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Mechanical analysis of scarf joint fastened using cylindrical wooden dowel
Tippner, J.; Milch, J.; Kunecký, Jiří; Kloiber, Michal; Brabec, M.; Sebera, V.
2017 - English
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.
Keywords:
all-wooden joints; scarf joint; dowel; spruce; oak; digital image correlation
Available at various institutes of the ASCR
Mechanical analysis of scarf joint fastened using cylindrical wooden dowel
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 ...
Korozní chování žárových zinkových povlaků v půdě
Kreislová, K.; Barták, Z.; Fialová, P.; Majtás, Dušan
2017 - Czech
Příspěvek uvádí některé výsledky korozní zkoušky zinkového povlaku v půdě v ČR ve srovnání s dosud publikovanými údaji. V příspěvku je uveden i příklad koroze žárového zinkového povlaku na specifickém mostním objektu. Paper gives some results of corrosion test of zinc coating in soil in the ČR in comparison with contemporary published data. There is given also case study of hot dip zinc coating´s corrosion on specific bridge object.
Keywords:
zinc coating; soils; corrosion test
Available at various institutes of the ASCR
Korozní chování žárových zinkových povlaků v půdě
Příspěvek uvádí některé výsledky korozní zkoušky zinkového povlaku v půdě v ČR ve srovnání s dosud publikovanými údaji. V příspěvku je uveden i příklad koroze žárového zinkového povlaku na specifickém ...
Iron alloys outdoor corrosion and laboratory simulation - comparison
Majtás, Dušan; Mácová, Petra; Kreislová, Kateřina; Příhoda, J.
2017 - English
Simulation of iron alloy corrosion is widespread used to predict corrosion resistance. The simulation using corrosion chambers or climatic chambers provides reasonable information on corrosion resistance, the corrosion rate however must be compared to real exposition as the corrosion in simulated environment is accelerated compared to real situation. However the composition of corrosion products and its structure is different question. The corrosion products composition is dependent on corrosion process. The phases present are most likely the same, most voluminous hydrated oxides and oxy-hydroxides on the outside where the less voluminous oxides are present in the lower layers. However this macroscopic phase structure may not fully describe the layered structure of corrosion products, thickness of corrosion products or mechanical properties. In the vicinity of crack in corrosion products the structure is more likely to be similar to the structure near the surface.
Keywords:
corrosion; wrought iron; accelerated ageing; corrosion simulation
Available at various institutes of the ASCR
Iron alloys outdoor corrosion and laboratory simulation - comparison
Simulation of iron alloy corrosion is widespread used to predict corrosion resistance. The simulation using corrosion chambers or climatic chambers provides reasonable information on corrosion ...
Evaluation of effective properties of basalt textile reinforced ceramic matrix composites
Valentová, S.; Hrbek, Vladimír; Šejnoha, M.
2017 - English
The present paper is concerned with the analysis of a ceramic matrix composite, more specifically the plain weave textile fabric composite made of basalt fibers embedded into the pyrolyzed polysiloxane matrix. Attention is paid to the determination of effective elastic properties of the yarn via homogenization based on the Mori-Tanaka averaging scheme and the 1st order numerical homogenization method adopting a suitable representative computational model. The latter approach is then employed to simulate the response of the yarn when loaded beyond the elastic limits. The required mechanical properties of individual material phases are directly measured using nanoindentation with in-build scanning probe microscopy. Applicability of the proposed computational methodology is supported by the analysis of a unidirectional fibrous composite, representing the yarn, subjected to a macroscopically uniform strain
Keywords:
basalt fibers; textile composites; homogenization; periodic unit cell; damage
Available at various institutes of the ASCR
Evaluation of effective properties of basalt textile reinforced ceramic matrix composites
The present paper is concerned with the analysis of a ceramic matrix composite, more specifically the plain weave textile fabric composite made of basalt fibers embedded into the pyrolyzed ...
Deformation behaviour of gellan gum based artificial bone structures under simulated physiological conditions
Krčmářová, N.; Šleichrt, J.; Fíla, Tomáš; Koudelka_ml., Petr; Kytýř, Daniel
2017 - English
The paper deals with investigation of deformation behaviour of gellan gum (GG) based\nstructures prepared for regenerative medicine purposes. Investigated material was synthesized as porous spongy-like scaffold reinforced by bioactive glass (BAG) nano-particles in different concentrations. Deformation behavior was obtained employing custom designed experimental setup. This device equipped with bioreactor chamber allows to test the delivered samples under simulated physiological conditions with controlled flow and temperature. Cylindrical samples were subjected to uniaxial quasi-static loading in tension and compression. Material properties of plain scaffold buffered by 50 wt% and 70 wt% BAG were derived from a set of tensile and compression tests. The results are represented in form of stress-strain curves calculated from the acquired force and displacement data.
