Concrete Structures Restoration from the Fire Safety Point of View

2013 ◽  
Vol 688 ◽  
pp. 113-119 ◽  
Author(s):  
Isabela Bradáčová ◽  
Petr Kučera
Keyword(s):  
Critical Temperature ◽  
Temperature Distribution ◽  
Concrete Structures ◽  
Concrete Cover ◽  
Point Of View ◽  
Engineering Practice ◽  
Cover Layer ◽  
Subsequent Determination ◽  
Bearing Structure

The need of concrete structures restoration in order to ensure their fire resistance can, in engineering practice, occur for reasons of damage to the structure by fire (spalling of concrete cover layer) or by the failure to cover the load-bearing structure during construction. The paper is devoted to the evaluation of the structure cover of the evaluated structure, the determination of temperature distribution in the structure with consideration to the choice of probable fire scenario, subsequent determination of critical temperature of the structure and the optimization of possible methods of the restoration of damaged or wrongly made constructions.

scholarly journals Overview of the modified magnetoelastic method applicability

ACTA IMEKO ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 167
Author(s):  
Tomáš Klier ◽  
Tomáš Mícka ◽  
Michal Polák ◽  
Milan Hedbávný
Keyword(s):  
Prestressed Concrete ◽  
Concrete Structures ◽  
Engineering Practice ◽  
Structural Elements ◽  
Engineering Structures ◽  
Advantages And Disadvantages ◽  
Axial Forces ◽  
Technical Practice ◽  
Tensile Forces

<p class="Abstract">A requirement of axial force determination in important structural elements of a building or engineering structure during its construction or operational state is very frequent in technical practice. In civil engineering practice, five experimental techniques are usually used for evaluation of axial tensile forces in these elements. Each of them has its advantages and disadvantages. One of these methods is the magnetoelastic method, that can be used, for example, on engineering structures for experimental determination of the axial forces in prestressed structural elements made of ferromagnetic materials, e.g., prestressed bars, wires and strands. The article presents general principles of the magnetoelastic method, the magnetoelastic sensor layout and actual information and knowledge about practical application of the new approach based on the magnetoelastic principle on prestressed concrete structures. Subsequently, recent results of the experimental verification and the in-situ application of the method are described in the text. The described experimental approach is usable not only for newly built structures but in particular for existing ones. Furthermore, this approach is the only one effectively usable experimental method for determination of the prestressed force on existing prestressed concrete structures in many cases in the technical practice.</p>

scholarly journals Stylistic Peculiarities of the Political Internet-Discourse (Based on Comments to Theresa May’s Posts in Twitter)

2020 ◽  
Vol 2020 (1) ◽  
pp. 77-84
Author(s):  
Boris G. Vulfovich
Keyword(s):  
Speech Act ◽  
Emotional Reaction ◽  
Point Of View ◽  
Stylistic Analysis ◽  
The Political ◽  
The Internet ◽  
Subsequent Determination ◽  
The Given ◽  
High Possibility

Modern political discourse has obtained a new level, i.e. bilateral due to the Internet. This feature of this social network lets a user make a comment to any post written on the page and, what is more, there is a high possibility that a person addressed will read it and answer it. As a comment is considered to be an individual’s speech act it can be rendered from stylistics’ point of view. Implying stylistics into speech can be explained by an attempt to cause a certain emotional reaction of a person. The given article deals with the stylistic analysis of such comments to Theresa May’s posts in “Twitter” and subsequent determination of the emotive state of the readers.

