A Time-Domain Method for Hydroelasticity of a Curved Floating Bridge in Inhomogeneous Waves

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Wei Wei ◽  
Shixiao Fu ◽  
Torgeir Moan ◽  
Chunhui Song ◽  
Shi Deng ◽  
...  
Keyword(s):  
Time Domain ◽  
Time History ◽  
Dynamic Responses ◽  
Irregular Waves ◽  
Inhomogeneous Wave ◽  
Inhomogeneous Waves ◽  
Hydroelastic Analysis ◽  
History Of ◽  
Floating Bridge ◽  
The Time Domain

This paper presents a time-domain hydroelastic analysis method for bridges supported by floating pontoons in inhomogeneous wave conditions. The inhomogeneous wave effect is accounted for by adopting different wave spectra over different regions along the structure, then the time history of inhomogeneous first-order wave excitation forces on the floating pontoons can be obtained. The frequency-domain hydrodynamic coefficients are transformed into the time-domain hydroelastic model using Cummins' equations. The linear hydroelastic responses of a curved floating bridge with end supports, subjected to irregular waves with spatially varying significant wave heights and peak periods, are investigated. Moreover, sensitive analyses are performed to study the effects of the inhomogeneity on the hydroelastic responses. The primary results indicate that the inhomogeneity of the waves has a significant effect on the dynamic responses of the floating bridge.

A Time-Domain Method for Hydroelastic Analysis of Floating Bridges in Inhomogeneous Waves

2017 ◽  
Author(s):  
Shixiao Fu ◽  
Wei Wei ◽  
Shaowu Ou ◽  
Torgeir Moan ◽  
Shi Deng ◽  
...  
Keyword(s):  
Time Domain ◽  
Time Domain Method ◽  
Dynamic Responses ◽  
Irregular Waves ◽  
Frequency Domain Method ◽  
Wave Condition ◽  
Inhomogeneous Waves ◽  
Domain Method ◽  
Hydroelastic Analysis ◽  
Floating Bridge

Based on the three dimensional potential theory and finite element method (FEM), this paper presented a method for time-domain hydroelastic analysis of a floating bridge in inhomogeneous waves. A floating bridge in both regular and irregular waves, is taken as a numerical example. This method is firstly validated by the comparisons of the results between frequency domain method and presented time domain method under regular wave condition. Then the hydroeleastic responses of the floating bridge in waves with spatially varying significant wave height/peak period are presented, with the purpose to illustrate the feasibility of the proposed method. The primary results at this stage indicate that the inhomogeneity of the waves might affect the structure dynamic responses of the floating bridge in waves.

A non-linear model for elastic hysteresis in the time domain: Computational procedure

2020 ◽  
pp. 095440622098202
Author(s):  
MMS Dwaikat ◽  
C Spitas ◽  
V Spitas
Keyword(s):  
Time Domain ◽  
Mechanical Energy ◽  
Numerical Procedure ◽  
Time History ◽  
Computational Procedure ◽  
Continuous Systems ◽  
Full Time ◽  
Proposed Model ◽  
History Of ◽  
The Time Domain

Hysteretic damping of a material or structure loaded within its elastic region is the dissipation of mechanical energy at a rate independent of the frequency of vibration while at the same time directly proportional to the square of the displacement. Generally, reproducing this frequency-independent damping can be computationally complex and requires prior knowledge of the system’s natural frequencies or the full time history of the system’s response. In this paper, a new model and numerical procedure are proposed whereby hysteretic material damping is achieved in the time domain. The proposed procedure is developed based on modifying the viscous model through a correction factor calculated exclusively using the local response. The superiority of the proposed approach lies in its ability to capture material hysteresis without any knowledge of the eigen- or modal frequencies of the system and without knowledge of the past time history of the system’s response or the characteristics of any excitation forces. A numerical procedure is also presented for implementing the proposed model in vibration analysis. The simplicity of the approach enables its generalisation to continuous systems and to systems of multi-degrees of freedom as demonstrated herein. The proposed model is presented as a correction to the viscous damping model which makes it attractive to implement into commercial finite element package using user-defined element subroutines as demonstrated in this study.

