Structural Response to Non-Stationary Thunderstorm Outflows

2020 ◽  
Author(s):  
Dae Kun Kwon ◽  
Giovanni Solari ◽  
Ahsan Kareem
Keyword(s):  
Boundary Layer ◽  
Time Domain ◽  
Paradigm Shift ◽  
Stationary Process ◽  
Response Spectrum ◽  
Structural Response ◽  
Kinematics And Dynamics ◽  
Statistical Features ◽  
Simulation Based ◽  
The Time Domain

The mechanics associated with thunderstorm outflows differ significantly from traditional turbulence in boundary layer winds both in its kinematics and dynamics. The key distinguishing attributes are the contrasting velocity profile with height, a rapid increase in speed, and the statistical features of the energetic gusts in the wind field, exhibiting a strong non-stationarity. This raises serious questions regarding the applicability of conventional stationary process-based theories, thus calling for a paradigm shift. This chapter reviews popular approaches concerning the structural analysis of non-stationary thunderstorm outflows, such as evolutionary power spectrum-based analysis, wavelet-based analysis, thunderstorm response spectrum technique involving the equivalent wind spectrum, and hybrid simulation-based analysis in the time domain. Finally, some preliminary comparisons between the results obtained using these different methods are presented.

Coupled Time-Domain Hydro-Elastic Simulation for Submerged Floating Tunnel Under Wave Excitations

2021 ◽  
Author(s):  
Chungkuk Jin ◽  
Sung-Jae Kim ◽  
MooHyun Kim
Keyword(s):  
Time Domain ◽  
Domain Model ◽  
Mooring Line ◽  
Wave Forces ◽  
Rod Theory ◽  
Discrete Module ◽  
Simulation Based ◽  
Submerged Floating Tunnel ◽  
The Time Domain ◽  
Elastic Simulation

Abstract We develop a fully-coupled time-domain hydro-elasticity model for the Submerged Floating Tunnel (SFT) based on the Discrete-Module-Beam (DMB) method. Frequency-domain simulation based on 3D potential theory results in multibody’s hydrodynamic coefficients and excitation forces for tunnel sections. Subsequently, we build the time-domain model with the multibody Cummins equation and external stiffness matrix from the Euler-Bernoulli and Saint-Venant torsion theories. We establish the mooring line model with rod theory and couple components with translational springs at their respective connection locations. We then compare the dynamic motions, wave forces, and mooring tensions between the present and Morison-equation-based elastic models under regular wave excitations at different submergence depths. The present model is especially important for the shallowly submerged tunnel in which the Morison model shows exaggerated motions, especially at high-frequency range.

Fault Diagnosis of Motor Rotor Based on Fuzzy C-Means Clustering Analysis

2013 ◽  
Vol 273 ◽  
pp. 409-413 ◽  
Author(s):  
Yu Xiang Cao ◽  
Xue Jun Li ◽  
Ling Li Jiang
Keyword(s):  
Time Domain ◽  
Clustering Analysis ◽  
Statistical Features ◽  
Fuzzy C Means ◽  
Time Domain Signal ◽  
Fuzzy C Means Clustering ◽  
Important Means ◽  
Fault Diagnostic ◽  
Characteristic Features ◽  
The Time Domain

For the fuzziness of the fault symptoms in motor rotor, this paper proposes a fault diagnostic method which based on the time-domain statistical features and the fuzzy c-means clustering analysis (FCM). This method is to extract the characteristic features of time-domain signal via time-domain statistics and to import the extracted characteristic vector to classifier. And then the fuzzy c-means realizes the classification by confirming the distance among samples, which is based on the degree of membership between the sample and the clustering center. The fault diagnostic cases of motor rotor show that the method which bases on the time-domain statistical features-FCM can detect the rotor fault effectively and distinguish the different types of fault correctly. Therefore, it can be used as an important means of rotor fault identification.

Advances in Offshore Structural Analysis Using Response-Based Time-Domain Approach

2021 ◽  
Author(s):  
Johyun Kyoung ◽  
Sagar Samaria ◽  
Jeffrey O’Donnell ◽  
Sudhakar Tallavajhula
Keyword(s):  
Structural Analysis ◽  
Fracture Mechanics ◽  
Time Domain ◽  
Structural Strength ◽  
Structural Response ◽  
Life Extension ◽  
Environmental Loads ◽  
Analysis Methodology ◽  
Non Linear ◽  
The Time Domain

