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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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Assessment of vibrations in museum's environment
Valach, Jaroslav ; Wolf, Benjamin ; Paulová, E. ; Urushadze, Shota
This paper deals with measurement of mechanical vibrations and accelerations threatening objects in museum collections. Two case studies are presented. The first case analyses situation in museum exhibitions strongly influenced by street traffic in its close proximity. It compares results obtained by sensitive professional measurement system to the custom-built user device for acceleration recording. The second case analyzes object’s accelerations during transport based on measurement by the custom-built device.
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Problémy spojené s užitím lamelových pásnic u ocelových mostů
Křístek, V. ; Kunrt, J. ; Škaloud, Miroslav ; Urushadze, Shota
Problematika lamelových pásnic nabývá v poslední době důležitosti mezi konstruktéry ocelových mostních konstrukcí, zejména proto, že umožňuje vyhnout se při návrhu velmi silným přírubovým deskám. Tento názor je založen na předpokladu, že lamely jsou dokonale rovinné a jsou v dokonalém vzájemném kontaktu v celé své ploše, což znamená, že zatížení se přenáší prostým tlakem a že plné spolupůsobení obou lamel je plně realizováno smykovým tokem v obvodových koutových svarech, spojujících obě lamely. Ve skutečnosti však tento předpoklad není nikdy dodržen: není v možnostech reálné výroby ocelových konstrukcí zajistit, aby lamely (jako ocelové desky) byly perfektně rovinné; jsou vždy počátečně zakřiveny a potom vždy dochází k zatlačování vrchní lamely do mezery, jež vzniká kombinací nevyhnutelných počátečních zakřivení obou lamel. Potom pod mnohonásobně opakovaným zatížením vozidly, dochází k mnohonásobně opakovanému ohybu zatlačované lamely ( můžeme říci, že lamela "dýchá"), tedy ke kumulaci poškození. Tento příspěvek popisuje výsledky výzkumu prokazujícího, že jev dýchání lamel může výrazně omezit životnost konstrukce.
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Breathing-induced fatigue in thin-walled steel bridge construction
Škaloud, Miroslav ; Zörnerová, Marie ; Urushadze, Shota
Several years ago, the authors started an experimental investigation into the breathing phenomenon of the webs of thin-walled steel girders , which to date comprised more than two hundred tests. The cumulative damage behaviour generated by web breathing was analysed, the process of the initiation and propagation of fatigue cracks induced thereby was studied, and their impact on the failure mechanism and the fatigue limit state of the girders was determined. And, to conclude, a recommendation for design, taking account of the aforesaid, was established.
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Seismic performance of timber frames
Pospíšil, Stanislav ; Urushadze, Shota ; Koleš, Jan
A series of dynamic experiments was performed on one-story timber frame. In comparison with the previous frames [1, 2], improved connection between column and girder was used here. The tests included sinusoidal sweeps in two directions, arbitrary signals simulation earthquake loads in three directions, and snapback tests. Various parameters were measured, for example tension on columns and slabs, rotation between columns and beams, displacement of columns and acceleration of columns and beams. All these parameters lead to classification of the frame behavior with designed type of connection, for example the natural frequencies, eigenmodes and other dynamical properties of the structure. Parameter description will allow us to design and improve mathematical model of the timber frame.
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Investigation of composite material degradation indicators using acoustic measurement: comparison with laser vibrometry
Fíla, Tomáš ; Urushadze, Shota ; Kytýř, Daniel ; Valach, Jaroslav ; Šperl, Martin
This paper deals with investigation of acoustic material degradation indicator (attenuation decrement drop of selected natural frequency) measured by a custom-built experimental device. Samples of C/PPS fibre composite material were analyzed. Acoustic signals were recorded and processed using spectral analysis and sound signal regression. Data measured by this method were verified by comparative experiment. Specimens were simultaneously measured using both acoustic experimental device and laser vibrometer. Modal analysis of the specimen were carried out prior to the experiment. This enabled assessment of specimens natural modes and therefore the best impact zone. In total, 10 measurements were performed for each specimen at the same level of degradation. Measured data were then processed and compared. The specimens were repetitively measured after designated number of loading cycles.
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Cyclic loading of masonry walls and its anti seismic reinforcing
Wünsche, Martin ; Hračov, Stanislav ; Pospíšil, Stanislav ; Urushadze, Shota
The damage of structural masonry walls is one of the most widespread harming injuries and cause of loss of serviceability and seismic capacity for a building. Therefore a research into possibilities which would improve these characteristics have been carried out within the 7th EC Framework programme project NIKER. The retrofitting approach is constrained by conservation requirements of minimum interventions which should not severely change the structural behavior and the structural appearance, and should prefer solutions without a necessity of total structural disassembling. This artikle provides an overview about the research that led to applications of the steel wire ropes and geo-nets ontoadobe brick walls.
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