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Archiv článků od 12.7.2021 do 27.12.2021

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27.12.2021
doc. Ing. Jana Marková, CSc., ČVUT Praha, Kloknerův ústav

The new Eurocodes for basis of design and actions are almost completed and the final phases of their minor modifications are underway within the working groups of technical subcommittees SC1 and SC10. Their national availability for translations and preparation of national annexes is planned between 2023 and 2025, their implementation and withdrawal of the current Eurocodes in 2028. For the operational implementation of the new generation of Eurocodes, it will soon be necessary to prepare new national annexes and optimally set the values of nationally determined parameters, including calibrations of partial factors for loads and material properties, to ensure reliability, safety and economy of our buildings. It is expected to use the potential of our experts, as well as the considerable financial resources will be needed for the national implementation of the new Eurocodes and the publication of new manuals with practical applications.

14.12.2021
doc. Ing. Jaroslav Sandanus, PhD., doc. Ing. Kristián Sógel, PhD.

This paper deals with the diagnostics of a timber load-bearing structure before planned renovation of covering structures. The roof and facade cladding can also change the load conditions, therefore, the inspection static design in this case is necessary. The planned object renovation is an opportunity for elaboration of diagnostic inspection of the supporting structure.

3D tisk
6.12.2021
Ing. arch. Roman Bolcek, Bc. Dominik Lehnert, Ing. arch. Viktor Schwab, Ing. Zdeněk Vejpustek, Ph.D., Ing. et Ing. Petr Hlavsa, Ph.D.

The paper discusses additive manufacturing in the building industry in terms of definition of terminology, application technology, machinery and materials to be used. It gives examples of executed buildings and discusses the possibilities of using natural materials for 3D printing of buildings. Current research and future prospects in the field of additive manufacturing are presented. The paper was created within the framework of specific research at the Faculty of Architecture of Brno University of Technology, where the possibilities of 3D printing from natural materials will be further analyzed.

Stavba mostu z předpjatého betonu © Stock Adobe Miroslav Doubrava
28.11.2021
Ing. Jakub Kralovanec, doc. Ing. Martin Moravčík, PhD.

There are situations when it is necessary to determine the state of prestressing at a specific time on existing structures. In these cases, it is possible to use indirect methods for determining the state of prestressing. These methods consist of the observation of selected quantities on the investigated structure. Subsequently, based on obtained results it is possible to analytically calculate the actual state of prestressing. The observed quantities include e.g., strain, deformations, crack width etc. This paper presents an overview of possible indirect methods for determining the prestressing in the structure.

1.11.2021
prof. Ing. Pavel Kuklík, CSc., ČVUT v Praze, Fakulta stavební, katedra mechaniky

The paper deals with the determination of strength characteristics of masonry composite. The MQI strategy, published by the staff of the University of Perugia, is presented. The calculation is based on a certain value analysis of several parameters, based on which the MQI masonry index is calculated. The index is then calibrated so that the strength characteristics of the masonry according to the new Italian standards can be determined from its value.

25.10.2021
Ing. Richard Fürst, Ing. Marek Pokorný, Ph.D., Ing. Tomáš Vlach, Ing. arch. at Bc. Petr Hejtmánek, Ph.D., doc. Ing. Vladimír Mózer, PhD.

Modern composite materials are increasingly used in construction. One example is textile reinforced concrete (TRC), consisting of high-quality concrete and non-metallic reinforcing materials, most often in technical textiles. The current use of TRC is mainly in non-loadbearing structures such as facade panels and design elements. However, due to the excellent mechanical properties of TRC, it is possible to design subtle structures with high load-bearing capacity. Therefore, this material has a high potential in load-bearing structures. Consequently, it is necessary to comprehensively assess these materials in terms of load-bearing capacity at normal and elevated temperatures. For this reason, within the Faculty of Civil Engineering CTU in Prague and UCEEB CTU in Prague, research teams deal with the development and material research of TRC for use in load-bearing structures, including evaluation of its possible application in construction.

Počítačové modelování kmitání membránové konstrukce
14.10.2021
Ing. Lenka Štulerová, Ing. Lukáš Kapolka, prof. Ing. Stanislav Kmeť, CSc.

The aim of this paper is the modal analysis of a thin technical textile in shape of hyperbolic paraboloid. It is the geometrically nonlinear membrane structure, which can function only in tension. In this case, the structure was subjected to the natural vibration as a part of the overall dynamic analysis. All of this results in natural frequencies and mode shapes and deflections. Acquired results describe the dynamic behaviour of nonlinear system without affect of the external load. This part could represent a first step in the dynamic analysis and exactly the forced vibration as nonlinear time history analysis will have to be performed in a future to complete it.