Abstract Demand for life extension assessments of floating offshore platforms continues to grow worldwide. Conventional structural analysis methods have limited ability to accurately capture non-linear environmental loading, non-linear loading by the mooring and riser systems, and resulting higher order hull responses. The uncertainties are typically managed by the factors of safety applied in the structural analysis. Time domain structural analyses have long promised to improve analysis accuracy and reduce these uncertainties. This paper describes a comprehensive and practical time domain structural analysis methodology applied to a deep-water semi-submersible-type floating platform including results for structural strength and fatigue. In addition, the time domain structural analysis was extended for use in fracture mechanics and the assessment of notional weld flaws to facilitate specification of impactful non-destructive examination (NDE). Present time domain structural analysis methodology employs a response-based finite element analysis (FEA) conducted in the time domain. All external environmental loads and inertial forces are converted to a response-based stress-time history. Previously, conventional time domain structural analysis involves massive computation resources to resolve solutions at every time interval. Present methodology significantly improves computational efficiency to be practical in real-world problems. The improvement is achieved by decomposing the structural response into a set of multiple load components selected on the bases of function for hull motion response and environmental loadings. Structural response in time domain is directly obtained by synthesizing the load components. An actual time domain structural response is captured effectively and efficiently to simulate the strength and fatigue criterion for the structure with consistent environmental loads and hull responses. Utilizing the level of detail provided by the time domain structural analysis methodology, a fracture mechanics evaluation of notional initial flaws (engineering criticality assessments – ECAs) can be conducted providing meaningful technical basis for in-service NDE and life extension assessments. The procedures for fatigue crack growth and fracture documented in BS 7910 were employed to derive the smallest initial flaws (critical initial flaws) that may result in structural failure during a facility's lifetime. A comparison indicates that conventional structural analysis methods provide conservative results for both structural strength and fatigue damage calculations resulting from the linear assumption of environmental loads and hull responses. Present time domain structural analysis methodology provides an innovative, cutting-edge approach providing accuracy and fewer uncertainties, which can be pragmatically used during a typical project.

Approximate Structural Response Characterization Using Parametric and Envelope Models for Multimodal Systems

1986 ◽  
Vol 108 (1) ◽  
pp. 39-43
Author(s):  
P. Davies ◽  
J. K. Hammond
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Structural Response ◽  
Parametric Models ◽  
Response Signal ◽  
Response Characteristics ◽  
Multimodal Systems ◽  
Time Domain Response ◽  
The Time Domain

In the study of the response of systems to an excitation there are circumstances when it is desirable to obtain some overall or average characterization of the system and its response rather than a detailed description. In this paper two methods are used to describe the overall features of the system: one appropriate for the frequency domain and one for the time domain. For modally dense systems the main features of the frequency response function are described in terms of low-order parametric models. While these models may be adequate for the frequency domain representation, they may not produce a good approximation to the response of the system in the time domain. The second approach relates the envelope of the input signal to the envelope of the response signal, in order to describe the overall time domain response characteristics.

scholarly journals A New Elastoplastic Time-History Analysis Method for Frame Structures

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Qianqian Liang ◽  
Chen Zhao ◽  
Jun Hu
Keyword(s):  
Periodic Point ◽  
Time Domain ◽  
Response Spectrum ◽  
Time History ◽  
Specific Yield ◽  
Seismic Load ◽  
Structural Systems ◽  
History Analysis ◽  
The Time Domain ◽  
Fracture Stiffness

This study aimed to analyze the formation and application of the time-domain elastoplastic response spectrum. The elastoplastic response spectrum in the time domain was computed according to the trilinear force-restoring model. The time-domain elastoplastic response spectrum corresponded to a specific yield strength coefficient, fracture stiffness, and yield stiffness. However, the force-restoring models corresponding to different structural systems and the states of the structural systems at different moments were not the same. Therefore, the dynamic characteristics of a particular periodic point corresponding to a particular structure were meaningful for the elastoplastic response spectrum. In addition, the curve in the time-domain dimension along the periodic point truly reflected the real-time response of the structure when the structure encountered a seismic load.

Modeling and Simulation Based on Ultra-Wideband Pulse Source of Time-Domain Reflectometer

2012 ◽  
Vol 220-223 ◽  
pp. 1418-1422
Author(s):  
Li Xia Mou ◽  
Ling He ◽  
Yong Cao
Keyword(s):  
Modeling And Simulation ◽  
Time Domain ◽  
Ultra Wideband ◽  
Major Premise ◽  
Pulse Source ◽  
Key Factors ◽  
Simulation Based ◽  
The Time Domain ◽  
Time Domain Reflectometer

The ultra-wideband pulse source is one of the key factors which decide the time-domain reflectometer’s specification including the testing bandwidth’s accuracy and veracity. Design a good pulse source is the major premise to improve the time-domain reflectometer’s performance. This paper introduced a new style of simulation realization using ADS2009. This simulation focused on the analyses of the importance of the pulse source in the time-domain reflectometer, described pulse source’s pivotal component step recover the diode’s characteristic and accomplished the modeling analyses.

Apodisation in the time domain

1992 ◽  
Vol 2 (4) ◽  
pp. 615-620
Author(s):  
G. W. Series
Keyword(s):  
Time Domain ◽  
The Time Domain
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