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1
Content available Research into glue materials for repairing the cross-section of RC beams
100%
Blikharskyy Z.
Budownictwo o Zoptymalizowanym Potencjale Energetycznym
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2019
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tom Vol. 8 Nr 2
63--68
EN
In this article, the results of glue material regarding concrete connections between existent and new concrete bonds are presented. The basic experimental studies into selecting the optimal bonding layer involved testing 100 × 100 × 100 mm concrete cubes. These cubes modeled so-called “old” concrete constructions. Because most of the currently used reinforced concrete structures that require reinforcement or restoration were made decades ago, most of them do not contain chemical additives and multi-fractional concrete, so the concrete composition was adopted in the proper way, namely ordinary heavy concrete in 1970-1980. As a result of the experimental testing of concrete specimen restoration by means of a clamp arrangement, it is established that the maximum compatible work of “old” and “new” concretes is ensured by the use of bonding layers of specially modified mineral materials and the use of concretes using superplasticizers and a selection of their fractional composition.
PL
Przedstawiono wyniki badań dotyczące połączeń kleju betonowego między istniejącym a nowym spoiwem betonowym. Podstawowe badania eksperymentalne mające na celu wybranie optymalnej warstwy wiążącej obejmowały testowanie kostek betonowych 100 × 100 × 100 mm. Na kostkach tych zamodelowana została tak zwana „stara” konstrukcja betonowa. Ponieważ większość obecnie stosowanych konstrukcji żelbetowych, które wymagają zbrojenia lub renowacji, została wykonana kilkadziesiąt lat temu, większość z nich nie zawierała dodatków chemicznych i wielofrakcyjnego betonu, a więc skład betonu został przyjęty w odpowiedni sposób, a mianowicie jako zwykły ciężki beton z lat 1970-1980. W wyniku przeprowadzonych badań odtworzonych próbek betonu za pomocą układu zaciskowego ustalono, że maksymalne kompatybilne działanie „starych” i „nowych” betonów jest zapewnione przez zastosowanie warstw wiążących ze specjalnych modyfikowanych materiałów mineralnych oraz wykorzystanie betonów z superplastyfikatorami i dobór ich odpowiedniego składu frakcyjnego.
2
Content available Influence analysis of the main types of defects and damages on bearing capacity in reinforced concrete elements and their research methods
51%
Lobodanov М. , Vegera P. , Blikharskyy Z.
Production Engineering Archives
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2019
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tom Vol. 22
24--29
EN
In current economic trends, changes in construction using are required. It usually leads to changes in value and type of the working load on building structures, with the requirement to rate the technical state and replace or strengthen the elements. An important aspect of determining the residual bearing capacity of damaged bending reinforced concrete elements is the research concerning the influence of difference defects and damages on the change of strength and deformability. In the article main types of damages and defects, methods of studies of damaged reinforced concrete elements and the expediency of usage of this elements are described. However, most methods are suitable only for certain defects and damages due to the large complexity of calculations and the consideration of multifactoriality. Significant complexity of a single method for calculating damaged elements depends on the possible changing stress strain state of an element in combination with certain defects and damages, the presence of a non-complete separation where during loading or alteration of the damaged element the fractions become included in the work, reinforced concrete is the composite material which carrying complexity in calculating the joint work of its components.
3
Content available Corrosion of RC beams during time
51%
Blikharskyy Y. , Khmil R. , Blikharskyy Z.
Quality Production Improvement - QPI
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2019
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tom Vol. 1, Iss. 1
311--318
EN
This article presented results of impact corrosion on reinforce concrete beams during time with previous loading. Before testing the RC beams were loaded by 37% and 75% from bearing-capacity load of undamaged corrosion beams. There were tested two types of beams. First type beams were tested under force loading action and second type beams were tested under force loading and corrosion action. As an aggressive environment were used the 10% solution of sulfuric acid H2SO4. Such environment takes place in separate chemical manufactures, galvanic workshops, flue pipes of thermal power plants. The results of experimental studies have established that the effect of the aggressive environment with simultaneous loading significantly impairs the stress-strain state of reinforced concrete beams. Bearing capacity due to the yielding of reinforcement bars for specimens with the simultaneous action of aggressive environment and previous loading of 37% and 75% takes place on 51…53 and 58…60 days. The destruction of these specimens, by crushing compressive concrete, at previous loading 37% occurred after 75…79 and at previous loading 75% - after 79…88 days. The history loading does not impact significantly on beams failure, on finite deflections and timing exhaustion bearing capacity since the start of the simultaneous action of aggressive environment and loading.
