scholarly journals Estimation of Evolutionary Spectra of Monitored Seismic Ground Motions by Transformation of Correlation Functions

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Zhifeng Xu ◽  
Li Li ◽  
Liang Hu
Keyword(s):  
Correlation Function ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Correlation Functions ◽  
Ground Motions ◽  
Engineering Structures ◽  
Power Spectral ◽  
Time Histories ◽  
Evolutionary Spectra ◽  
Sample Time

Spatially varying seismic ground motions recorded by distributed structural health monitoring systems (SHMS) can be used to improve the performances of civil engineering structures, necessitating estimation of the evolutionary power spectral density as an indispensable procedure for utilizing records of SHMS. This paper proposes a method for the estimation of evolutionary power spectral density of a nonstationary process by transforming the correlation functions of its sample time histories. First, the background of the theory of evolutionary power spectral density is reviewed in detail. Relationship between the EPSD and the correlation function of a reference stationary process is then established. Formulas are derived for estimating this correlation function directly from nonstationary sample time histories so that the EPSD can be obtained. The implementation procedure of the proposed method is also detailed. Finally, a numerical example is presented, which validates the proposed method, demonstrates its application for SHMS, and displays its capabilities by comparison with the traditional method.

scholarly journals Research on forest terrain roughness as a source of dynamic action on the vehicle

2017 ◽  
Vol 63 (No. 8) ◽  
pp. 363-369
Author(s):  
Mikleš Milan ◽  
Helexa Milan ◽  
Mikleš Juraj
Keyword(s):  
Correlation Function ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Ground Surface ◽  
Operating Conditions ◽  
Mobile Object ◽  
Object A ◽  
Power Spectral ◽  
Gneiss Granite ◽  
Ground Conditions

The issue of terrain conditions is very complex and its description is approached from different perspectives and with different objectives. Because it consists of the gathering of basic information for a mobile object, a wheeled forestry tractor, the terrain-vehicle approach was taken as the basis. Ground conditions are part of the operating conditions of wheeled forestry tractors. Uneven ground can be regarded as a source of vibration in the vehicle – towing truck. In this respect, given the random shape of the surface roughness, the solution to vibrations leads to a terrain correlation analysis in order to obtain a correlation function and power spectral density of the ground surface. Scanning of the ground micro-profile was performed using a device for quick terrain scanning, which from the mechanical aspect consists of a towing vehicle and a measuring carriage. Correlation function and power spectral density are the evaluation based on ground micro-profile measurements and the results of calculations. Measurements of forest terrain (road) micro-profile were done in the area of Little Fatra and Little Carpathians in Slovakia. In geological terms, the measurements were done in an area with the occurrence of gneiss, granite, limestone and flysch. No measurements were performed in a sandy area.

Development of Target Power Spectral Density Functions Compatible With Design Response Spectra

2015 ◽  
Author(s):  
Jinsuo R. Nie ◽  
Jim Xu ◽  
Joseph I. Braverman
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Seismic Analysis ◽  
General Procedure ◽  
Response Spectra ◽  
Acceleration Time ◽  
Power Spectral ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Spectral Shapes

For seismic analysis of nuclear structures, synthetic acceleration time histories are often required and are generated to envelop design response spectra following the U.S. Nuclear Regulatory Commission, Standard Review Plan (SRP) Section 3.7.1. It has been recognized that without an additional check of the power spectral density (PSD) functions, spectral matching alone may not ensure that synthetic acceleration time histories have adequate power over the frequency range of interest. The SRP Section 3.7.1 Appendix A provides a target PSD function for the Regulatory Guide 1.60 horizontal spectral shape. For other spectral shapes, additional guidance on developing the target PSD functions compatible with the design spectra is desired. This paper presents a general procedure for the development of target PSD functions for any practical design response spectral shapes, which has been incorporated into the recent SRP 3.7.1, Revision 4.