12.10.2021
Ing. Jan Břečka, Ing. Kristýna Hrabovská

The aim of this study is to find the dependence between the span and cross section area and other choose parameters of the timber-concrete composite beams. For analysis, we used coniferous wood C24 category and concrete C25/30 and C30/37 class with 50 mm thickness. We set the SFS Intec coupling elements. For calculation was used linear elasticity design method. Pliability of composite was take into account per γ-coefficient (γ-method).

27.9.2021
Ing. Michal Janků, Ph.D., Ing. Jiří Grošek, Ph.D.

Good, well-functioning infrastructure signifies a well-run national economy and the overall state of development of the whole society. Buildings, bridges, roads, and other structures need to be regularly maintained if they are to last. In general, if a defect is detected early, the cost of its remediation is typically much lower than if it the structure is allowed to degrade for months or years. Early defect detection often means detecting one before it is visible to the naked eye. A key means of locating hidden defects are non-destructive testing methods. The article describes selected non-destructive methods that can be used in the diagnosis of bridge structures.

25.9.2021
Ing. Ondřej Šimek, doc. Ing. Miloš Zich, Ph.D.

The article presents the results of experiments of reinforced concrete walls with an opening, which have been tested for load carrying capacity in the diagonal direction. These are the walls that represent shear walls in multistorey precast concrete frame structures. The influence of various types of reinforcement on their load carrying capacity and deformation is studied on the designed walls. The data obtained by the experiment is then validated by computational models that represent the behavior of the samples during the experiment. The results of the models are compared between each other and pros and cons are assessed.

Železobetonová konstrukce - ilustrační obrázek
13.9.2021
doc. Ing. Karel Vojtasík, CSc., doc. RNDr. Eva Hrubešová, Ph.D., Ing. Marek Mohyla, RNDr. Jana Staňková Ph.D.

The paper presents the outputs of a computational parametric study investigating the influence of both reinforcement ratio and scheme of a cross-section reinforcement on a design value of the elastic module for the homogenized cross-section and the values of the stress redistribution coefficients. The design value of the elastic module represents the steel-concrete cross section in the calculations. The stress redistribution coefficients converts the state stress in the homogenized cross-section for the state stress in steel and concrete individually. The design value of the homogenized cross-section elastic module and the stress redistribution coefficients are determined from the theory of the cooperating rings and are computed by program HOMO. The result of a study is a set of the stress redistribution coefficients and a dependency of stress redistribution coefficients on the reinforcement ratio of a steel-concrete section.

30.8.2021
doc. Ing. Karel Vojtasík, CSc., doc. RNDr. Eva Hrubešová, Ph.D., Ing. Lukáš Ďuriš, Ph.D.

The paper exposes knowledge referring a correspondence of stress states in the cross-section of steel concrete lining. The two different theories size the stress states. The first a theory of cooperating rings is pursued at department of geotechnics. The second referential is a reinforced concrete theory in use at building construction habitually. The correspondence targets the evaluation of suitability and the working condition of a cooperating rings theory to state the stress in the cross-section of steel concrete lining. An investigation was work out on a steel concrete section having been endorsing by lattice girder.

3D tisk budov
23.8.2021
Ing. Josef Kamenický, Ing. Marek Štádler

3D printing technology has contribution in building automatization. Today, printed buildings for everyday usage already exist. 3D printers movements are controlled by G-code. These buildings are described geometrically and then it's transformed in G-code by postprocessor. That one for building printing must respect the properties of printing mixtures. This work designs new postprocessor for building printing. It must include mathematical model of material according to which G-code for specific building geometry will be generated. In the work are proposed experiments to find out parameters for mathematical material model.

15.8.2021
Ing. Pavel Koudela, Ing. Juraj Chalmovský, Ph.D., doc. Ing. Lumír Míča, Ph.D.

Fibre reinforcing of the soils is one of the methods used for improving the properties of the soils. The many research papers were interested in the fibre reinforcing however, used fibres were straight with smooth surface usually. These properties may not ensure sufficient interaction between soil aggregates and fibres. This disadvantage could eliminate by modification of shape or surface of each fibre and achieve a higher strength of the soil-fibre composite. In this paper is present the soil reinforcing by fibres manufactured by 3D printer. The fibres with the various shapes were made and tested. In the case of the modified fibres, the higher peak strength of the composite occurred.