4
Content available Stress-strain state of damaged reinforced concrete bended elements at operational load level
51%
Kopiika N. , Vegera P. , Vashkevych R. , Blikharskyy Z.
Production Engineering Archives
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2021
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tom Vol. 27, Iss. 4
242--247
EN
Each structure is exposed to different influences during operation. As a result, there are various defects and damages of these elements that affect their safe operation. The article presents the results of experimental studies of reinforced concrete beams with damages to stretched reinforcement made with and without initial load application. As the damages were accepted one or five Ø5.6 mm holes. In one case, the damage was made until the beam destruction (up to the 8.4 mm opening) Control samples of both series were destroyed due to crushing of the compressed zone of concrete. Samples that were damaged without initial loading collapsed due to rupture of the stretched reinforcement. The same type of failure was identified for damages at the operational load level.
5
Content available Investigation of defective reinforced concrete beams with obtained damage of compressed area of concrete
51%
Blikharskyy Z. , Lobodanov М. , Vegera P.
Production Engineering Archives
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2022
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tom Vol. 28, Iss. 3
225--232
EN
In the building industry, it is a frequent cause of damage to elements at different stages: during transportation, operation, installation, etc. Since replacing an element is not always possible due to various circumstances, it entails significant financial losses, logistics, and others. For this reason, the expediency of studying the effect of damage on the bearing capacity of reinforced concrete elements is growing. This effect is dependent on its type and has significant variability. In the case of the combination of the defect and damage in reinforced concrete elements, the complexity of the research of this element increases significantly. In this article is discussed: a review of damaged reinforced concrete elements; researching the influence of the damage and additional factors on the element; developed testing methodology for bending reinforced concrete elements with damage to concrete in a compressed zone with insufficient reinforcement, when performing damage to the action of the load and during the action of the load, is presented; the influence on the deformability and bearing capacity of the variability of damage on the sample with insufficient reinforcement is reflected, taking into account the factor of change in the load at which the damage is performed; a comparison is made of the dependence of the change in the actual height of the compressed zone on the change in the load on the elements; implementation of conclusions on the result of the study.
6
Content available Bearing capacity of reinforced concrete beams with and without damages of rebar
51%
Khmil R. , Blikharskyy Z. , Vegera P. , Kopiika N.
Production Engineering Archives
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2023
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tom Vol. 29, Iss. 3
298-303
EN
The article presents the results of the bearing capacity of reinforced concrete beams with and without damages of internal reinforcement. One of the main elements of the production of the reinforced concrete industry is beams. The analysis of the experimental tests showed that the bearing capacity of reinforced concrete beams with damaged tensile main reinforcement decreases according to control undamaged samples due to the reduction of the reinforcement cross-section. However, the bearing capacity of reinforced concrete beams with tensile main reinforcement Ø20А500C, damaged to the cross-section area equal the rebar Ø16mm is more on 3.7… 24.0% than the bearing capacity of reinforced concrete beams with undamaged Ø16mm rebar. This is due to the non-uniform material properties of used thermally strengthened reinforcement A500C. When during testing the tensile main reinforcement is damaged by drilling a hole, the most damages occur in the core with lower physical and mechanical characteristics. In contrast, the outer thermally strengthened layer with bigger physical and mechanical characteristics is damaged to a lesser extent. The analysis of the obtained results shows that during design of reinforced concrete beams with damaged, it is necessary to consider using thermally strengthened non-uniform steel A500C as tensile main reinforcement.
7
Content available Corrosion of RC elements` reinforcement and its influence on the stress-strain state
51%
Blikharskyy Y. , Kopiika N. , Blikharskyy Z.
