static and dynamic span modelling has an influence on calculated modal frequencies and associated stresses. Due to the importance of frequencies and stresses for fatigue and environmental loading calculations, the choice of analysis approach influences the partial safety factor format. The aim of the structural analysis is to provide the necessary input to the calculations of VIV and force model response, and to provide realistic estimations of static loading from functional loads. Environmental flow conditions are implemented in the application, such as steady flow due to current, oscillatory flow due to waves and combined flow due to current and waves. Combined wave and current loading include the long-term current velocity distribution, short-term and long-term description of wave-induced flow velocity amplitude and period of oscillating flow at the pipe level and return period values. Inline and cross-flow vibrations are considered in separate response models. For pipelines and risers, modes are categorized in in-line or cross-flow direction. A force model is also considered for the short-term fatigue damage due to combined current and direct wave actions. Design criteria can be specified for ultimate limit state (ULS) and fatigue limit state (FLS) due to in-line and cross-flow vortex induced vibrations (VIV) and direct wave loading.

Dynamic response of bridges under travelling loads

1993 ◽  
Vol 20 (2) ◽  
pp. 287-298 ◽  
Author(s):  
J. L. Humar ◽  
A. M. Kashif
Keyword(s):  
Dynamic Response ◽  
Rational Design ◽  
Weight Ratio ◽  
Experimental Investigations ◽  
Speed Ratio ◽  
Force Model ◽  
Beam Model ◽  
Dynamic Amplification Factor ◽  
Design Procedures ◽  
Dynamic Amplification

In spite of a number of analytical and experimental investigations on the dynamic response of bridges to moving vehicle loads, the controlling parameters that govern the response have not been clearly identified. This has, in turn, inhibited the development of rational design procedures. Based on an analytical investigation of the response of a simplified beam model traversed by a moving mass, the present study identifies the governing parameters. The results clearly show why attempts to correlate the response to a single parameter, either the span length or the fundamental frequency, are unsuccessful. Simple design procedures are developed based on relationships between the speed ratio, the weight ratio, and the dynamic amplification factors; and a set of design curves are provided. Key words: dynamic response of bridges, vehicle–bridge interaction, moving force model, moving sprung mass model, dynamic amplification factor.

Recent Advances in Pipeline Free Span Design: A New Revision of DNV-RP-F105

2016 ◽  
Author(s):  
Knut Vedeld ◽  
Håvar Sollund ◽  
Olav Fyrileiv
Keyword(s):  
Dynamic Response ◽  
Limit State ◽  
Cross Flow ◽  
Ease Of Use ◽  
Direct Result ◽  
Ultimate Limit State ◽  
Vortex Induced Vibrations ◽  
Load Effects ◽  
Pipeline Design ◽  
Wave Induced

Pipeline free span design has evolved from basic avoidance criteria in the DNV ’76 rules [1], to fatigue and ultimate limit state considerations in Guideline no. 14 [2]. Modern multimode, multi-span free span design is predominantly performed according to DNV-RP-F105 [3]. In 2006, the latest revision of DNV-RP-F105 [3] was written as a direct result of extensive research, performed due to significant free span challenges in the Ormen Lange pipeline project. DNV-RP-F105 was at the time, and still is, the only pipeline design code giving contemporary design guidance for vortex induced vibrations (VIV) and direct wave loading design for pipelines in free spans. The last revision of DNV-RP-F105 included a few, but highly important advances, particularly the consideration for multi-mode and multi-span pipeline dynamic response behavior. In the 10 years that have followed, no breakthroughs of similar magnitude have been achieved for pipeline free spans, but a large number of incremental improvements to existing calculation methods, and some novel advances in less critical aspects of VIV understanding have been made. As a result, DNV-RP-F105 has recently been revised to account for these advances, which include improved frequency-domain analyses of wave-induced fatigue, a new response model for cross-flow VIV in low Keulegan-Carpenter (KC) regimes in pure waves, new analytical methods for dynamic response calculations of short spans in harsh conditions, and extensive guidance on how to apply the recommended practice for assessment of fatigue and extreme environmental load effects on curved structural members such as spools, jumpers and manifold flexloops. This paper gives an overview of most of the important changes and updates to the new revision of DNV-RP-F105. Case studies are used to demonstrate the importance and effects of the changes made, and to some extent how the revision of DNV-RP-F105 can enhance its applicability and ease of use.

