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Archiv článků od 7.3.2022 do 29.8.2022

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tmel
29.8.2022
Ing. Adam Boháček, Ing. Michal Brandtner

The article deals with sealing of cement-based materials and tensile properties of the sealed joint. Aquapanel cement board was chosen as the base material, which was treated with a primer. Then two sealants were applied, one representative of acrylic and one of polyurethane sealants. After curing, the resulting test specimens were tested according to the valid European standard ČSN EN ISO 8340, which defines the parameters of the test specimen and subsequent test procedures. The evaluation of the test, which took place visually and with a caliper measurement, showed that only polyurethane sealant could be recommended for sealing Aquapanel. This putty, unlike acrylic putty, did not show any defects after the test, so it can be stated as suitable for sealing Aquapanel cement board.

15.8.2022
prof. Ing. Josef Macháček, DrSc., ČVUT v Praze, Fakulta stavební

Part 2 covers buckling lengths of three-hinged arches both with the crown hinge of a fork type (in the arch plane) and a full type (both in and out of the arch plane). The article follows the Part 1 [1] which deals with two-hinged and built-in arches. All studies present three uniform loading patterns (vertical along the arch length, vertical to the arch plan or radial to the arch axis). Buckling lengths of the equivalent straight (Euler’s) column with the constant axial force corresponding to maximal axial arch force in the arch bases are presented in the form of graphs for CHS (circular hollow sections), various open rolled IPE and HEB sections.

8.8.2022
prof. Ing. Josef Macháček, DrSc., ČVUT v Praze, Fakulta stavební

Results of extensive study concerning buckling lengths of circular steel arches are presented. The study in Part 1 covers two-hinged and built-in arches, in Part 2 three-hinged arches with the crown hinge of a fork type (in the arch plane only) and a full type (both in and out of the arch plane). All studies present three uniform loading patterns (vertical along the arch length, vertical to the arch plan or radial to the arch axis). Buckling lengths of the equivalent straight (Euler’s) column with the constant axial force corresponding to maximal axial arch force in the arch bases are presented in the form of graphs for CHS (circular hollow sections) and various open rolled IPE and HEB cross-sections. The study is a follow-up of the author’s article Stability of Steel Circular Arches [1], embodying the preliminary stability analysis of two-hinged arches.

3.8.2022
Ing. Ľudmila Kormošová, Stavebná fakulta STU v Bratislave

The article deals with experimental investigation of the influence of openings orientation on the punching resistance of flat slabs. Within the experiments, two isolated fragments of flat slabs were tested. Both specimens were weakened by two symmetrically placed openings with dimensions of 240 mm × 150 mm adjusted to the shorter side of the elongated column with cross-section of 950 mm × 150 mm. The specimens differed from each other by the orientation of the openings in relation to the support. In addition to the comparison of deformations, the actual control perimeter lengths of the tested specimens were calculated based on the results. Compared to the theoretical lengths of the control perimeters according to EC2, the reduction of the control perimeter appears to be conservative.

1.8.2022
Ing. Jakub Niedoba, doc. Ing. Tomáš Vymazal, Ph.D.

This paper discusses the feasibility of long-term monitoring using modern sensors and systems. New technologies are making long-term monitoring more accurate simpler and more successful. Currently there are many buildings that are monitored for a long time with its subsequent condition assessment, and thanks to the installed sensors and systems it has been possible to detect hidden and emerging defects and damages. Based on the current condition of the structure, it has been possible to carry out timely repairs or maintenance of the building which ultimately saves economic and time costs for the building, ensures safety and increases the life and durability of the building.

21.7.2022
Ing. Matúš Neusch, STU v Bratislave, Stavebná fakulta, Katedra kovových a drevených konštrukcií

This paper deals with experimental verification of semi-rigid timer connections using modern timber connectors Rothoblaas Alumidi. The experiment consists of the loading of timber bracket of structural wood. There are 4 alternatives of connection prepared. Each alternative has 4 specimens. So far, 4 specimens out of a total of 16 specimens have been verified. The paper describes the preparation of the experimental set-up, the loading procedure, the preliminary findings and the results of the performed experiments. These results are confronted with numerical calculations and assumptions of previous theoretical research. Experiment research continues with the testing of additional specimens.

