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Analytical model of joint loaded perpendicular to wooden grain
Hataj, M. ; Pošta, J. ; Hasníková, Hana ; Kunecký, Jiří
Computing models for structural behaviour and determination of traditional timber butt joints using analytical relations are presented in this paper. A component method is the base of the computing technique introduced herein. This method is usually used for steel joint design. The component method is based on dividing a joint into individual components. These are defined by partial joint component stiffness. An analytical solution includes a subsidence effect of wooden material close to compressive loading. Analytical computation results are compared with the experimental outputs. A design procedure according to Eurocode 5 for a load capacity determination of perpendicularly loaded structural elements is stated in the paper.
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Proceedings of the SHATIS 2022 – 6th International conference on structural health assessment of timber structures
Kunecký, Jiří ; Hasníková, Hana
Structural health assessment of timber structures associates various procedures in order to evaluate the safety and serviceability of structures. Also, it helps to assure or extend the predicted service life of structures. Service life sustainability can be promoted by the incorporation of monitoring systems or by providing tools and methods that deliver accurate reports about the structural condition. Conservation and assessment of timber structures is based on a multidisciplinary approach. The conference topics cover the wide spectrum, from wood properties, through performance of joints and timber design, to modern monitoring and digital technologies. As the topics include both existing and historical timber structures, the need for reliable non destructive testing methods is part of the approach as well.
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Creep of oak dowel: various loading and environmental conditions
Hasníková, Hana ; Kunecký, Jiří ; Hataj, M.
For research of timber joints, the crucial role in force distribution inside the joint is played by distribution and variability of stiffness of the dowels. Not only the instant stiffness, but the one that we can encounter after some longer period. Also, this value and its statistical distribution is influenced by many other factors, however, humidity and temperature are in timber (oak) dowels of utmost importance. In the work results of a creep experiment made using a special testing rig is presented. It has been found, that biggest changes in creep behavior are in case if very humid conditions are present, and, also, that cycling the temperature in high humidity conditions can produce about 104% of the original instantaneous displacement. The result is not surprising, however, new insights are made thanks to relatively high number of samples and ability to produce some statistics. Another outcome is relation of dowel stiffness in time to the level of applied stress, which is quantified in the article.
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The research of wooden dowel-type connectors
Kunecký, Jiří ; Hasníková, Hana ; Hataj, M. ; Milch, J. ; Tyrová, M. ; Suchomelová, P.
The carpentry joints, some of them secured by wooden connectors, are part of historical timber roof structures. Originally, a wooden dowel rather secured the position of timber elements in a joint than transferring loads (e.g. dovetail joints). But in some joints it can also transfer the forces between the structural members, therefore its behaviour influences the stiffness and load-bearing capacity of the whole structure directly. This type of connectors can be used nowadays as well; while reconstructions, a new timber building construction, or manufacturing individual structural timber elements (e.g. panels). Current technical standards do not prescribe a suitable computing procedure for the joints with wooden connectors. Moreover, a complex failure criteria for various fibre directions are missing. The article introduces an ongoing project, whose ambition is to cover the knowledge gap.
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Wooden joints with wooden connectors viewed from dialectic perspective
Kunecký, Jiří ; Hasníková, Hana ; Kloiber, Michal
The paper deals with a critical evaluation of a technology of conservation of decayed wooden structures, especially using the technology of wooden joints equipped with wooden connectors. This technology is nowadays widespread among the people working in the field pf protection of cultural heritage. The main aim was to address price, safety issues, understanding of the principals and contexts of this type of technology. Rational arguments are used to eradicate the myths present in this area and put the light of ratio to debate on this issue.
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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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Material analyses of plaster samples of the historical building named “Nové Probošství”, Pražský hrad, nám. sv. Jiří č.p. 34.
Drdácký, Miloš ; Slížková, Zuzana ; Frankeová, Dita ; Hasníková, Hana ; Hauková, Petra ; Koudelková, Veronika ; Kozlovcev, Petr ; Ševčík, Radek ; Wolf, Benjamin
The report contains the results of the material analyses of plasters and stone samples taken from the facades and interior plasters of the historical building named “Nové Probošství” (Pražský hrad, nám. sv. Jiří č.p. 34).). The topic of the study was determination of the chemical composition and the microstructure of historical plasters and renders, sandstone petrography, porosity of materials by means of MIP, water absorption of plasters by tubes, the water content and the moisture distribution in masonry wall, the content and the chemical composition of water-soluble salts in plasters and renders. The results of the study serves as the basis for the future design of the building renovation and the restoration of the artistic elements.\n
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