Improvement Of Curvilinear Diagrams Of Concrete Deformation

2019 ◽  
pp. 99-104
Keyword(s):  
Reinforced Concrete ◽  
Peak Load ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Deformation Model ◽  
Reinforced Concrete Structures ◽  
Significant Difference ◽  
Deformation Diagrams

Problems when calculating reinforced concrete structures based on the concrete deformation under compression diagram, which is presented both in Russian and foreign regulatory documents on the design of concrete and reinforced concrete structures are considered. The correctness of their compliance for all classes of concrete remains very approximate, especially a significant difference occurs when using Euronorm due to the different shape and sizes of the samples. At present, there are no methodical recommendations for determining the ultimate relative deformations of concrete under axial compression and the construction of curvilinear deformation diagrams, which leads to limited experimental data and, as a result, does not make it possible to enter more detailed ultimate strain values into domestic standards. The results of experimental studies to determine the ultimate relative deformations of concrete under compression for different classes of concrete, which allowed to make analytical dependences for the evaluation of the ultimate relative deformations and description of curvilinear deformation diagrams, are presented. The article discusses various options for using the deformation model to assess the stress-strain state of the structure, it is concluded that it is necessary to use not only the finite values of the ultimate deformations, but also their intermediate values. This requires reliable diagrams "s–e” for all classes of concrete. The difficulties of measuring deformations in concrete subjected to peak load, corresponding to the prismatic strength, as well as main cracks that appeared under conditions of long-term step loading are highlighted. Variants of more accurate measurements are proposed. Development and implementation of the new standard GOST "Concretes. Methods for determination of complete diagrams" on the basis of the developed method for obtaining complete diagrams of concrete deformation under compression for the evaluation of ultimate deformability of concrete under compression are necessary.

Sorption of Se (IV) from aqueous solutions with subsequent determination by X-ray fluorescence analysis

2020 ◽  
Vol 86 (10) ◽  
pp. 5-9
Author(s):  
D. G. Filatova ◽  
A. A. Arkhipenko ◽  
M. A. Statkus ◽  
V. V. Es’kina ◽  
V. B. Baranovskaya ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Fluorescence Analysis ◽  
Standard Samples ◽  
Phase Contact Time ◽  
Sorbent Phase ◽  
X Ray ◽  
Fundamental Parameters ◽  
Inductively Coupled ◽  
Subsequent Determination

An approach to sorptive separation of Se (IV) from solutions on a novel S,N-containing sorbent with subsequent determination of the analyte in the sorbent phase by micro-x-ray fluorescence method is presented. The sorbent copolymethylenesulfide-N-alkyl-methylenamine (CMA) was synthesized using «snake in the cage» procedure and proven to be stable in acid solutions. Conditions for quantitative extraction of Se (IV) were determined: sorption in 5 M HCl or 0.05 M HNO3 solutions when heated to 60°C, phase contact time being 1 h. The residual selenium content in the solution was determined by inductively coupled plasma mass spectrometry (ICP-MS) using 82Se isotope. The absence of selenium losses is proved and the mechanism of sorption interaction under specified conditions is proposed. The method of micro-x-ray fluorescence analysis (micro-RFA) with mapping revealed a uniform distribution of selenium on the sorbent surface. The possibility of determining selenium in the sorbent phase by micro-RFA is shown. When comparing the obtained results with the results of calculations by the method of fundamental parameters, it is shown the necessity of using standard samples of sorbates to obtain correct results of RFA determination of selenium in the sorbent phase.

EXPERIMENTAL STUDIES OF REINFORCED CONCRETE STRUCTURES WITH CROSS-SHAPED SPATIAL CRACK UNDER TORSION WITH BENDING

2020 ◽  
Vol 92 (6) ◽  
pp. 13-25
Author(s):  
Vl.I. KOLCHUNOV ◽  
◽  
A.I. DEMYANOV ◽  
M.M. MIHAILOV ◽  
◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Experimental Determination ◽  
Calculation Method ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Design Parameters ◽  
Reinforced Concrete Structures ◽  
Experimental Scheme

The article offers a method and program for experimental studies of reinforced concrete structures with cross-shaped spatial crack under torsion with bending, the main purpose of which is to check the design assumptions and experimental determination of the design parameters of the proposed calculation method. The conducted experimental studies provide an opportunity to test the proposed calculation apparatus and clarify the regularities for determining deflections, angles of rotation of extreme sections, and stresses in the compressed zone of concrete. For analysis, the article presents a typical experimental scheme for the formation and development of cracks in the form of a sweep, as well as characteristic graphs of the dependence of the angles of rotation of end sections.

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