11.7.2022
Ing. David Brandejs, Ing. Pavel Klika, Ph.D.

In preparing an expert opinion, estimate or valuation of any real estate, account should be taken not only of the type of property and the purpose of the valuation, but also of all factors which more or less affect their value or may affect it, in such a way that the slightest influence is incorporated. as a result of the award. One of these influences is tourism, in terms of the number of tourists who visit this locality. The impact of tourism on the market value of recreational facilities, residential real estate and other commercial purposes has already been partially mapped. However, the impact of tourism on the market value of residential properties has not yet been mapped and there are currently no relevant valuation procedures that can assess this impact. The following text contains an evaluation of one, as yet very little explored, intangible factor that may affect the price of real estate.

4.7.2022
prof. Ing. Peter Turček, PhD., doc. Ing. Monika Súľovská, PhD.

The paper deals with the methods of checking the performed sealing works in its second part. Measurements of the permeability of the grouted environment in the field are evaluated, the findings of the grouting records are analyzed and the cement content in the taken samples of the grouted soil was determined in laboratory conditions. Finally, the recommendations for remediation are summarized.

27.6.2022
prof. Ing. Peter Turček, PhD., doc. Ing. Monika Súľovská, PhD.

The ever-recurring high levels of the river Danube have forced Bratislava to be protected from floods. In the western part of the city, it was necessary to ensure the sealing of the heterogeneous fills located just on the banks of the Danube. The performed sealing works did not take into account the actual properties of the subsoil. The first part of the paper deals with the factual situation at the site and the shortcomings of subsoil injection.

20.6.2022
Ing. Miloš Slivanský, PhD., Ing. Roman Herda

The paper deals with the theoretical shape and stability analysis of a timber grid-shell structure. The peculiarity of the approach to the analysis of this type of construction is manifested in several parts of the design process due to the complicated shape of the roof plane. These specifics can be applied to the initial phase of creating the shape of the structure, which is directly related to the resulting static efficiency of the final design. Other important parts of the structural analysis that deviate from the standard-defined procedures are the determination of the design load by external climatic influences and the stability analysis with the need to apply a geometrically nonlinear calculation with the influence of initial imperfections.

13.6.2022
Ing. et Karla Háva, Ing., VUT v Brně, Ústav soudního inženýrství

Ukraine has a strong influence on prices and availability of some construction materials. Steel products are the most hit by the war. Rising prices of energies and fuels are influencing the prices of construction materials, too. These unfavourable conditions are seen not only by small investors, but also by municipalities when announcing public tenders. The original price that won the public tender usually rises during the project’s preparation phase and subsequent construction phase. The author of this article analyses the construction materials’ price developments during a period of several years. In the article you can find a pricing of a particular public tender by indicative prices of construction materials and work in different periods.

23.5.2022
Ing. Adam Petrík, doc. Ing. Rudolf Ároch, PhD.

Computer simulations require appropriate input data to match the relevant calculated results with those of experiments. The true stress-strain curve suitable for finite element analysis is describing the non-linear behaviour of the steel with a proper relationship from beggining of loading to failure of the test specimen. The pre-peak part of the curve can be easily covered by an analytical method, but the necking part of the curve cannot be described by such a relationship between the normalized and the true stress-strain curves. Simple numerical tensile test of a steel specimen was performed to establish the true stress-strain curve in ANSYS software. Stress and strain from the computer analyses were compared with the results of the experimental tensile test.

17.5.2022
Ing. Maroš Mojto, prof. Ing. Ján Brodjansky, PhD., Ing. Tomáš Klass, PhD.

This paper deals with geometrical tolerances in the conical hollow tubes used in slip joints. Tubes are circular or polygonal cross-sections. The contribution includes standards concerning the tolerances. Based on the standards the imperfections in experimental specimens are evaluated. It is possible to say that it is not simple to state the shape and the allowed value according to standards. It is also possible to conclude that the experimental specimens include non-considerable imperfections.

3.5.2022
Ing. Pavel Klika, Ph.D., Ing. David Brandejs, Ing. Vítězslava Hlavinková, Ph.D., Ing. Monika Doležalová, Ing. Martina Vařechová

In connection with the natural disaster that hit the Břeclav and Hodonín regions in June last year, more than a thousand houses, buildings, halls and other structures were damaged or completely destroyed. Real estate was owned by both natural and legal persons, as well as by cities, municipalities and state institutions. Several state and non-state, for-profit and non-profit organizations came with financial help. To determine the amount of support, subsidy or loan, it was required to document the estimated costs of compensation. The estimated costs were determined on the basis of several methods, taking into account the type and type of real estate, ownership, and the extent of damage. The methods used to determine the estimated costs of compensation are described below.

26.4.2022
Ing. Tomáš Melichar, Ph.D., doc. Ing. Jiří Bydžovský, CSc., Ing. Lenka Mészárosová, Ph.D., Ing. Amos Dufka, Ph.D.

