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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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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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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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