GENERATION OF UNIFORM HAZARD EARTHQUAKE ACCELEROGRAMS AND NEAR-FIELD GROUND MOTIONS

2012 ◽  
Vol 06 (02) ◽  
pp. 1250013 ◽  
Author(s):  
A. A. FATEMI ◽  
A. BAGHERI ◽  
G. GHODRATI AMIRI ◽  
M. GHAFORY-ASHTIANY
Keyword(s):  
Seismic Hazard ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Ground Motions ◽  
Near Field ◽  
Response Spectra ◽  
Geographic Region ◽  
Envelope Function ◽  
Power Spectral ◽  
Earthquake Accelerograms

The sets of records developed for the SAC Steel Project are classified according to the level of seismic hazard and specific geographic region, and have been used extensively for structural response and seismic hazard analyses. This study presents a parametric analysis of these record data sets for generation of uniform hazard earthquake and near-field records. The record parameters define far-field characteristics such as power spectral density and envelope function, and near-field effects such as acceleration pulse, power spectral density and envelope function. The proposed method for generation of near-field records uses the decomposing capabilities of wavelet transform on earthquake records. A set of uniform hazard earthquake accelerograms and near-field ground motions is generated based on the record parameters. The generated uniform hazard earthquake accelerograms representing a uniform level of seismic hazard for a particular geographic region involves seismic hazard studies, calibrated attenuation relationships, and local site amplification models. In order to assess the reliability and efficiency of the presented method, the statistical response spectra obtained from the generated accelerograms have been compared with those from the actual records. The obtained results showed that there is a good compatibility between the response spectra of the generated and actual records in the most of the frequencies.

Power Spectral Density and Cross Correlation Function Analysis of Finished Surface by Abrasive Jet with Grinding Wheel as Restraint

2009 ◽  
Vol 416 ◽  
pp. 300-305 ◽  
Author(s):  
Chang He Li ◽  
Ya Li Hou ◽  
Yu Cheng Ding ◽  
Bing Heng Lu
Keyword(s):  
Correlation Function ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Function Analysis ◽  
Grinding Wheel ◽  
Work Surface ◽  
Power Spectral ◽  
Finishing Process ◽  
Finished Surface ◽  
Precision Finishing

The abrasive jet finishing process with wheel as restraint is a kind of compound precision finishing process that combined grinding with abrasive jet machining, in which inject slurry of abrasive and liquid solvent to grinding zone between grinding wheel and work surface under no radial feed condition when workpiece grinding were accomplished. The abrasive particles are driven and energized by the rotating grinding wheel and liquid hydrodynamic pressure and increased slurry speed between grinding wheel and work surface to achieve micro removal finishing.In the paper,the finished surface morphology was studied using Scanning Electron Microscope (SEM) and microscope and microcosmic geometry parameters were measured with TALYSURF5 instrument respectively. According to the metrical results, the surface topographical characteristics were evaluated with correlation function and PSD (Power Spectral Density) of random process about machined surface before and after finishing. The results show that longitudinal geometry parameter values of finishing machining surface were diminished comparing with ground surface,and the mean ripple distance was decreased and, ripple and peak density were increased. Furthermore, the finished surface has little comparability compared to grinding machining surface.The isotropy surface and uniformity veins at parallel and perpendicular machining direction were attained by abrasive jet precision finishing with grinding wheel as restraint and the surface quality is improved obviously.

Damage Localization Based on Power Spectral Density Analysis

2007 ◽  
Vol 347 ◽  
pp. 589-594 ◽  
Author(s):  
Sheng En Fang ◽  
Ricardo Perera ◽  
Maria Consuelo Huerta
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Large Scale ◽  
Damage Identification ◽  
Random Excitation ◽  
Rc Beam ◽  
Engineering Structures ◽  
Damage Location ◽  
Power Spectral ◽  
Aluminum Beam

An environmental excitation having random characteristics may be more effective and cost-efficient than other excitation means for non-destructive damage identification purpose on most of the large-scale engineering structures under operation. In general, many existing damage indexes are constructed based on the modal properties derived firstly from the power spectral density (PSD) analysis of the structures under random excitation. However, the derivation procedures for the modal parameters usually introduce some extra errors into the indexes. This paper aims to propose a simple and feasible damage location index (DLI) constructed directly derived from the analysis results of the structural response PSD. The performance of DLI was verified using an aluminum beam with fixed ends and an experimental reinforced concrete (RC) beam under free boundary condition. Our results show that the damage location of the aluminum beam can be determined via the plot of DLI value by selecting the peaks with the amplitudes exceeding a predefined threshold value in both single- and multi-damaged scenarios. And the index may also predict the possible damage zones in the RC beam experimentally tested.

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