Structural response reconstruction with transmissibility concept in frequency domain

2011 ◽  
Vol 25 (3) ◽  
pp. 952-968 ◽  
Author(s):  
S.S. Law ◽  
J. Li ◽  
Y. Ding
Keyword(s):  
Frequency Domain ◽  
Structural Response ◽  
Response Reconstruction

Damage Detection of a Substructure Based on Response Reconstruction in Frequency Domain

2013 ◽  
Vol 569-570 ◽  
pp. 823-830 ◽  
Author(s):  
Jun Li ◽  
Siu Seong Law ◽  
Yong Ding
Keyword(s):  
Frequency Domain ◽  
Damage Identification ◽  
Structural Response ◽  
Element Model ◽  
Frame Structure ◽  
Identification Algorithm ◽  
Response Reconstruction ◽  
The Difference ◽  
And Performance ◽  
Response Vector

A substructural damage identification approach based on structural response reconstruction in frequency domain is presented. The response reconstruction is based on transforming the measured responses into responses at other locations with the transmissibility matrix and then the relationship between two sets of response vectors is formulated. The damage identification is conducted by minimizing the difference between a measured response vector and the reconstructed response vector. Measured acceleration responses from the damaged substructure and the finite element model of the intact substructure only are required in the identification algorithm. A dynamic response sensitivity-based method with the adaptive Tikhonov regularization technique is adopted for the damage identification with improved results from noisy measurements. A seven-storey frame structure is taken as an example to illustrate the effectiveness and performance of the proposed approach.

A Novel Solution to Compute Stress Time Series in Nonlinear Hydro-Structure Simulations

2015 ◽  
Author(s):  
Fabien Bigot ◽  
François-Xavier Sireta ◽  
Eric Baudin ◽  
Quentin Derbanne ◽  
Etienne Tiphine ◽  
...  
Keyword(s):  
Time Series ◽  
Frequency Domain ◽  
Time Domain ◽  
Hot Spot ◽  
Structural Response ◽  
Container Ship ◽  
Time Step ◽  
Computation Cost ◽  
Hull Girder ◽  
Non Linear

Ship transport is growing up rapidly, leading to ships size increase, and particularly for container ships. The last generation of Container Ship is now called Ultra Large Container Ship (ULCS). Due to their increasing sizes they are more flexible and more prone to wave induced vibrations of their hull girder: springing and whipping. The subsequent increase of the structure fatigue damage needs to be evaluated at the design stage, thus pushing the development of hydro-elastic simulation models. Spectral fatigue analysis including the first order springing can be done at a reasonable computational cost since the coupling between the sea-keeping and the Finite Element Method (FEM) structural analysis is performed in frequency domain. On the opposite, the simulation of non-linear phenomena (Non linear springing, whipping) has to be done in time domain, which dramatically increases the computation cost. In the context of ULCS, because of hull girder torsion and structural discontinuities, the hot spot stress time series that are required for fatigue analysis cannot be simply obtained from the hull girder loads in way of the detail. On the other hand, the computation cost to perform a FEM analysis at each time step is too high, so alternative solutions are necessary. In this paper a new solution is proposed, that is derived from a method for the efficient conversion of full scale strain measurements into internal loads. In this context, the process is reversed so that the stresses in the structural details are derived from the internal loads computed by the sea-keeping program. First, a base of distortion modes is built using a structural model of the ship. An original method to build this base using the structural response to wave loading is proposed. Then a conversion matrix is used to project the computed internal loads values on the distortion modes base, and the hot spot stresses are obtained by recombination of their modal values. The Moore-Penrose pseudo-inverse is used to minimize the error. In a first step, the conversion procedure is established and validated using the frequency domain hydro-structure model of a ULCS. Then the method is applied to a non-linear time domain simulation for which the structural response has actually been computed at each time step in order to have a reference stress signal, in order to prove its efficiency.

