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Archiv článků od 16.1.2017 do 5.6.2017

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tesařské spoje © martinfredy - Fotolia.com
5.6.2017
Ing. Martin Hataj, doc. Ing. Petr Kuklík, CSc.

A growing environmental awareness and desire for sustainable solutions and healthy living conditions, especially in Europe, lead to an increasing demand for timber structures. High speed, excellent cut quality and accuracy of CNC processing allows an effective produce of timber structures by traditional carpentry procedures. This article responds to current problem of load bearing capacity calculations of traditional carpentry joints. This way of structural joints has not sufficient support in current standards and therefore design relies on simple empirical relationships based on experience. This paper presents the experimental and calculation methods for investigation of static behaviour and load bearing capacity of carpentry joints.

29.5.2017
doc. Ing. Jaroslav Solař, Ph.D., VŠB TU Ostrava

The contribution dealst with the problematics of statical defects, or more precisely with the formation of cracks in the brickwork caused by the effect of technical seismicity. It further deals with the construction principles which can be used when designing reconstruction of buildings which are located within the reach of the effect of technical seimicity. The problematics of historical buildings and conservation areas is also mentioned.

15.5.2017
Ing. Martin Hataj, doc. Ing. Petr Kuklík, CSc.

Computing models for structural behaviour and determination of traditional timber butt joints using analytical relations are presented in this paper. A component method is a base of the computing technique introduced herein. This method is usually used for steel joints 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 in a close proximity of 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 element is stated in the paper.

sklad dřeva © industrieblick - Fotolia.com
8.5.2017
Ing. Martin Keppert, Ph.D., Univerzitní centrum energeticky efektivních budov (UCEEB) při ČVUT v Praze

The papers aims to illustrate possibility to characterize pore system of wood and to quantify its pore size distribution by mercury intrusion porosimetry as simple and fast experimental method.

1.5.2017
Ing. Tomáš Melichar, Ph.D., doc. Ing. Jiří Bydžovský, CSc.

The article presents research into the effect of carbon nanotubes in the blended polymer-silicate matrix containing raw materials from alternative sources. The intention was testing of several variations of mixture composition at the laboratory and also extreme temperature ambient. Assessing the suitability of the matrix composition was carried out by using both basic physico-mechanical parameters and then microstructural analysis methods (on selected samples).

17.4.2017
prof. Ing. Leonard Hobst, CSc., prof. Ing. Jiří Vala, CSc.

Utilization of fibre concrete in building structures, supported by technical standards in preparation, stimulates the development of methods for nondestructive analysis of its structure, crucial for mechanical properties, as fracture resistance under tensile loads. The paper presents an overview of available methods, based i) on image processing and ii) on measurements of electromagnetic quantities.

10.4.2017
Ing. Eva Šopíková, Ph.D., Ing. Petr Vymlátil, Ph.D., prof. Ing. František Wald, CSc., Ing. Anna Kuklíková, Ph.D.

This report presents a new method for designing composite timber steel-fibre-reinforced concrete slabs with unprotected secondary timber beams subject to fire, taking tensile membrane action into account. The FE-model consists of material tests, push-out shear tests and beam tests, which had formed a preliminary study. The FE-model represents the behaviour of the floor slab tested in experiment, together with a collapse prediction for the slab. The FE-model with characteristic material properties includes a safety concept based on the Eurocode standards, and is applied to define the fire resistance of various types of timber steel fibre-reinforced concrete flooring.

3.4.2017
Ing. Jindřich Sobotka, Ph.D., doc. Ing. Karel Šuhajda, Ph.D., Mgr. Zdeněk Jiroušek

This paper discusses the practical use of microwave technology in construction practice. Opinions on the use of EMW devices are not only among the general public quite different. From boundless praise, to the uncritical condemnation. The reason for this situation is the lack of awareness of experts and the public about what is and what is not possible to expect from this technology.The article conclusions which we reached on the basis of experiments conducted at the Faculty of Civil Engineering Brno and subsequently verified measurements in field practice. The aim is to provide basic information about how to use microwave technology. Their benefits but also the risks that this technology brings along.

27.3.2017
prof. Ing. Leonard Hobst, CSc., prof. Ing. Jiří Vala, CSc.

Long-time study of fibre-reinforced concrete, i.e. a composite material with a cementitious matrix, whose structure is hardened by usually randomly distributed fibres (steel ones in the most frequent case), demonstrates good mechanical and other technical properties, which makes possible its utilization in bearing structures. This stimulates the development of methods, non-destructive or low-invasive if possible, for the analysis of its structure, which determines crucial mechanical properties, e.g. fracture resistance under tensile loads. This article, coming from research activities of the Faculty of Civil Engineering at Brno University o Technology, brings an overview of available methods, namely direct methods coming from image processing and indirect ones utilizing measurements of electromagnetic quantities.

20.3.2017
Ing. Hynek Kundera, Ing. Andrea Nasswettrová MBA, Ph.D., Ing. Olga Grossová, Ing. Pavel Šmíra MBA, Ph.D.

The article deals with hot-air treatment of a historically valuable Rožnov town office, built in 1770, which was transported to the Wallachian Open Air Museum in Rožnov pod Radhoštěm in 1924 as the first building of the currently extensive premises of this national cultural heritage. The method of wooden structure hot-air treatment was used for the first time in the territory of the Czech Republic in 2010. It has been used in western European countries (especially Denmark and Germany) approximately since 1930. This comprehensive method is governed by the German standard DIN 68 800 – Part 4 [1] and it is especially used for historically valuable buildings where emphasis is put on the preservation of the original wooden structure attacked by wood-destroying insects, usually of the long-horn beetle family (Cerambycidae) oranobium beetle family (Anobiidae). The goal of the article is to explain the hot-air treatment method to professional public using an example of one of implementations.