One of the very essential aspects to ensure adequate durability of composite materials that combine cementitious matrix and wood is the stabilization of the wood structure. Stabilization of the wood structure is particularly important in relation to the moisture effect on the wood-cement composite mechanical properties. Stabilization of the wood matrix is generally carried out by means of suitable types of additives. This paper deals with a detailed analysis of the influence of the wood-cement materials composition in relation to the effect of liquid water. Another essential area of the presented research is the analysing the ability of the modified matrix (by different types of industrial wastes) to fix sugars in the structure of the wood mass, with regard to the possible affecting the hydration process of the cement matrix.

17.4.2022
Ing. Ján Mihálik, Ing. Filip Gago, PhD., Ing. Martina Buková

The article is focused on the evaluation of the static load test of piles by various methods. The aim of the evaluation is to obtain design values of the experimental bearing capacity of the piles. The analysis contains evaluated 10 static load tests performed on large-diameter piles of various lengths, which are located in the same engineering geological district and are made as drilled piles with a casing. Each test is evaluated according to STN 73 1002, according to the Brinch Hansen method 80% criterion and according to the Davisson method of ultimate strength.

15.4.2022
Ing. Michal Novotný, Ing. Tomáš Chorazy, Ph.D.

The current way in drainage of roads is the concentration of rainwater in the subsoil of roads, so that rainwater does not drain into the sewer system, but freely infiltrates into the subsoil. The aim of this research is to optimize the structural layers of green parking lots with AS-TTE grassing blocks. During the design of structural layers and new types of materials, will be optimized to allow maximum water infiltration into the subsoil and at the same time keep the requirements for load-bearing capacity of structural layers according to ČSN 72 1006. Laboratory tests will be performed focusing on basic physical and mechanical properties, water permeability and adsorption of oil drips.

Analýza schodišťového stupně z ultravysokohodnotného betonu
1.4.2022
Ing. Dominik Lisztwan, Ing. Petr Daněk, Ph.D.

In this contribution, experimental and numeric analysis of slender stair tread model made of an ultra-high performance concrete, is described. Task of the analysis is to determine the behaviour of the model under acting load. The experimental part is represented by the static load test with the use of a vacuum method. Besides that, nonlinear numerical analysis in the environment of the ATENA Science software, is described. Gained results from both parts of the analysis are compared and unusual behaviour of the model is discussed.

15.3.2022
Ing. Ondřej Nespěšný, Ing. Jan Vystrčil, Ing. Dominik Cakl

Stairs are an integral part of multi-storey buildings and must meet a few ones based mainly on technical standards. One of the basic requirements for buildings is mechanical resistance and stability, which is currently often verified by calculation methods. If the calculation methods are insufficient, the experimental methods of loading the structures described in this publication must be used. The paper summarizes the course of static loading of prefabricated stair assemblies made of composite materials based on cement and reinforcing organic fibers. The applied methods are based on European standards and guidelines for technical technical approval.

© photo 5000 - Fotolia.com
7.3.2022
Ing. et Ing. Karla Háva, VUT FAST Brno, Ústav soudního inženýrství

Producers and suppliers of construction materials are dealing with rising prices of raw materials, semi-finished products and lots of different types of products. Insecurity of input raw material supplies for production is on the rise as well. This is due to the concurrence of many unfavourable circumstances.

Plastics are now being directed primarily to healthcare, mainly for the production of protective aids against virus transmission. A large amount of plastics is used for disposable food containers or packaging of goods, which is now more than ever ordered online. The outage of production capacity of global plastics producers in the USA has the biggest impact on plastics prices. Lack of plastics in the US influences significantly the quantity of plastics available on European markets. The subsequent withdrawal of plastics from China and Europe significantly contributes to logistics complications. Insufficient capacity of transport ships, aircraft and rail transport makes delivery times longer.

Reduction or termination of production of some smelters in Europe, rising emission allowance prices, tariff restrictions and a shortage of metals from Asia are contributing to raise metal prices. It is seen on the London Metal Exchange.

Although the long-term bark beetle calamity is not at its end yet, foresters have succeeded in stopping it in many places in the Czech Republic. Logging of bark beetle timber is decreasing and its price increases. The increase is caused not only by the decrease in logging, but also by export of this timber abroad, particularly to China, which is a phenomenon of the last two years.

Pandemic restrictions have impact on availability of workers for materials production, products logistics, sale and on-site assembly. There was a slowdown in construction output in spring and summer 2020. However, a recovery phase has been seen recently and demand for many materials exceeds supply.


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