scholarly journals Damped dynamic response of strengthened beams by composite coats under moving force by FEM

2018 ◽  
Vol 106 (2) ◽  
pp. 206
Author(s):  
Abdennacer Chemami ◽  
Youcef Khadri ◽  
Sabiha Tekili ◽  
El Mostafa Daya ◽  
Ali Daouadji ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Numerical Study ◽  
Moving Load ◽  
Damping Ratio ◽  
Time Integration ◽  
Superposition Method ◽  
Dynamic Amplification Factor ◽  
Aluminum Composite ◽  
Strengthened Beam ◽  
Dynamic Amplification

This paper presents a numerical study of the free and damped forced vibration of simply-supported beams with composite coats subjected to a moving load by use of finite elements method. Three types of beam configurations, aluminum, composite and strengthened beam are investigated. The equation of motion of the beam is solved using the modal superposition method and integrated by applying the Newmark time integration procedure. Good agreements were achieved between the FEM and analytical solutions. The damped dynamic response, critical velocities and the dynamic amplification factor of the beam are calculated for different parameters such as the thickness ratio, the fiber orientation of the coat and damping ratio.

Dynamic Response of High Steep Rock Slopes Based on Wenchuan Near-Field Seismic Motion Characteristics

2010 ◽  
Vol 168-170 ◽  
pp. 1090-1097
Author(s):  
Shi Guo Xiao ◽  
Wen Kai Feng
Keyword(s):  
Numerical Analysis ◽  
Dynamic Response ◽  
Amplification Factor ◽  
Near Field ◽  
Seismic Load ◽  
Rock Slopes ◽  
Dynamic Amplification Factor ◽  
Seismic Motion ◽  
Dynamic Amplification ◽  
Motion Characteristics

Near-field seismic motion characteristics are analyzed in accordance with records of the 2008 Ms8.0 Wenchuan Earthquake measured at Wolong Station, upon which the determination of seismic load is introduced. Dynamic response features, such as acceleration, displacement and stress, of high steep rock slopes on the banks of Zipingpu Reservoir at a variety of locations resulting from horizontal seismic force are analyzed with a numerical analysis routine. The dynamic amplification factor on the slope top is determined, leading to a characterization of the mode of failure of the high steep slope. Analyses show that the dynamic amplification factor at the top of the slopes is about 1.34; however, dynamic response deformation features and stress state at different positions on the slope vary. Earthquake damage of the high steep rock slopes consists mainly of partial avalanche of the rock mass at the top of the slopes by joint cutting. Field investigations after the earthquake have partially confirmed the numerical analysis results presented in this paper.

Dynamic Behaviour of Minimum Platforms Under Random Seas

2003 ◽  
Author(s):  
Micaela Pilotto ◽  
Beverley F. Ronalds
Keyword(s):  
Dynamic Response ◽  
Dynamic Behaviour ◽  
Amplification Factor ◽  
Finite Element Models ◽  
Dynamic Amplification Factor ◽  
Maximum Value ◽  
Random Seas ◽  
Exponential Stretching ◽  
Structural Configurations ◽  
Dynamic Amplification

This paper describes the dynamic response of minimum facilities with different structural configurations which are subjected to random seas. The finite element models are kept simple with the aim of focusing on the physics of the phenomena involved. The response is studied in terms of the dynamic amplification factor (DAF), representing the ratio between the dynamic and the static response. Two different formulations of the DAF under random seas are compared. The first is defined in terms of standard deviation (DAF1), the second in terms of the most probable maximum value (DAF2). Ringing is observed to be a relevant feature of the dynamic response and to affect primarily the braced monopod configurations. Ringing is detected using DAF2. The paper also addresses the importance of the kinematic representation above the still water level. Different methods of stretching the velocity field in the wave zone (delta, Wheeler and exponential stretching) are shown to have a significant impact on the dynamic response of the platforms.

