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A new device for determining the mechanical properties of wood
Kloiber, Michal ; Drdácký, Miloš
The paper presents a novel concept of a diagnostic tool for "in-situ" assessment of the mechanical characteristics of wood in a prepared 12 mm hole. The device enables direct determination of conventional strength and modul of deformation in arbitrary depth along timber profile .The aim was to verify the measurement results of the new device with measurements on already tested devices according to european standards. Experimental tests show above all a very good correlation between conventional strength by means of the new device and standard samples strength in pressure along the fibers. This semi-destructive method causes a very gentle damage and can be used for the assessmen of historic timber structures.
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Reconstruction of a Baroque Open Beam Ceiling Based on Material Analysis
Kloiber, Michal ; Válek, Jan ; Bláha, Jiří ; Čechová, J.
Reconstruction of a ceiling in the north-eastern wing of a former water fortress in Jeseník was carried out during the repair of its roof structure and replacement of the roof. The most damaged parts of the bearing ceiling beams were removed and partially replaced with new timber in the 70s of the 20th C. The way the work was carried out corresponded to the methods and approaches of the cultural heritage protection of that time. The replacement of damaged heads of ceiling beams with new timber that was fitted without connection to the original ceiling beams and only simply hanged on a metal girder can be considered highly provisional from the current perspective. That is why the repair of timber structures of the water fortress included also a reconstruction of the original ceiling system.
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Reconstruction of a Baroque Open Beam Ceiling based on Material Analysis
Kloiber, Michal ; Válek, Jan ; Bláha, Jiří ; Čechová, J.
Reconstruction of a ceiling in the north-eastern wing of a former water fortress in Jeseník was carried out during the repair of its roof structure and replacement of the roof. The most damaged parts of the bearing ceiling beams were removed and partially replaced with new timber in the 70s of the 20th C. The way the work was carried out corresponded to the methods and approaches of the cultural heritage protection of that time. The replacement of damaged heads of ceiling beams with new timber that was fitted without connection to the original ceiling beams and only simply hanged on a metal girder can be considered highly provisional from the current perspective. That is why the repair of timber structures of the water fortress included also a reconstruction of the original ceiling system.
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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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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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The effect of chemical degradation of surface layers on mechanical properties of wood
Drdácký, Miloš ; Kloiber, Michal ; Frankl, Jiří ; Bryscejn, Jan ; Tippner, J.
The aim of the research was the determination of the effect of chemical degradation on the surface layers of wooden constructional elements and their mechanical properties and also the depth which the damage reaches. The degradation of wood surface layers was caused by chemical reactions of some compounds contained within fire-prevention coatings applied repeatedly on wooden constructions of historic buildings in the past. These include e.g. ammonium sulphate and ammonium phosphate. This paper presents experimental procedures and results obtained through measuring of mechanical properties in the damaged layer of fibrillated wood and in wood without damage. The observed properties were wood compressive and tensile strength and wood hardness. The results proved a loss in cohesion and changes in mechanical properties only in a thin surface layer.
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Portable Testing Device for In-situ Testing of Building Material
Vavřík, Daniel ; Jandejsek, Ivan
Examination of brittle buildings materials using mechanical tests requires sampling of studied elements and materials (stones, bricks or concrete). In case of existing integral structures the best suitable sampling method is core drilling. It is preferred to test samples in situ in all cases where it is possible to avoid changes of the material properties during transportation and storing. Moreover it is possible to prepare other samples operationally wen some uncertainty occurred if in situ testing is possible. For such a purpose, a portable testing device has been designed and manufactured. This device is primary devoted for so called split test technique which is based on well know testing of Brazilian disk. Analytical equation used for evaluation of the split test is based on several assumptions which have to be verified. For such verification Digital Image Correlation technique was used in our work.
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