Quality Production Improvement - QPI
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2020
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tom Vol. 2, Iss. 1
214--220
EN
The stress-strain state of reinforced concrete elements is rather complicated issue of scientific research, which integrates different factors, such as the load type, atmospheric conditions, various defects, damages, geometric deviations. It is commonly known that corrosion of reinforced concrete elements affects both the strength and deformation parameters of the structure significantly; thus, internal stresses` parameters are also influenced. Therefore, detailed theoretical investigation of this issue is the main goal of this article. The detailed literature review and thorough analysis was conducted concerning previous experimental and theoretical studies of the corrosion defects` influence on the reinforced concrete elements` stress-strain state. Existing data and results were systematized and analyzed. On the basis of provided research it could be concluded that the reinforced concrete elements` stressstrain state greatly depends on existing damages and impurities. The stress-strain state could be complicated on micro-scale due to material chemical and mechanical peculiarities; simultaneously on macro-scale the bearing capacity is of the structure could be reduced in general. In the articles existing methods for this issue simulation and evaluation are described and perspective fields for further research are identified. The practical significance of the article is due to complex approach to the research and multilateral identification of the main issue key points.
8
Content available The impact of the agressive acid environment on RC constructions
51%
Blikharskyy Y. , Khmil R. , Blikharskyy Z. , Shnal T.
System Safety : Human - Technical Facility - Environment
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2020
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tom Vol. 2, nr 1
223--229
EN
The main issue of the article is the corrosion of the reinforced concrete elements by the co-influence of the aggressive and power factors. The problem of corrosion is extremely actual one. Therefore the tests were carried out upon the specimens considering the corrosion in the acid environment, namely 10 % H2SO4. The acid environment H2SO4 was taken as a model of the aggressive environment. Conclusions concerning the corrosion model of the cross section and investigation of stress-strain state have been made. That material concerns the problem of the reinforced concrete corrosion as a whole construction. Reinforced concrete beams were tested with and without the co-action of the aggressive environment and power factor.
9
Content available Improvement method of calculation reinforced concrete beams on the shear strengthened FRCM system
51%
Blikharskyy Z. , Vegera P. , Vashkevych R. , Khmil R.
System Safety : Human - Technical Facility - Environment
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2020
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tom Vol. 2, nr 1
215--222
EN
Determination of shear-load-bearing capacity of reinforced concrete beams (according to the current normative documents), comprises particular recommended values, which do not depend on the parameters of the sample or load. This article de-scribes the methodology for determination the shear strength with suggestions for calculation the coefficient CRd,c and compressed element tilt angle Ѳ while reinforced concrete elements` calculation with the use of “truss model”. In order to confirm the methodology 4 reinforced concrete beams were tested. Tests were performed in order to investigate each particular inclined section separately. Variable parameter was the relative shear span a/d, with its values a/d=2, a/d=1,5 and a/d=1. Another parameter was the usage of composite strengthening system, made for relative shear span a\d=2. Samples were tested as single-span beams subjected to short-term loading. The calculation with the use only the values, given in norms showed significant divergence of results. Using the refined parameter values provided the convergence of results within 16-29% toward overestimation of the experimental data. The composite reinforcement system calculation showed the overestimation of 23%, which is within the same limits as for the control samples.
10
Content available Corrosion of reinforce bars in RC constructions
51%
Blikharskyy Z. , Selejdak J. , Blikharskyy Y. , Khmil R.
System Safety : Human - Technical Facility - Environment
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2019
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tom Vol. 1, nr 1
277-283
EN
In this article presented results of researching corrosion of steel bars in aggressive environment in time under loading. For researching were used special equipment. The experience and research works shown that steel bars in the crack cross-section area can be corrode. With increasing width of crack in re-bars and power of aggressive of environment increased the level of corrosion and decreased time of progress. The level of danger of corrosion in the crack in depend of specialty of steel bars. It is geometry parameters of steel bars and characteristic of corrosive behaviour. The general tendency of the influence of various defects on the strength of steels is widely studied experimentally and theoretically only for geometrically correct stress concentrators. For damages that are irregular in shape, such as corrosion ulcers, significantly less researching in each case must experiment to find their effect on the mechanical properties of steels. In this work the influence of simultaneous action of the aggressive environment and loading on strength of steel rebars has been described.
