Direct comparisons between SIMO and out-put only results were not presented in this paper because of a significant time lapse between the SIMO testing and collection of the presented output-only data. However, a review of frequency data indicates a significant difference in extracted frequencies between the SIMO results and the output-only results. This difference is attributed to two possible causes. The first is a break-in of the structural system resulting from several months of traffic on the structure before collection of the output-only data presented here. The second possible cause is the mass effect of traffic on the structure during collection of the output-only data. Although not presented here MACs between SIMO and output-only mode shapes were lower than those between similar output-only modes indicating some difference in extracted mode shapes. Several conclusions can be drawn from the results presented in this paper. 1. The analytic, SIMO, and output-only methods returned similar modal properties for six lower modes indicating that good correlation should be expected between detailed analytic models and experimentally derived properties of the real structure. 2. The SIMO and implemented output-only method had similar difficulty in accurately and consistently identifying several closely spaced modes More data may improve the results of both methods 3. Output-only results exhibited lower extracted natural frequencies than SIMO testing. 4. For the structure under test, fluctuation of extracted modal frequencies of approximately 1.9% should be expected. The mode shapes for well-defined frequencies showed very good repeatability. 5. Variations in mode shapes appear to be smaller than the corresponding changes in modal frequency. 6. The datasets consisting of 60 to 100 vehicular impact events used in the presented output-only calculations provided good repeatability of extracted properties.
Implementation of ambient response monitoring instrumentation for a bridge assessment test bed
Implementierung einer Geräteausrüstung zum Umgebungs-Frequenzgang-Monitoring für einen Brückenbewertungsprüfstand
2005
11 Seiten, 10 Bilder, 14 Tabellen, 22 Quellen
Aufsatz (Konferenz)
Englisch
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