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.

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.

scholarly journals Investigation of the relationship between the strength limit and the long time fatigue of steel reinforcements of reinforced concrete structures

2021 ◽  
pp. 28-40
Author(s):  
Denys Chernyshev ◽  
Yulia Makarenko ◽  
Tetiana Khomutetska ◽  
Valeriy Makarenko
Keyword(s):  
Reinforced Concrete ◽  
Crack Resistance ◽  
Hydrogen Content ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Reinforcing Steel ◽  
Term Operation ◽  
Strength Limit

The results of experimental studies have shown a strong effect of diffusion hydrogen on the static and cyclic parameters of crack resistance of reinforcing steel. It was found that with increasing flooding, especially when the hydrogen content exceeds 5 cm3/100g, both static strength and long-term strength (fatigue) decrease sharply. Moreover, these areas of hydrogen solution in reinforcing steel are characterized by a viscous nature of fracture, while for heavily flooded reinforcement (from 5 to 12 cm3/100g) is characterized by brittle fracture by the mechanism of microcracking in the hardened (martensite or troostite structure). The analysis of the obtained experimental results allowed to determine the optimal hydrogen content in the reinforcing steel (3…5 cm3/100g), the excess of which can cause a decrease in the crack resistance of the reinforcement during long-term operation, especially in corrosive environments. The mechanism of hydrogen influence on crack resistance of metal at static and alternating loading which consists in diffusion and dislocation movement of hydrogen in structure of a reinforcing core that as a result that causes strong flooding of steel and its embrittlement is offered. It is established that carbon and low-alloy sieves, which are characterized by ferritic-pearlitic and sorbitol structure provide high resistance, especially to long-term fatigue, and the transition to steels with a structure of martensite or tempered (transient structure of bainite) structure of bainite sharply reduces reinforcing steel, which makes it impossible to use in the manufacture of reinforcement involved in reinforced concrete structures designed for long-term operation (more than 50…60 years). Thus, the obtained diagram can be recommended to designers of reinforced concrete structures for hydraulic purposes, as it greatly facilitates the reasonable choice of reinforcement in the development of reinforced concrete structures for responsible and long-term use.

Determination of the Chemical Composition of Corrosion Defects on the Inner Surfaces of Hollow Reinforced Concrete Structures

2021 ◽  
Vol 887 ◽  
pp. 542-547
Author(s):  
A.S. Bryukhova ◽  
N.V. Volkova ◽  
A.A. Kuznetsov ◽  
A.Yu. Kuzmenko
Keyword(s):  
Reinforced Concrete ◽  
Chemical Composition ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Corrosion Products ◽  
Reinforced Concrete Structures ◽  
Corrosion Defects

The paper presents the results of experimental studies on the determination of corrosion products on the surface of reinforced concrete structures. This paper also discusses methods for creating samples with artificial electro corrosion under conditions close to real operation. The paper presents the results of testing samples using laser-inducted breakdown spectrometry (LIBS) devices.

STRENGTH OF BENT REINFORCED CONCRETE ELEMENTS WITH ZONE REINFORCEMENT MADE OF STEEL FIBER

2021 ◽  
Vol 93 (1) ◽  
pp. 85-95
Author(s):  
D.G. UTKIN ◽  
Keyword(s):  
Reinforced Concrete ◽  
Steel Fiber ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Dynamic Loads ◽  
Deformation Model ◽  
Reinforced Concrete Structures ◽  
Short Term ◽  
Fiber Layer ◽  
Concrete Elements

On the basis of theoretical and experimental studies, the assumptions and calculation method for flexible and compressed-curved reinforced concrete structures with zone reinforcement made of steel fiber operating under static and short-term dynamic loads are formulated. In the developed method for calculating the strength of normal and inclined sections, a nonlinear deformation model is implemented, which is based on the actual deformation diagrams of materials. To confirm the main results of this method, numerical and full-scale experimental studies of reinforced concrete beam structures reinforced with conventional reinforcement and a zone steel-fiber layer were planned and carried out. Experimental studies were carried out under static and short-term dynamic loads. As a result of the conducted experiments, data were obtained that characterize the process of destruction, deformation and crack formation of steel-reinforced concrete elements under such types of loading. The efficiency of fiber reinforcement of normal and inclined sections for increasing the strength and deformation characteristics of reinforced concrete structures is revealed.

scholarly journals Determination of chemical composition on internal surfaces of hollow reinforced concrete structures under the influence of corrosion

2020 ◽  
pp. 123-128
Author(s):  
A. S. Bryukhova ◽  
Keyword(s):  
Reinforced Concrete ◽  
Chemical Composition ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Corrosion Products ◽  
Emission Spectrometry ◽  
Reinforced Concrete Structures ◽  
Internal Surfaces ◽  
Laser Spark

The paper presents the results of experimental studies on the determination of corrosion products on the surface of reinforced concrete structures. Methods for creating samples with artificial electrocorrosion under conditions close to real operation are discussed. The results of testing samples with different degrees of corrosion using laser-spark emission spectrometry (LIBS) devices are presented. The test is carried out on two different devices, a LIBS setup and a portable American-made laser analyzer LIBZ-300pe

scholarly journals Deformability of Short Steel Reinforced Concrete Structures on Light Concrete

2018 ◽  
Vol 7 (3.2) ◽  
pp. 370 ◽  
Author(s):  
Oleksandr Semko ◽  
Viktor Dariienko ◽  
Vitaliy Sirobaba
Keyword(s):  
Reinforced Concrete ◽  
Sheet Metal ◽  
Experimental Research ◽  
Lightweight Concrete ◽  
Structural Parameters ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Steel Reinforced Concrete ◽  
Thin Walled

The calculation, modeling and experimental research of steel-concrete tubular elements made of thin-walled galvanized sheet metal and lightweight concrete have been carried out. The proposed type of structures can be used as a separate structure in the form of a column or a pillar, and one of the types of the reinforcement of a certain light structure. The basic technological and constructive requirements for manufacturing and further exploitation of structures are given. For determination of actual work’s indexes of constructions experimental research of standards are undertaken, and recommendations on adjustment of well-known calculation formulas of close constructions as for structural parameters are given. The design (modeling) was performed in MSC / Nastran software. An analysis of the proposed structures use is carried out with the corresponding conclusions. 

scholarly journals Long-Term Efficiency of Two Organic Corrosion Inhibitors for Reinforced Concrete

2010 ◽  
Vol 636-637 ◽  
pp. 1059-1064 ◽  
Author(s):  
E.V. Pereira ◽  
R.B. Figueira ◽  
Manuela M. Salta ◽  
I.T.E. Fonseca
Keyword(s):  
Reinforced Concrete ◽  
Environmental Conditions ◽  
Corrosion Inhibitors ◽  
Electrochemical Techniques ◽  
Concrete Structures ◽  
Concrete Slabs ◽  
Reinforced Concrete Structures ◽  
Reinforcement Corrosion ◽  
Organic Corrosion Inhibitors

In this paper the efficiency of two organic corrosion inhibitors, a migratory and an admixture inhibitor, was evaluated by electrochemical techniques in solutions simulating the interstitial electrolyte of concrete and on concrete slabs exposed to natural environmental conditions over a five-year period. From obtained results, the usefulness of the two products is discussed aiming its application in new structures to prevent chlorides induced corrosion and as a curative method for repairing reinforced concrete structures contaminated with chlorides and affected by reinforcement corrosion.

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