11.8.2021
Ing. Martin Nguyen, doc. Ing. Radomír Sokolář, Ph.D.

This article examines the process for the synthesis of forsterite–spinel refractory ceramics from different raw materials. Raw materials were milled, mixed in different ratios and sintered at 1500 °C for 2 h. Sintered samples were characterized by XRD and SEM. Porosity, water absorption, bulk density, refractoriness, refractoriness under load and thermal shock resistance were also investigated. The impact of different raw material mixtures was investigated in accordance with the resulting properties and microstructure of all fired samples. Presence of spinel in fired samples led to improved microstructural and mechanical properties and thermal shock resistance. In particular, mixtures with 10–20 % of spinel had the most promising results.

5.8.2021
Ing. Simona Šarvaicová, Slovenská technická univerzita v Bratislave, Stavebná fakulta, Katedra betónových konštrukcií a mostov

This paper deals with experimental verification of punching shear resistance of a slab fragment. An experimental specimen with thickness of 0.2 m is supported by a rectangular column with cross-sectional dimensions of 0.15 × 0.9 m, as a result of which the shear stress is concentrated in the area of the support corners. As a result of this phenomenon, it is necessary to reduce the length of the control perimeter. Based on the results obtained from the experimental test and from the nonlinear analysis in the Atena program, the real necessity to reduce the length of the control perimeter was analyzed using the Eurocode 2 shear resistance evaluation formula. Subsequently, the reliability of selected design models was verified.

29.7.2021
Ing. Ivana Kumpová, Ústav stavební mechaniky, Fakulta stavební, Vysoké učení technické v Brně

The method of X-ray micro-tomography is increasingly used in the research of material characteristics and fracture behavior of building materials. It brings promising results in the field of three-dimensional observation and quantification of microstructure elements, including fracture objects. However, with the standard approach to the tomographic data acquisition, the achievable resolution is severely limited by the size of the examined object resulting in a reduction or even complete loss of useful information regarding, for example, the shape and size of the fracture process zone. For this reason, the possibilities of tomographic targetting of the region of interest with a higher achievable resolution than the usual limit of the tomographic systems have been tested in this work.

19.7.2021
Ing. Petr Figala, VUT FAST Brno, Ústav technologie stavebních hmot a dílců

This work deals with research and development of a new grouting mortar with increased chemical resistance based on portland cement. The aim of this work is to verify new mixtures with specific admixtures. Resistance to attack by external sulphates was monitored, while the test specimens were placed in a sulphate solution of 29.8 g / l (44 g / l Na2SO4) according to DIN 19753. The results of the work show that the addition of the optimal amount of crystalline waterproofing admixture can achieve a significant increase in resistance to sulfate corrosion. Based on the obtained results, new mixtures will be proposed, optimized by the addition of suitable secondary raw materials.

Membránová konstrukce stabilizující ocelový oblouk
19.7.2021
prof. Ing. Josef Macháček, DrSc., Ing. Ondřej Svoboda, Ph.D.

The article is a follow-up to the Part 1: Experiments and analysis [1], in which a numerical model dealing with membrane structures supported by steel arches in software SOFiSTiK using 3D GNIA and 3D GNA is introduced and validated. This part investigates parametrically stability and buckling of arches of a barrel type membrane structure using linear buckling analysis (3D LBA). The in-plane and out of plane buckling factors of the arches for a vast spectrum of practical geometrical parameters of the structure, membrane pretension and support conditions of the arches and membrane frontiers are presented and confronted with the ones belonging to the arches alone.

Detail ocelovo-membránové konstrukce
12.7.2021
prof. Ing. Josef Macháček, DrSc., Ing. Ondřej Svoboda, Ph.D.

The article describes and analyses testing of a shelter model with a textile membrane supported by a steel tube arch. The goal of the investigation is the spatial behaviour of the arch regarding its design. The difference in behaviour of the build-in arch alone and the one in the membrane structure is investigated. The entry data, prestressing and loading procedures are shown including test results. SOFiSTiK software was used for the elastic geometrically nonlinear analysis with imperfections (GNIA) respecting the orthotropic behaviour of the membrane (Précontraint FERRARI®). The successful validation of numerical results by tests warrants the extensive parametrical studies dealing with stability of arches in barrel type membrane structures in the second Part of the article.


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