National Repository of Grey Literature 15 records found  1 - 10next  jump to record: Search took 0.01 seconds. 
Methodology of traditional working of construction timber for structural repairs of historical buildings
Kloiber, Michal ; Růžička, Petr ; Tippner, J. ; Kunecký, Jiří
The publication deals with a methodological description of traditional (manual) wood working for structural measures in repairs of historical buildings. The methodology includes the results of experimental testing performed during timber logging in various seasons (winter, spring, summer), results for different ways of working (cutting, splitting, hewing, and combination of hewing with floating), results of verifying the elimination of growth (residual) stresses in wood selection and working (selection of wood without natural defects and intentional interventions during working). The resulting methodology meets the protection standards of cultural heritage, in particular the requirement to minimize interference with the original material, while using the original working technology for newly incorporated elements including material selection. The methodology describes the prerequisites for use and the necessary marginal conditions, material selection, handling and storage of logs, woodworking technology (hewing, splitting, and cutting), but also storage of worked elements until the actual structural repair, while presenting the version of minimum interference with the original material using traditional (manual) working of timber on specific examples of structural elements.
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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).
Mechanical analysis of scarf joint fastened using cylindrical wooden dowel
Tippner, J. ; Milch, J. ; Kunecký, Jiří ; Kloiber, Michal ; Brabec, M. ; Sebera, V.
Traditional all-wooden woodworking joints play an important role in the behaviour of timber structures. These joints are also widely used when historically valuable constructions are being reconstructed and the connections are usually the masterpieces that testify to the high carpentry skills and knowledges of the overall mechanical behaviour. Within historical timber structures traditional carpentry joints were used while wooden dowel fixed mutual position of elements. Main aim of this study was to contribute to knowledge base about prediction and analysis of the mechanical performance of frequently used scarf joints made from spruce wood fastened using oak dowels. The objectives were to determine the joints' slip moduli and load-carrying capacity by means of theoretical and experimental approaches, in next to assess the mechanical behaviour of dowels through experimental investigation, and finally to perform a strain analysis of dowels. For these purposes, the optical technique employing three-dimensional full-field digital image correlation was used. The experiments were done on the full-scale specimens meeting the requirements of European standards (EN 383 and EN 26891), which were made from Norway spruce (Picea abies L. Karst.) and English oak (Quercus robur L.). The mechanical load consisted in tensile parallel and perpendicular to grain direction within the main components. The results of this study showed good correlation between theoretical approach based on based on Beam on Elastic Foundation theory and European yield model theory and experimental observations.
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.
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.
Lapped scarf joints for reconstruction of historical structures
Kunecký, Jiří ; Fajman, P. ; Hasníková, Hana ; Kuklík, P. ; Kloiber, Michal ; Sebera, V. ; Tippner, J.
This paper presents a description of the repair of timber structures using a prosthesis scarf\njoint designed for the replacement of damaged parts of beams. This new scarf joint makes use\nof the strutting effect of inclined contact faces where the forces are transmitted through\nwooden coupling elements - wooden dowels or keys. The scarf can be modified in four\nvariants according to the relevant stress and is suitable for historically valuable timber\nstructures. It meets both functional and aesthetic requirements. The designer - structural\nengineer will learn in the methods the load bearing capacity or stiffness of the beam with the\ndesigned joint, its recommended dimensions and detailed geometry. The contractor will\nappreciate the description of the execution and maintenance of the joint.
The use of carpentry joints for the repair of historical structures
Kloiber, Michal ; Kunecký, Jiří ; Hasníková, Hana ; Sebera, V. ; Tippner, J. ; Fajman, P. ; Růžička, P. ; Stejskal, D.
The conservation process describes the way of using prosthesis lap scarf carpentry joints for reconstruction of historical timber structures. This new scarf joint makes use of the strutting effect of inclined contact faces where the forces are transmitted through wooden coupling elements - wooden dowels or keys. The process consists of several chapters describing the diagnostics of original wood and the repaired structure, the design of the joint and execution of the joint. It also includes examples of succesful reconstruction made with according to this conservation process.
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Plný tet: 0459383_2015_Kloiber_et_al_Vyuziti_celodrevenych_tesarskych_spoju_pri_opravach_historickych_konstrukci_PP_NAKI-004_AVV - Download fulltextPDF
Lapped scarf joints for repairs of historical structures
Kunecký, Jiří ; Fajman, P. ; Hasníková, Hana ; Kuklík, P. ; Kloiber, Michal ; Sebera, V. ; Tippner, J.
This guideline presents a description of the repair of timber structures using a prosthesis scarf joint designed for the replacement of damaged parts of beams. This new scarf joint makes use of the strutting effect of inclined contact faces where the forces are transmitted through wooden coupling elements - wooden dowels or keys. The scarf can be modified in four variants according to the relevant stress and is suitable for historically valuable timber structures. It meets both functional and aesthetic requirements. The designer - structural engineer will learn in the methods the load bearing capacity or stiffness of the beam with the designed joint, its recommended dimensions and detailed geometry. The contractor will appreciate the description of the execution and maintenance of the joint.
Fulltext: content.csg - Download fulltextPDF
Plný tet: 0459382_2016_Kunecky_et_al_Celodrevene_platove_spoje_pro_opravy_historickych_konstrukci - Download fulltextPDF
Designing of all-wooden carpentry joints for reconstruction of historical structures
Kunecký, Jiří ; Hasníková, Hana ; Fajman, P. ; Tippner, J.
The article introduces the new method „Lapped Scarf Joints for Repairs of Historical Structures“ that deals with the design of the lapped scarf joint suitable for the reconstruction of valuable historical timber structures, with help of making the prosthesis for the damaged parts of the beams. The method is the result of the four-year research project supported by the Czech Ministry of Culture within NAKI program. Institute of Theoretical and Applied Mechanics AS CR, Faculty of Civil Engineering CTU and Faculty of Forestry and Wood Technology of Mendel University participated on the research.

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