Acoustic Impact Technique for Characterization of Defects in Laminated Composites

1993 ◽  
Author(s):  
A. Haque ◽  
Pollapragada K. Raju
Keyword(s):  
Time Domain ◽  
Laminated Composites ◽  
Time History ◽  
Region Of Interest ◽  
Experimental Configuration ◽  
History Of ◽  
Acoustic Impact ◽  
The Time Domain ◽  
Laminated Structures

Abstract The Acoustic Impact Technique (AIT) of nondestructive testing (NDT) has been investigated in detecting gross defects such as delamination in laminated composites. The use of Acoustic Impact Technique has shown encouraging results by previous investigators in identifying defects like delamination and disbonds in honeycomb structures. Very limited work has been reported in the literature about the utility of AIT as a NDT tool for testing in laminated structures. The present work investigates the sensitiveness of the AIT method in detecting delamination in laminated composites in terms of size, shape, position and degree of concentration. The significant advantage of AIT is that this technique is attractive for field applications. The method involves striking the structure with an instrumented impacter in the region of interest and recording the time history of the impulse. The response of the signals received from both good and defective zones of a specimen were analyzed in the time domain. The experimental configuration used by previous investigators was very restrictive. In this study a different approach to AIT is developed. The effectiveness of AIT was evaluated by making a comparative study with ultrasonic C-scan in detecting similar types of defects. The results indicate the sensitiveness of AIT in detecting delamination in laminated composites in terms of size, depth and degree of concentration.

scholarly journals Effect of Modelling Inhomogeneous Wave Conditions on Structural Responses of a Very Long Floating Bridge

2021 ◽  
Vol 9 (5) ◽  
pp. 548
Author(s):  
Jian Dai ◽  
Christos Stefanakos ◽  
Bernt J. Leira ◽  
Hagbart Skage Alsos
Keyword(s):  
Water Environment ◽  
Bridge Structure ◽  
Inhomogeneous Wave ◽  
Wave Condition ◽  
Analysis And Design ◽  
Inhomogeneous Waves ◽  
Modelling Analysis ◽  
Structural Responses ◽  
Floating Bridge ◽  
Wave Conditions

Floating bridges are suitable for connecting land parcels separated by wide and deep waterbodies. However, when the span of the crossing becomes very long, the water environment exhibits inhomogeneities which introduce difficulties to the modelling, analysis and design of the bridge structure. The wave inhomogeneity may be described by means of field measurement and/or numerical simulations. Both approaches face complications when the resolution is much refined. It is thus important to examine the effect of the resolution related to the modelling of inhomogeneous waves on the global structural responses. In this study, a hypothetical crossing at the Sulafjord is chosen, and the wave environment in the year 2015 at 10 positions along the crossing is numerically computed. Next, different inhomogeneous wave conditions are established based on the wave data at 3, 5, and 10 positions, respectively. Time-domain simulations are conducted to examine the effect of different modelling approaches of the inhomogeneous wave condition on the global responses of a long, straight and side-anchored floating bridge.

A novel wave propagation method for measuring viscoelastic properties of pre-strained materials

2021 ◽  
pp. 1-19
Author(s):  
Pierre Lemerle
Keyword(s):  
Wave Propagation ◽  
Viscoelastic Properties ◽  
Time History ◽  
Main Concept ◽  
Frequency Dependent ◽  
Damping Characteristics ◽  
History Of ◽  
Propagation Methods ◽  
The Time Domain ◽  
Waveform Pattern

