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New devices for diagnostics of historical structures
Hasníková, Hana ; Kloiber, Michal ; Zíma, Pavel
The aim of the paper is to present a few new devices that were developed at ITAM AS CR for non-destructive testing of materials, especially those from historically valuable structures. So called microtube is a semi-automatic portable tool for water absorption measurements. It consists of box with microprocessor where the time is recorded and the plastic “pistol” – a part that is in contact with the material surface and where the scaled micro-tube is fixed on. The natural stones, mortars and other porous materials can be measured by the microtube; it is very useful to assess the efficiency of various hydrophobic treatments used within the restoration. The diagnostic device for in-situ assessment of timber in existing structures enables direct determination of conventional compressive strength and modulus of deformability in arbitrary depth along timber profile. The semi-destructive method causes a very gentle damage on the structural members.
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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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Analysis of wood behaviour in the surroundings of a pin being pushed for the diagnostics of constructional elements of buildings
Kloiber, Michal ; Tippner, J. ; Hrivnák, J. ; Vichrová, Gábina ; Valach, Jaroslav
The technical solution of this diagnostic device for in-situ and laboratory measuring of conventional strength and the module of deformation by opening clamps in a drilled hole belongs to the field of quality and material property testing, especially concerning timber. In dependence on the specific technical solution, the device can be used for an establishment of conventional strength and the module of deformation of any material by opening clamps in a drilled hole in the examined volume. It also finds application in the situations when resistance drilling cannot be used and the mechanical properties of timber need to be established through the entire section of the examined element. Its main advantages are its speed and simple operation without a need for power distribution network.
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Influence of geometric parameters on the stiffness of traditional dovetail timber joint
Kunecký, Jiří ; Cacciotti, Riccardo ; Kloiber, Michal
The paper presents the development of numerical modeling for a traditional dovetail timber joint. The objective is to find the influence of its geometrical properties on the mechanical stiffness of the joint as well as to assess the main problems and limitations faced during the numerical modeling of the structure. An experiment with a replicated timber joint was used to validate the model. Material properties were ascertained and contact adjustment was made. Parametric study was performed: two angles of the joint beams were varied. Suitable ranges of the angles for each type of loading were found. Main limitations and problems present in the modeling are depicted in the discussion.
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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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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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