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Souhrnná výzkumná zpráva z měření vibrací v objektu ELI Beamlines
Pospíšil, Stanislav ; Bayer, Jan ; Hračov, Stanislav ; Urushadze, Shota
Souhrnná zpráva popisuje postupy a výsledky série měření mikro-vibrací podlah a stěn laserových hal v objektu ELI. Úroveň změřených vibrací konstrukcí je posouzena s ohledem na kritéria NIST, která se aplikují pouze prostory s nejpřísnějšími vibračními požadavky. Speciální pozornost je zaměřena také na zhodnocení různých úprav podlah provedených lokálně, ve vybraných místech. Tyto úpravy byly realizovány za účelem snížení hladiny vibrací i z krátkodobého hlediska, které klientem zvolená metodika posouzení nepostihovala.
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Proposal for loading tests of bridges - simulation and laboratory experiments
Bayer, Jan ; Urushadze, Shota ; Černý, Miloš
A new dynamic load testing of bridges is proposed and theoretically investigated. A transient analysis of passing vehicle over a bridge in ANSYS and an analytical program in MATLAB for the transient solution of piecewise linear mechanical structures were developed to assess the effects of the proposed dynamic load on a bridge model. According to the first laboratory experiments, it seems that the proposed travelling impulse load could surpass some of the shortcomings and limitations of the currently applied methods of bridge testing. The investigation is a part of a project aimed at drive-by identification of dynamic properties of bridges and further experimental and analytical research will follow.
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A concept for testing and monitoring of building structures – theoretical case study
Bayer, Jan
A mere comparison of measured and analytical deformations, natural frequencies and mode\nshapes provides us with just a small part of the information contained in the data, especially when component- level damage prevention is needed. The presented analysis studies in detail a few criteria for evaluation of measured data, with the example of simulated plane trusses in respect to the ultimate limit state. It demonstrates the high potential of a systematic approach, while combining several criteria, particularly when using simultaneous strain and deformation measurements, as it documents the proposed Relative Mode Difference (RMD) criterion. On the other hand, the study points out the major limitation of practical applications that is caused by unknown inherent uncertainties of various kinds, providing us with the incentive for further experimental research.
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Health monitoring of building structures: preliminary considerations on a case study
Bayer, Jan ; Urushadze, Shota ; Zíma, Pavel
Ageing, erosion, local damage or increase of the operating loads can decrease the reliability and load bearing capacity of building structures. Vibration monitoring may provide a promising solution of this problem, however robust health monitoring techniques are needed before wider practical applications. The presented analytical and experimental case study on a simple supported steel beam is an introductory practical investigation into this topic. It shows the sensitivity of chosen parameters to artificially induced damage and outlines possible directions or further research in conclusions. Special attention is paid to simultaneous monitoring of deformations and strains which can provide us with a useful information about the stress redistribution in monitored or tested structures.
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Changes of dynamic properties of a timber frame due to simulated seismic load: a case study
Bayer, Jan ; Pospíšil, Stanislav ; Urushadze, Shota ; Kasal, B.
The data from a laboratory seismic resistance test of a three-story timber frame stiffened with steel joints were used to compare sweep and random excitation techniques on the platform of experimental modal analysis. The changes of mechanical properties due to increasing seismic load of the timber structure are demonstrated on corresponding changes of vibration modes and on changes of averaged frequency response functions. The comparison of averaged frequency response functions turned out to be at least as efficient tool for damage indication as the comparison of modal properties in this case. The experiences obtained in this case study are aimed at increasing the efficiency of dynamic tests and methods of Structural Health Monitoring.
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