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Longitudinal log splitting in repairs of timber structures
Kloiber, Michal ; Hrivnák, Jaroslav ; Bryol, R. ; Tippner, J.
The range of technologies used has lacked a description of the traditional longitudinal log splitting, which was often used in order to utilize the maximum possible volume of timber extracted for constructions (especially rural timbered buildings). Longitudinal splitting supports carpentry sustainability as well as allows for accurate replication of the original elements (in dimension, shape, technology). Therefore, the research focused on the design of a procedure practically usable and applicable in the common practice for repairs of timber structures, especially historical monuments. Such a procedure is longitudinal splitting using wedges (metal and wooden) and mallets. The aim of the heritage conservation procedure was to practically describe the technical solution, the technological procedure of longitudinal log splitting allowing the use of hand tools only. The procedure respects the protection of cultural heritage standards, in particular the requirement to minimize interference with the original material, while retaining high accuracy of reproduction of the original properties of structural elements.
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Creep behavior of oak pegs under tension in dry and wet conditions
Kunecký, Jiří ; Kloiber, Michal ; Hasníková, Hana ; Hrivnák, Jaroslav ; Sebera, V. ; Tippner, J. ; Milch, J.
Carpentry joints equipped with oak pegs are well suited for applications where increased moisture is not a significant factor. However, for the use in outside conditions, e.g. in the repairs of historical timber bridges, the pegs connecting the two halves of the joint may deform and change their original shape. This happens especially during long-term loading and can be augmented significantly by environmental changes. Creep behavior can play a crucial role for some types of carpentry joints, especially when precise contacts of faces in the joint are required. The paper deals with experimental testing of creep behavior of 16 mm oak pegs under dry and wet conditions loaded by the combination of shear and bending between two planks made of spruce in the direction parallel to grain. The results show that the decrease of theoretical stiffness values over time plays a significant role in the force redistribution in the joint especially due to moisture effects (drop 50-70% of the original stiffness).
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The Cloak Bridge in Český Krumlov – measuring of mechanical properties
Kloiber, Michal ; Sebera, V. ; Hrivnák, Jaroslav ; Tippner, J. ; Kunecký, Jiří
Timber bridges are often exposed to harsh conditions of the environment. The exposure of the timber structure often leads to its deterioration. Standard test procedures to determine typical properties of wood cannot be used as there is the requirement of the minimum interference with the structure. Several non-destructive testing (NDT) methods for the determination of timber condition have been developed and are used. However, the results of NDT can be used to predict mechanical properties of timber elements only to a limited degree. Semi-destructive testing (SDT) methods are a compromise. In the paper a functional model of a device that allows for the measurement of conventional strength and modulus of deformation of timber in compression parallel to the grain is presented. The device is inserted to a bored hole and pushes the jaws apart with a small test jack loading the bore walls. This paper presents possible use of the device for surveys of timber bridges.
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Analysis of mini-jack technique for in situ measurement of strength
Kloiber, Michal ; Tippner, J. ; Kunecký, Jiří ; Sebera, V. ; Milch, J. ; Hrivnák, Jaroslav
The paper presents a recently developed diagnostic technique for in situ determination of modulus of deformability (MODL) and conventional strength (CSL) parallel to the grain using the mini-jack inserted in bored hole. The mini-jack compression technique simulates the standard compression test, it is compared to that to examine its prediction strength (correlation coefficients). The paper shows an influence of moisture content of wood on experimental measurements using this technique. The measurement was carried out at spruce samples at three moisture contents of 12, 18 and 24%. The results of the tests prove a very good correlation of the strength determined by the proposed technique and wood density and strength determined at universal testing machine in compression parallel to the grain. The effect of the moisture content on the measurement by the mini-jack technique was proved to be significant. Beside that, the newly-developed instrument was also studied using digital image correlation (DIC) technique to analyze induced strains around the bored hole. This was studied on halved spruce samples. The DIC revealed symmetric character of the loading and significant differences between strains induced in tangential and longitudinal directions.
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Survey report: Construction and technical assessment of the state of timber, trace analysis and surveying of a timbered barn in Skalička 3
Kloiber, Michal ; Růžička, Petr ; Buzek, Jaroslav ; Hrivnák, Jaroslav ; Bláha, Jiří
Surveys whose aggregate output is this survey report included the determination of the extent of damage to the timber, surveying, and trace analysis of the original craftsman working of a timbered barn belonging to house no. 3 in the village of Skalička u Hranic, which is located in the Přerov district in the Moravian region called Pobečví. The report has been drawn in response to the demand by the Wallachian Open Air Museum located in Rožnov pod Radhoštěm, which contained a request to diagnose the timber elements using NDT devices and carry out their trace analysis. The findings will contribute to a qualified assessment and proposal of a harmless transfer of this unique timbered building.
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Survey report on the condition assessment of the Church of the Holy Spirit truss in Telč
Kloiber, Michal ; Bláha, Jiří ; Hrivnák, Jaroslav ; Buzek, Jaroslav ; Kunecký, Jiří ; Hasníková, Hana
The survey described in this report contains the condition assessment of the truss of the Church of Holy Spirit in Telč. The stimulus for the survey report was an order from the parochial congregation ČCE in Telč. The order included a request to assess the condition and identify the extent of wood-decaying damage to the truss of the Church of the Holy Spirit in Telč, focusing on the location of the critical spots, the classification of the damage degree, the determination of the extent of hidden damage using non-destructive devices, and the specification of the wood damage cause, including drawing of the results in the documentation on the current truss condition. Based on the results, specific procedures of repair measures were proposed and the elements proposed for the reconstruction were sketched in the documentation.
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Survey report on the assessment of the condition and measurement of mechanical properties of a timber ceiling structure in Müller House, Komenského náměstí no. 1, Opava
Kloiber, Michal ; Hrivnák, Jaroslav ; Buzek, Jaroslav
The survey described in this survey report contains the assessment of physical and mechanical properties of ceiling beams including false ceiling of the Müller House, Komenského náměstí no. 1, Opava. The impulse for this report was an order submitted by the Statutory City Opava with headquarters in Horní náměstí 69, Opava. The order included a request to assess the condition of timber elements (location of damaged places and the classification of the damage degree, location of hidden damage to ceiling beam ends using non-destructive devices), which can contribute to the assessment and design of a gentle renovation of the historically valuable building structure. \n
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Research Report on Condition Assessment of Wood-destroying Damage to Log Walls of a Landless Person's Cottage of Leskovec (orig. No. 70) and a Cottage of Lužná (orig. No. 28) now in the Museum in Rožnov pod Radhoštěm
Kloiber, Michal ; Hrivnák, Jaroslav ; Bláha, Jiří
The subject of the research report was to assess the condition of and identify the wood-destroying damage to the walls of a landless person's cottage of Leskovec and a cottage of Lužná, two log structures that are part of the exhibition at the Wallachian Museum in Rožnov pod Radhoštěm. The report focused on locating 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 (mycological damage) or insect attack (entomological damage) and drawing the results obtained in the plan documentation. The report was based on direct and mediated visual observation using an endoscope and mainly on measurements taken using a resistance microdrilling device and also on ascertainment of mechanical properties of wood using expanding jaws in the borehole. Based on the results, specific procedures for rehabilitation measures were designed and elements designed for structural rehabilitation were marked in the drawing documentation.
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