Spectrum-Compatible Earthquake Records and Their Influence on the Seismic Response of Reinforced Concrete Structures

2016 ◽  
Vol 32 (1) ◽  
pp. 101-123 ◽  
Author(s):  
Ramon L. Gascot ◽  
Luis A. Montejo
Keyword(s):  
Frequency Domain ◽  
Structural Response ◽  
Strong Motion ◽  
Continuous Wavelet ◽  
Earthquake Records ◽  
Inelastic Demand ◽  
Target Spectrum ◽  
Motion Characteristics ◽  
Frequency Domain Approach ◽  
Original Characteristic

Three different methodologies for the generation of spectrum-compatible records are evaluated: wavelet-based modification of seed records, seed record adjustment based on the continuous wavelet transform, and synthetic record generation in the frequency domain. It was found that the three methodologies are capable of generating compatible records with an acceptable level of match. However, the records generated using the frequency domain approach exhibit unrealistic strong motion characteristics and a tendency to induce less inelastic demand in the structures. In the case of methodologies based on modification of actual earthquake records, it was found that when the seed records are selected based on their initial compatibility with the target spectrum, the resultant compatible records not only better retain the original characteristic of the records but the variability in the structural response is reduced.

scholarly journals Assessment of Structural Performance and Integrity for Vibration-based Energy Harvester in Frequency Domain

Electronics ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 357
Author(s):  
Ji-Won Jin ◽  
Ki-Weon Kang
Keyword(s):  
Frequency Domain ◽  
Natural Frequency ◽  
Production Efficiency ◽  
Performance Test ◽  
Energy Harvester ◽  
Structural Integrity ◽  
Structural Response ◽  
Structural Performance ◽  
Railway Vehicle ◽  
Response Analysis

A vibration-based energy harvester (VEH) utilizes vibrations originated from various structures and specifically maximizes the displacement of its moving parts, using the resonance between the frequency of external vibration loads from the structure and the natural frequency of VEH to improve power production efficiency. This study presents the procedure to evaluate the structural performance and structural integrity of VEH utilized in a railway vehicle under frequency domain. First of all, a structural performance test was performed to identify the natural frequency and assess the structural response in frequency domain. Then, the static structural analysis was carried out using FE analysis to investigate the failure critical locations (FCLs) and effect of resonance. Finally, we conducted a frequency response analysis to identify the structural response and investigate the structural integrity in frequency domain. Based on these results, the authors assessed the structural performance and integrity of VEHs in two versions.

scholarly journals Structural Response In The Frequency Domain

2020 ◽  
Author(s):  
Kevin Murphy ◽  
Ismail Orabi
Keyword(s):  
Frequency Domain ◽  
Structural Response

Evaluation of Surface Vibrations in the Low and High Frequency Domain

1995 ◽  
Author(s):  
Peter Fischer ◽  
Helmut J. Pradlwarter ◽  
Gerhart I. Schuëller
Keyword(s):  
Frequency Domain ◽  
High Frequency ◽  
Flow Characteristics ◽  
Low Frequency ◽  
Structural Response ◽  
Short Wave ◽  
Fe Model ◽  
Special Cases ◽  
Wide Range ◽  
Surface Vibrations

Abstract The frequency domain of many problems in structural dynamics encompasses a wide range, covering nearly static behavior up to vibration flow characteristics similar to heat transfer. This work presents an uniform approach for low and high frequency vibration analysis, which is based on Finite Element modeling of the structure. Vibrations in the low frequency range are determined by an efficient superposition technique of complex modes, which accounts accurately for any linear damping effect. The modal method is extended to the high frequency domain by applying different levels of averaging to the response and eigenfrequencies and by the introduction of random properties of modeshapes. The high frequency domain is defined by the size of the Finite Elements, i.e. short wave lengths of high frequency modeshapes cannot be represented by the FE-model. The response computation of isolated structures is extended to substructures of complex systems by prescribing stochastic multi-support base excitation at the substructure boundaries. It may be noted, that the presented approach of stochastic high frequency dynamics contains, as special cases, the expressions of the structural response of Statistical Energy Analysis, Bolotin’s integral method and the results of Asymptotic Modal Analysis.