Keywords:
gellan gum scaffold; reinforcement; uni-axial loading; simulated physiological conditions
Available at various institutes of the ASCR
Deformation behaviour of gellan gum based artificial bone structures under simulated physiological conditions
The paper deals with investigation of deformation behaviour of gellan gum (GG) based\nstructures prepared for regenerative medicine purposes. Investigated material was synthesized as porous ...
Non-holonomic planar and spatial model of a ball-type tuned mass damping device
Náprstek, Jiří; Fischer, Cyril
2017 - English
The area of tuned mass dampers is a wide field of inspiration for theoretical studies in non-linear dynamics and dynamic stability. The studies attempt to estimate behaviour of diverse damping devices and their reliability. The current paper deals with the response of a heavy ball rolling inside a spherical cavity under horizontal kinematic excitation. The non-linear system consists of six degrees of freedom with three non-holonomic constraints. The contact between the ball and the cavity surface is supposed to be perfect without any sliding. The mathematical model using the Appell-Gibbs function of acceleration energy is developed and discussed. Comparison with previous planar (SDOF) model which is based on the Lagrangian procedure is given. The system has an auto-parametric character and therefore semi-trivial solutions and their dynamic stability can be analysed. The most important post-critical regimes are outlined and qualitatively evaluated in resonance domain. Numerical experiments were performed when excitation frequency is slowly swept up and down to identify different modes of response. Some applications in civil engineering as a tuned mass damper, which can be used on slender structures, are mentioned. The proposed device is compared with a conventional pendulum damper. Strengths and weaknesses of both absorbers types are discussed.
Keywords:
tuned mass damper; moving ball; Appell-Gibbs formulation
Available at various institutes of the ASCR
Non-holonomic planar and spatial model of a ball-type tuned mass damping device
The area of tuned mass dampers is a wide field of inspiration for theoretical studies in non-linear dynamics and dynamic stability. The studies attempt to estimate behaviour of diverse damping devices ...
Wind-tunnel simulation of thermally unstable atmospheric flow in complex terrain
Pospíšil, Stanislav; Kuznetsov, Sergeii; Kozmar, H.; Michalcová, V.
2017 - English
The paper presents the characteristics of thermal effects in wind-tunnel simulations of the atmospheric boundary layer (ABL) flow developing above complex terrain. The differences and instable stratification effects between the windward and leeward sides of a hill model were investigated for different wind characteristics. Particularly, the buoyancy effects on the structure of the ABL simulation in a wide range of stability conditions expressed by Richardson number are studied.
Keywords:
instable stratification; wind tunnel; Richardson number
Available at various institutes of the ASCR
Wind-tunnel simulation of thermally unstable atmospheric flow in complex terrain
The paper presents the characteristics of thermal effects in wind-tunnel simulations of the atmospheric boundary layer (ABL) flow developing above complex terrain. The differences and instable ...
Remarks on inverse of matrix polynomials
Fischer, Cyril; Náprstek, Jiří
2017 - English
Analysis of a non-classically damped engineering structure, which is subjected to an external excitation, leads to the solution of a system of second order ordinary differential equations. Although there exists a large variety of powerful numerical methods to accomplish this task, in some cases it is convenient to formulate the explicit inversion of the respective quadratic fundamental system. The presented contribution uses and extends concepts in matrix polynomial theory and proposes an implementation of the inversion problem.
Keywords:
matrix polynomial; polynomial eigenvalues; structural vibration
Available at various institutes of the ASCR
Remarks on inverse of matrix polynomials
Analysis of a non-classically damped engineering structure, which is subjected to an external excitation, leads to the solution of a system of second order ordinary differential equations. Although ...
Formace polymorfů uhličitanu vápenatého během mísení koncentrovaných roztoků solí
Ševčík, Radek; Mácová, Petra; Viani, Alberto
2017 - Czech
Příspěvek se zaobírá předběžnými výsledky studia gelové fáze vznikající během mísení koncentrovaných roztoků solí během syntézy polymorfů uhličitanu vápenatého. Během reakce bylo odebráno několik vzorků, které byly následně zkoumány instrumentálními technikami jako např. skenovací elektronový mikroskop. This contribution is demonstrated the preliminary results of the study of the gel phase forming during the synthesis of calcium carbonate's polymorphs. Several samples were collected during the reaction and they were subsequently investigated with instrumental techniques e.g. scanning electron microscopy.
Keywords:
CaCO3; polymorphs; synthesis; vaterite; ACC
Available at various institutes of the ASCR
Formace polymorfů uhličitanu vápenatého během mísení koncentrovaných roztoků solí
Příspěvek se zaobírá předběžnými výsledky studia gelové fáze vznikající během mísení koncentrovaných roztoků solí během syntézy polymorfů uhličitanu vápenatého. Během reakce bylo odebráno několik ...
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.
2017 - English
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).
Keywords:
creep; oak; pegs; dowels; tension
Available at various institutes of the ASCR
Creep behavior of oak pegs under tension in dry and wet conditions
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 ...
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