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Improved precision of stereometric measurement of relief's surface by means of structured light enhanced photometric stereo method
Valach, Jaroslav ; Bryscejn, Jan
Photometry is an interesting method for 3D measurement of surfaces with relief. It utilizes a relationship between depth of shadow determined intensity of light and surface normal orientation towards source of light. Advantage of methods incorporating this principle is their independence on distance between measured object and the measuring apparatus and scalable sensitivity suitable for relatively flat surfaces. On the other hand, there is a drawback as the photometric methods yield results up to an unknown multiplicative factor. One way how to overcome this limitation is to simultaneously describe the measured surface by means of another optical method. Among the -candidates-, the structured light projection is the most promising one for a simple implementation. The presentation of the possibility to integrate these two methods in unified system is main topic of this contribution.
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Operation Test of a New Experimental Technology for Research of Lateral Pressure
Koudelka, Petr ; Valach, Jaroslav ; Bryscejn, Jan
Hardware and software accessories of a original advanced experimental equipment was finished and debugged at the beginning of the last year. The equipment was constructed for a basic research of lateral pressure multi-phase granular materials and to verify a theoretically derived -General Lateral Pressure Theory- (GLPT). A number of technical tests of measuring components and computer controlling system were performed before the finish of the equipment development. Several quasi-experiments without a sample ended the equipment preparation at last. The first real experiment E5/0,2 with pressure at rest and passive pressure was used for an operation test of the new equipment. The paper deals the experimental technology (apparatuses, hardware, software, etc.) and experiences of them during an extremely slow movement of front wall. Also, it is mentioned a visual monitoring, 3D scan technology including.
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Analysis of mortar used for grouting of enclosure wall of St. Wenceslas church in Chlum near Třebíč
Slížková, Zuzana ; Drdácký, Miloš ; Hauková, Petra ; Frankeová, Dita ; Janotová, Dana ; Niedoba, Krzysztof ; Zeman, Antonín
Investor of building (Roman Catholic parish) asked ITAM AV ČR, v.v.i. for an analysis of wall mortar of the St. Wenceslas church in Chlum. The reason for this investigation carried out was the fact that the mortar applied to the wall in 2010 shows after winter disturbances, which reflected a lack of cohesion and adhesion of mortar to the substrate. The mortar is crumbling in many places, sometimes its fragments fall off. The investor asked for an analysis of the composition of applied mortar and the assessment of the suitability of materials for the construction.
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Measurement of Water Uptake of Historic Surfaces-State of the Art Review
Zíma, Pavel
In situ testing of material water uptake represents one of very basic and indispensable techniques in the conservation practice aiming different purposes. Water uptake of porous building materials used on historical constructions significantly correlated to some other materials characteristics. Capillary properties of porous materials can be measured by means of Karsten tube and modified tools of methods. A pilot prototype of one of them has been developed and tested in ITAM AS CR for measuring water absorption under low pressure. The device has output connector for linking to a computer and reading the stored data. The device was tested in laboratory as well as in situ for a basic performance. The acquired data were evaluated using software specially writen for this purpose in MatLab.
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Diagnostic methods for evaluation of construction timber
Heřmánková, V. ; Kloiber, Michal ; Tippner, J. ; Anton, O.
In the present time, there is an effort in the Czech Republic to increase the share of realization of wooden structures. For this reason the necessity to pay higher attention to wood as building material, to learn how to inspect its quality before starting the building as well as of the already bulit-in wood is evident. The paper performs diagnostic methods for evaluation of construction timber being used at the workplaces of the authors. The methods are sorted according to the kind of invasiveness onto non-destructive, semi-destructive and destructive.
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Analysis of eigen-values of viscously damped two degrees of freedom system due to changes of parameters of secondary subsystem
Hračov, Stanislav ; Náprstek, Jiří ; Pospíšil, Stanislav
The paper deals with an analysis of non-classically damped two degrees of freedom system from the point of view of eigen-values. The theoretical relations between the system parameters for the case of multiple complex eigen-values were derived. The parametric problem was carried out analytically and graphically. The influence of the relative frequency tuning on the overdamping of individual eigen-values with increasing of the secondary damping was studied. The overdamping intervals were defined with respect to the mass ratio and the frequency tuning. The boundaries between respective overdamping intervals represent among others the frequency tuning of system with multiple complex eigen-values. The phase between components of eigen-modes and its relation to the eigen-values were examined with respect to the secondary damping increase.
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Brifag - the EU project on the bridge fatigue
Frýba, Ladislav
The main objective of the project is to study the whole -fatigue life- of the test girder, from the initiation of the first fatigue crack to the complete fatigue failure of the whole girder. In so doing, the growth of all fatigue cracks generated in the breathing web is measured and their impact on the girder collapse mechanism studied. Some characteristic results are presented.
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Multipurpose experimental rig for aeroelastic tests of bridge girders and slender beams
Pospíšil, Stanislav ; Král, Radomil ; Náprstek, Jiří
The bridges, footbridges and broadcast towers create an important subset of infrastructure subjected to dynamic loading of various origins. Especially, exposed to wind, they are susceptible to vibrations under certain circumstances due to pure load action or aero-elastic effects. This means that once an element or a structure starts to vibrate, a complex interaction between the moving boundary and the airflow takes place. Because of the complexity, the research has been in progress for several decades in both theoretical and experimental way. The article describes an original and multi-purpose experimental frame for the analysis of complex linear and non-linear aspects of aero-elastic behavior of the slender beams. The apparatus meets the rigorous theoretical assumptions and allows very precise and quick adjustment of the stiffness and mass of the structure, which is not always possible with a traditional "parallel spring-supported bridge" approach used by many researchers.
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Dynamics of a vibration damperworking on a principle of a heavy ball rolling inside a spherical dish
Náprstek, Jiří ; Fischer, Cyril ; Pirner, Miroš
Wind excited vibrations of slender structures such as towers, masts or certain types of bridges can be reduced using passive or active vibration absorbers. If there is available only a limited vertical space to install such a device, a ball type of absorber can be recommended. In general, it is a semispherical horizontal dish in which a ball of a smaller diameter is rolling. Ratio of both diameters, mass of the rolling ball, quality of contact surfaces and other parameters should correspond with characteristics of the structure. The ball absorber is modeled as a holonomous system. Using Lagrange equations of the second type, governing non-linear differential system is carried out. The solution procedure combines analytical and numerical processes. As the main tool for dynamic stability investigation the 2nd Lyapunov method is used. The function and effectiveness of the absorber identical with those installed at the existing TV towers was examined in the laboratory.
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