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Research Report on Condition Assessment of the Holy Ghost Tower's Roof Frame in Telč
Bláha, Jiří ; Kloiber, Michal ; Frankl, Jiří ; Buzek, Jaroslav
The subject of the research report was to assess the condition of and identify the range of wood-destroying damage to the roof frame of the Holy Ghost tower in Telč focused on locating critical points, classifying the degree of damage, determining the extent of concealed attack by the means of non-destructive devices, specifying whether wood is subject to a fungal attack (mycology) or insect attack (entomology), including the drawing of the results obtained in the drawing documentation of the existing condition of the roof frame. Based on the results, specific procedures for rehabilitation measures were designed and elements designed for structural rehabilitation were included in the drawing documentation. The report is based primarily on direct and mediated (endoscopic) visual observations supplemented by measurements using a resistance microdrilling device.
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Characteristics of Damage to the Structural Element by Creating its "Degradation Profile"
Frankl, Jiří
This paper presents results of experimental establishment of the extent of damage and changes in strength of a wooden structural element (a rafter base) through the creation of its -degradation profile. The tested part of the structural element was divided into segments by the means of a regular network from which standard test specimens were made with dimensions of 20x20x30 mm on which strength tests under compression along the fibres of wood were carried out. Readings were divided, according to the decrease in the property observed against the values of healthy (undamaged) wood, into 4 quality groups and then transferred back to the network of segments. A graphic model description of the shape and course of degradation of wood caused by wood-destroying fungi was created, marked as the - degradation profile of an element.
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Changes in physical properties of wood damaged by activities of wood damaging fungi
Frankl, Jiří
Abstract: This paper presents results of experimental, laboratory establishment of the extent of changes in physical properties (swelling, water absorbability) of timber (spruce) damaged by the activity of wood-damaging fungi. The experiment was carried out using standard test samples (20 x 20 x 30 mm) prepared from new timber and subsequently exposed to the activities of wood-damaging fungi (Serpula lacrymans, Trametes versicolor) under optimal growth conditions for the period of 15 to 60 days. Changes in physical properties were observed in the damaged samples as per the CSN 490126 and CSN 490104 Czech National Standards. The experiment proved significant changes in the observed properties depending on the fungi type and duration of the activity thereof.
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Determining the quality condition of structural wooden components during structural-technical surveys of buildings
Frankl, Jiří
For quality and efficient rehabilitation or reconstruction of structural wooden elements, it is necessary, before starting, to make as detailed survey as possible to determine their quality condition. Especially with regard to damage caused by wood-damaging biological agents. The paper presents suitable procedures to be applied in order to prepare the building, wooden structures as well as individual structural elements (prior to making the survey). Survey methods, applicable to individual structural elements and the structure as a whole (both sensory and instrumental) and outputs - information that can be obtained prior to the commencement of the reconstructions about the quality condition of wooden structures. Various procedures and methods are demonstrated on examples from surveys of various types of buildings.
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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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