Ultimate Limit State Assessment of the M.V. Derbyshire Hull Structure

2006 ◽  
Author(s):  
Jeom Kee Paik ◽  
Jung Kwan Seo ◽  
Jae Myung Lee ◽  
Jae Hyung Park
Keyword(s):  
Limit State ◽  
Ultimate Limit State ◽  
Stiffened Panels ◽  
Hull Girder ◽  
North West ◽  
Water Ingress ◽  
The North ◽  
Formal Safety Assessment ◽  
Hull Structure ◽  
Ultimate Limit

The Capesize bulk carrier, M.V. Derbyshire, sank in the North West Pacific during typhoon Orchid in September 1980 when she was on a voyage from Canada to Japan carrying fine iron ore concentrates. Since then, extensive investigations of the vessel sinking have previously been made in the literature primarily by the formal safety assessment (FSA) technique to explore the loss causes, but serious speculation on the failure of hull structures has been lacking in such investigations. The present paper investigates the possibility of the vessel sinking initiated by the failure of hull structures rather than by other loss scenarios such as hatch cover failure subsequent to water ingress into the cargo holds. Ultimate limit state assessments of individual stiffened panels and hulls of the M.V. Derbyshire under extreme bending moments during the last voyage in storm are made using ALPS/ULSAP and ALPS/HULL computer programs. It is concluded that the M.V. Derbyshire could have sunk by hull girder collapse with or even without unintended water ingress into cargo holds. Important insights and findings developed from the present study are summarized.

scholarly journals Dynamic Response of an End-Supported Pontoon Bridge due to Wave Excitation: Numerical Predictions versus Measurements

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Knut Andreas Kvåle ◽  
Ole Øiseth
Keyword(s):  
Dynamic Response ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Limit State ◽  
Ultimate Limit State ◽  
Linear Potential ◽  
Beam Model ◽  
Numerical Predictions ◽  
Power Spectral ◽  
Standard Deviations

Herein, numerical predictions of the dynamic response of an existing floating pontoon bridge are compared with the measured dynamic response. Hydrodynamic coefficients that describe the fluid-structure interaction and the wave transfer functions are obtained by applying linear potential theory. The results obtained from the hydrodynamic analysis are combined with a beam model of the bridge in a finite element method (FEM) framework to enable stochastic response prediction through the power spectral density method. The standard deviations of the predicted accelerations are compared with the standard deviations of the measured accelerations, and the overall quality of the prediction model is discussed. Predictions with sea states related to the serviceability limit state (SLS) and ultimate limit state (ULS) conditions used in design of the bridge are emphasized. To investigate the behaviour more in depth, a measurement segment is chosen and predictions of the displacement response power spectral density due to excitation characterized by the recorded sea surface elevation are compared with those obtained from the corresponding response measurements. A decent agreement is obtained for both cases when using the model as it is and with waves as the only excitation source, but significant discrepancies are present, in particular, for the torsional components. By including preliminary contributions from wind action and relying on a model optimized against measured modal parameters, a satisfactory agreement is obtained. The effect on the response of an uncertain structural damping is also quantified and concluded to be significant within realistic damping levels.

Ultimate Limit State Assessment of the M.V. Derbyshire Hull Structure

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Jeom Kee Paik ◽  
Jung Kwan Seo ◽  
Bong Ju Kim
Keyword(s):  
Limit State ◽  
Ultimate Limit State ◽  
Stiffened Panels ◽  
Hull Girder ◽  
North West ◽  
Water Ingress ◽  
The North ◽  
Formal Safety Assessment ◽  
Hull Structure ◽  
Ultimate Limit

The Capesize bulk carrier, M.V. Derbyshire, sank in the North West Pacific during typhoon Orchid in September 1980 when she was on a voyage from Canada to Japan carrying fine iron ore concentrates. Since then, extensive investigations of the vessel sinking have previously been made in the literature primarily by the formal safety assessment technique to explore the loss causes, but serious speculation on the failure of hull structures has been lacking in such investigations. The present paper investigates the possibility of the vessel sinking initiated by the failure of hull structures rather than by other loss scenarios, such as hatch cover failure subsequent to water ingress into the cargo holds. Ultimate limit state assessments of individual stiffened panels and hulls of the M.V. Derbyshire under extreme bending moments during the last voyage in storm are made using ALPS/ULSAP and ALPS/HULL computer programs. It is concluded that the M.V. Derbyshire could have sunk by hull girder collapse with or even without unintended water ingress into cargo holds. Important insights and findings developed from the present study are summarized.

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