Abstract Viscoelastic materials are widely used for vibroacoustic solutions due to their ability to mitigate vibration and sound. Wave propagation methods are based on the measurement of the waveform pattern of a transitory pulse in one-dimensional structures. The time evolution of the pattern can be used to deduce the material elasticity and damping characteristics. The most popular propagation methods, namely Hopkinson bar methods, assume no dispersion, i.e. the complex elasticity modulus is not frequency-dependent. This is not significant for resilient materials such as elastomers. More recent approaches have been developed to measure frequency-dependent properties from a pulse propagating in a slender bar. We showed in previous works how to adapt these techniques for shorter samples of materials, representing a real advance, as extrusion is a cumbersome process for many materials. The main concept was to reconstruct the time history of the wave propagating in a composite structure composed of a long incident bar made of a known material and extended by a shorter sample bar. Then the viscoelastic properties of the sample material were determined in the frequency domain within an inverse method held in the time domain. In industry, most isolation solutions using mounts or bushings must support structural weights. This is why it is particularly interesting to know the viscoelastic properties of the material in stressed state. Here, we show how to overcome this challenging issue. The theoretical framework of the computational approach is detailed and the method is experimentally verified.

The Time Domain Simulation of Non-Stationary Road Roughness

2013 ◽  
Vol 423-426 ◽  
pp. 1238-1242
Author(s):  
Hao Wang ◽  
Xiao Mei Shi
Keyword(s):  
Power Spectrum ◽  
Time Domain ◽  
Ride Comfort ◽  
Time History ◽  
Random Excitation ◽  
Power Spectrum Density ◽  
The Road ◽  
Road Roughness ◽  
Spectrum Density ◽  
History Of

The input of road roughness, which affects the ride comfort and the handling stability of vehicle, is the main excitation for the running vehicle. The time history of the road roughness was researched with the random phases, based on the stationary power spectrum density of the road roughness determined by the standards. Through the inverse Fourier transform, the random phases can be used to get the road roughness in time domain, together with the amplitude. Then, the time domain simulation of the non-stationary random excitation when the vehicle ran at the changing speed, would also be studied based on the random phases. It is proved that the random road excitation for the vehicle with the changing speed is stationary modulated evolution random excitation, and its power spectrum density is the stationary modulated evolutionary power spectrum density. And the numerical results for the time history of the non-stationary random inputs were also provided. The time history of the non-stationary random road can be used to evaluate the ride comfort of the vehicle which is running at the changing speed.

System Identification of Jack-Up Platform by Spectral Analysis

2010 ◽  
Author(s):  
X. M. Wang ◽  
C. G. Koh ◽  
T. N. Thanh ◽  
J. Zhang
Keyword(s):  
Spectral Analysis ◽  
System Identification ◽  
Time Domain ◽  
Time History ◽  
Offshore Structures ◽  
Wave Load ◽  
History Of ◽  
Structural Responses ◽  
Jack Up ◽  
Numerical Strategy

For the purpose of structural health monitoring (SHM), it is beneficial to develop a robust and accurate numerical strategy so as to identify key parameters of offshore structures. In this regard, it is difficult to use time-domain methods as the time history of wave load is not available unless output-only methods can be developed. Alternatively, spectral analysis widely used in offshore engineering to predict structural responses due to random wave conditions can be used. Thus the power spectral density (PSD) of structural response may be more appropriate than time history of structural responses in defining the objective (fitness) function for system identification of offshore structures. By minimizing PSD differences between measurements and simulations, the proposed numerical strategy is completely carried out in frequency domain, which can avoid inherent problems rising from random phase angles and unknown initial conditions in time domain. A jack-up platform is studied in the numerical study. A search space reduction method (SSRM) incorporating the use of genetic algorithms (GA) as well as a substructure approach are adopted to improve the accuracy and efficiency of identification. As a result, the stiffness parameters of jack-up legs can be well identified even under fairly noisy conditions.