Simulation of Fluid Sloshing for Decreasing the Response of Structural Systems

2014 ◽  
Author(s):  
İlker Vuruşkan ◽  
Cüneyt Sert ◽  
Mehmet Bülent Özer
Keyword(s):  
Frequency Domain ◽  
Structural Model ◽  
Harmonic Component ◽  
Structural Response ◽  
Coupled System ◽  
Frequency Domain Analysis ◽  
Surface Shape ◽  
Structural Systems ◽  
Total Force ◽  
Ansys Fluent

In the last decade, there is a renewed interest in the integration of a sloshing tank into structural systems to decrease the vibrations of the structure. The purpose of this study is to try different numerical simulation programs for further use in studies in evaluation of the effectiveness of the sloshing tank absorbers for structural systems. The programs chosen for sloshing simulations are COMSOL Multiphysics®, ANSYS CFX and ANSYS-FLUENT. In the numerical simulations, the free surface shape during sloshing will be simulated under small and large amplitude sinusoidal displacements. The results obtained using different software will be compared with the results of the experiments reported in literature. Since the purpose is to use the sloshing forces on the container to decrease the structural response, the total force on the container walls is calculated and compared with the reported experimental results. The dynamics of a container coupled with the a structural model is simulated and forces applied on the container walls are analyzed in the frequency domain which is important in understanding the tuning of the vibration absorber. To the best of authors’ knowledge, in a fluid-structure coupled system the frequency domain analysis of the container wall forces at varying amplitudes of sinusoidal excitation is not presented in literature. The results showed even though higher harmonic forcing magnitudes increase with increasing base motion, the fundamental harmonic component does not change significantly.

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.

Investigation and Modification of Frequency Response Function Using Digital Fourier Analysis for High Speed Dynamic Testing Facility

2009 ◽  
Author(s):  
Chandrashekhar K. Thorbole ◽  
Keshavanarayana S. Raju
Keyword(s):  
Frequency Response ◽  
Frequency Domain ◽  
Response Function ◽  
Time Domain ◽  
Frequency Response Function ◽  
Detection System ◽  
Structural Response ◽  
Wave Form ◽  
Data Set ◽  
Load Detection

The increasing application of composites in the aviation and automobile industry demands a better understanding of composite material behavior under high loading rate. This shall provide a better insight of actual loads on occupants while preserving livable crashworthy structure. In this study, a high stroke rate MTS servo-hydraulic testing machine is used to characterize the behavior of composite materials at high strain rates. At higher stroke rates, the output of the load detection system acquired by the load cell deviates from the true load-time wave form of the specimen. This is due to the convolution of the structural response of the detection system with the true characteristic of the specimen. To identify the true nature of the specimen load-time behavior, the de-convolution of the detection system response is necessary to restore the specimen characteristic wave form closer to its true behavior. The convolution of data set in the time domain is a time consuming process which explains the benefit of using the frequency domain; as the convolution in time domain corresponds to multiplication in the frequency domain. This process requires the transformation of the time domain data to frequency domain data via Fast Fourier Transform (FFT). In the frequency domain the complex division of the Fourier transfer of the detection system output with frequency response function of the detection system shall provide the true complex input characteristic. This paper elaborates the methodology utilized for obtaining the Frequency Response Function (FRF) of the load detection system using digital Fourier analysis with a single input/output data set. This also emphasizes precautions and guidelines for improving results with FFT to obtain true FRF measurements of the load detection system. The FRF obtained is successfully used to identify the actual specimen wave form characteristic. This is achieved by extracting the structural response of the load detection system from the load cell output.

scholarly journals A Modal-Based Kalman Filter Approach and OSP Method for Structural Response Reconstruction

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Zhenrui Peng ◽  
Kangli Dong ◽  
Hong Yin
Keyword(s):  
Kalman Filter ◽  
Experimental Validation ◽  
Structural Response ◽  
Sequential Algorithm ◽  
Single Type ◽  
Acceleration Sensors ◽  
Response Reconstruction ◽  
Filter Approach ◽  
Displacement Reconstruction ◽  
Modal Method

The objective of the work is experimental validation and optimal experimental design for structural response reconstruction. A modal-based Kalman filter approach based on excitation identification Kalman filter is proposed for response reconstruction and excitation estimation of structures by using noisy acceleration and strain measurements. Firstly, different filters are introduced and discussed. Secondly, to avoid single type sensors, a displacement reconstruction based on modal method is introduced into the proposed approach. Thirdly, the backward sequential algorithm is given to obtain the optimal sensor locations. It is shown that the proposed method can avoid the divergency in the estimated process of excitation and displacements as a result of incomplete measurements. Reasonable estimates of strains, displacements, velocities, accelerations, and excitations of structures can be accomplished with few acceleration sensors and strain gauges.

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