8.3.2017
Ing. Zdeněk Lyčka

The article explains the differences between the invention patents and utility model from the perspective of Czech legislation. Also highlights the confusion individual categories and purposeful fraud by producers and sellers of equipment.

6.3.2017
Ing. Šárka Nenadálová, Ing. Lukáš Balík, Ph.D., Ing. Milan Rydval, Ing. Tomáš Bittner

Water vapour permeability is one of significant material properties. The value of water vapour resistance factor is necessary to know to be able to rehabilitate structures, mainly after floods. One thing is essential – to know what are the values of water vapour resistance factor of the used material to know how long the structure will take to be dried and users can come back to live there.

27.2.2017
Mgr. Martin Vyšvařil, Ph.D., RNDr. Markéta Rovnaníková, Ph.D.

Sulfate attack is one of the major threats for durability of concrete in sewage collection systems where concrete sewer pipes are exposed to sulfates from waste water as well as from biogenic activity of bacteria. Damage due to sulfate interaction can result in the cracking and softening with loss of strength of concrete and it may lead to the concrete desintegration. Gypsum is the primary product of sulfate attack on concrete, after which ettringite is subsequently formed. Ettringite and gypsum are considerably larger in volume than the initial compounds, which leads to increased pressure within the concrete structure. This paper is focused on the sulfate attack on fine-grained concrete where the effect of 12 months contact of 0.5% sulfuric acid, simulating biogenic sulfuric acid corrosion, 5% sodium sulfate solution and solution simulating sewage water on various types of concrete has been investigated. The concrete specimens were characterized after exposition to the corroding media by their mechanical parameters, changes in pH and content of sulfates. It was found that after one-year exposure to sulfuric acid solution, the compressive strengths of all types of concrete significantly decreased. Sodium sulfate solution and the artificial waste water did not represent the significant corrosion environments for the concretes in terms of their strength reduction, increasing of sulfate ions content and the reduction in the pH of their aqueous leaches. The fine-grained concretes containing metakaolin and ground limestone showed the highest coefficient of corrosion resistance for the applied corrosive solutions.

20.2.2017
Ing. Josef Fládr, Ing. Petr Bílý, Ph.D.

The paper presents the first findings of comprehensive research program focused on the investigation of resistance of UHPC to deicing chemical agents and freezethaw cycles. Several series of tests were conducted to compare the behavior of UHPC and reference C40/50 class fibre-reinforced concrete.

30.1.2017
Ing. Eva Šopíková, Ph.D., Ing. Anna Kuklíková, Ph.D., Ing. Petr Vymlátil, Ph.D., prof. Ing. František Wald, CSc.

The subject of this paper is a comparison of two experiments of timber-fibre concrete floors in fire, which consist of steel fibre reinforced concrete boards and glue-laminated timber beams. Main aim of this project is to assess the using of steel fibre reinforced concrete board, which work together with glue-laminated timber beams to increase fire resistance and investigate its behaviour in loaded construction.

23.1.2017
Ing. Lubomír Šabatka, CSc., prof. Ing. František Wald, CSc., Ing. Jaromír Kabeláč, Ing. Drahoslav Kolaja

Steel frame structures are commonly analyzed three dimensionally by 1D elements. Connection of elements to joints is assumed to be perfectly rigid, nominally pinned or semi-rigid. The new CBFEM method allows to properly model the connection. The bending/deformation stiffness, resistance and deformation capacity of connections of individual members is evaluated. CBFEM model is loaded with appropriate internal forces obtained by global analysis. The article explains loading of a detailed 3D model of a joint. It also addresses situation where actual structural design of the joint does not match theoretical expectations of the global analysis.

16.1.2017
Ing. Milan Rydval, Ing. Tomáš Bittner, Ing. David Čítek, Ing. Šárka Nenadálová

The paper is focused on comparison of different types of compressive tests of samples exposed to high temperature. The tests could be divided into two basic types. The first type of the test is an ambient temperature testing to obtain residual compressive strengths and the second type is a hot state testing to obtain mechanical parameters of concrete exposed to high temperature.

16.1.2017
Ing. Jiří Rathouský, CSc., Centrum pro inovace v oboru nanomaterálů a nanotechnologií, Ústav fyzikální chemie Jaroslava Heyrovského, v.v.i., AV ČR

The removal of unwanted material from the surface of historical artefacts is one of the most important and also the most delicate operations in the restoration of cultural heritage. In the Center for innovations in the field of nanomaterials and nanotechnologies a novel design concept of the cleaning microemulsions was developed based on a combination of the two functions, implemented by two components, namely a micellar solution or microemulsion of nonionic surfactants with the addition of co-surfactants and the specific solvents, which are selected according to the respective substances to be removed. The patented cleaning compositions can very effectively and selectively remove coatings of many substances important for the restoration practice, such as waxes, resins (e.g, Damara), paraffins, oils, water acrylate dispersions, hydrophobization coatings (both monomeric and polymeric) etc. Besides the efficient cleaning, the developed procedures have wider applications, such as in a new method of the hydrophobization of sandstone and limestone materials with a thin hydrophilic surface layer, which has been certified by the Ministry of Culture of the Czech Republic.


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