Dynamic Response of 3D Surface/Embedded Rigid Foundations of Arbitrary Shapes on Multi-Layered Soils in Time Domain

2019 ◽  
Vol 19 (09) ◽  
pp. 1950106 ◽  
Author(s):  
Zejun Han ◽  
Mi Zhou ◽  
Xiaowen Zhou ◽  
Linqing Yang
Keyword(s):  
Dynamic Response ◽  
Frequency Domain ◽  
Time Domain ◽  
Dynamic Stiffness ◽  
Dynamic Responses ◽  
Rigid Foundation ◽  
Layered Soils ◽  
Stiffness Matrices ◽  
The Time Domain ◽  
Arbitrary Shapes

Significant differences between the predicted and measured dynamic response of 3D rigid foundations on multi-layered soils in the time domain were identified due to the existence of uncertainties, which makes the issue a complicated one. In this study, a numerical method was developed to determine the dynamic responses of 3D rigid surfaces and embedded foundations of arbitrary shapes that are bonded to a multi-layered soil in the time domain. First, the dynamic stiffness matrices of the rigid foundations in the frequency domain are calculated via integral domain transformation. Secondly, a dynamic stiffness equation for rigid foundations in the time domain is established via the mixed variables formulation, which is based on the discrete dynamic stiffness matrices in the frequency domain. The proposed method can be applied to the treatment of systems with multiple degrees of freedom without losing the true information that concerns the coupling characteristics. Numerical examples are presented to demonstrate the accuracy of the proposed method for predicting the horizontal, vertical, rocking, and torsional vibrations. Further, a parametric study was carried out to provide insight into the dynamic behavior of the soil–foundation interaction (SFI) while considering soil nonhomogeneity. The results indicate that the elastic modulus of the soil has a significant impact on the dynamic responses of the rigid foundation. Finally, a numerical example of a rigid foundation resting on a six-layered, semi-infinite soil demonstrates that the proposed method can be used to deal with multi-layered media in the time domain in a relatively easy way.

scholarly journals Transient Response of an Impacted Beam and Indirect Impact Force Identification Using Strain Measurements

1994 ◽  
Vol 1 (3) ◽  
pp. 267-278 ◽  
Author(s):  
Hyungsoon Park ◽  
Youn-sik Park
Keyword(s):  
Impulse Response ◽  
Impact Force ◽  
Impulse Response Function ◽  
Time History ◽  
Impulse Response Functions ◽  
Transverse Impact ◽  
History Of ◽  
Convolution Approach ◽  
The Time Domain ◽  
The Impact

The impulse response functions (force-strain relations) for Euler–Bernoulli and Timoshenko beams are considered. The response of a beam to a transverse impact force, including reflection at the boundary, is obtained with the convolution approach using the impulse response function obtained by a Laplace transform and a numerical scheme. Using this relation, the impact force history is determined in the time domain and results are compared with those of Hertz's contact law. In the case of an arbitrary impact, the location of the impact force and the time history of the impact force can be found. In order to verify the proposed algorithm, measurements were taken using an impact hammer and a drop test of a steel ball. These results are compared with simulated ones.

Assessment of Allowable Sea States During Installation of Offshore Wind Turbine Monopiles With Shallow Penetration in the Seabed

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Lin Li ◽  
Wilson Guachamin Acero ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Time Domain ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Offshore Wind Turbines ◽  
Heavy Lift ◽  
Characteristic Values ◽  
Limiting Parameters ◽  
The Time Domain ◽  
Penetration Depths

Installation of offshore wind turbines (OWTs) requires careful planning to reduce costs and minimize associated risks. The purpose of this paper is to present a method for assessing the allowable sea states for the initial hammering process (shallow penetrations in the seabed) of a monopile (MP) using a heavy lift floating vessel (HLV) for use in the planning of the operation. This method combines the commonly used installation procedure and the time-domain simulations of the sequential installation activities. The purpose of the time-domain simulation is to quantitatively study the system dynamic responses to identify critical events that may jeopardize the installation and the corresponding limiting response parameters. Based on the allowable limits and the characteristic values of the limiting response parameters, a methodology to find the allowable sea states is proposed. Case studies are presented to show the application of the methodology. The numerical model of the dynamic HLV–MP system includes the coupling between HLV and MP via a gripper device, and soil–MP interaction at different MP penetration depths. It is found that the limiting parameters are the gripper force and the inclination of the MP. The systematic approach proposed herein is general and applies to other marine operations.

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