11
Content available The effect of air-entraining agent on the properties of mortars
45%
Blikharskyy Z. , Markiv T. , Sobol K. , Turba Y. , Selejdak J.
Archives of Civil Engineering
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2023
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tom Vol. 69, nr 3
147--156
EN
The effect of the air-entraining agent on properties of mortar mixtures as well as on the compressive strength of hardened mortars was the objective of this study. Such mortars contain a certain amount of evenly spread closed air-voids pores with dimensions of 0.02-0.05 mm. On the one hand, the presence of a large volume of such air bubbles results in the reduction of mechanical properties of mortar. On the other hand, the use of this technological approach improves rheological properties of mortar mixture. The effect of the air entrainment on the flow, density, volume of entrained air of mortar mixture and compressive strength of hardened mortar was established. Obtained results show substantial increasing in the mortar flow at cement to sand ratio 1:2 by 1.8 times. The further decrease of C:S ratio results in a slight increase of the flow and even negligible its decrease at C:S = 1:4 compared to the reference mortar. The increase of the volume of entrained air results in the decrease of the density and compressive strength of mortar, but improve the resistance to freezing/thawing cycles. The results of this study can be a guide for mortar mix design to choose the most appropriate mix proportion to produce economically efficient mortars.
PL
Celem badań był wpływ domieszki napowietrzającej na właściwości mieszanek zaprawowych oraz wytrzymałość na ściskanie zapraw. Zaprawy takie zawierają pewną ilość równomierne rozprowadzonych, zamkniętych porów powietrznych o wymiarach 0,02-0,05 mm. Z jednej strony, obecność dużej ilości takich pęcherzyków powietrza powoduje obniżenie właściwości mechanicznych zaprawy. Z drugiej strony, zastosowanie tego podejścia technologicznego poprawia właściwości reologiczne mieszanki zaprawy. Określono wpływ domieszki napowietrzającej na urabialność, gęstość, objętość wprowadzonego powietrza oraz wytrzymałość na ściskanie zaprawy. Uzyskane wyniki wskazują na znaczny, 1,8-krotny wzrost rozpływu zaprawy przy stosunku cementu do piasku 1:2. Dalsze zmniejszanie stosunku C:S powoduje niewielki wzrost urabialności, a nawet znikomy jego spadek przy C:S = 1:4 w porównaniu do zaprawy wzorcowej. Wzrost objętości wprowadzonego powietrza powoduje zmniejszenie gęstości i wytrzymałości na ściskanie zaprawy, ale poprawia mrozoodporność. Wyniki badań mogą być wskazówką przy projektowaniu zapraw, aby wybrać najbardziej odpowiednie proporcje mieszanki w celu wytworzenia ekonomicznie efektywnych zapraw.
12
Content available Crack resistance of RC columns strengthened by CFRP under 30% of uls loading
38%
Blikharskyy Y. , Khmil R. , Selejdak J. , Katunský D. , Tytarenko R. , Blikharskyy Z.
System Safety : Human - Technical Facility - Environment
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2023
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tom Vol. 5, iss. 1
36--45
EN
Nowadays, among many existing reinforced concrete (RC) columns, it is impossible to find samples that work only as centrally compressed members – their vast majority work as eccentrically compressed members. On the other hand, the significant volumes of reconstruction in Ukraine will require studies of the work of various RC structures strengthened under different load levels. In addition to choosing the method of strengthening itself, the relevant tasks will be studies of bearing capacity, crack resistance, reliability (including residual resource) of structures, etc. This article presents the method of crack resistance experimental study of eccentrically compressed RC members. The proposed method was tested on unstrengthened (ordinary) and strengthened (in a stretched zone) RC columns; the results of experimental studies for ordinary and strengthened samples were also obtained. The columns were strengthened with a composite material (from many carbon-fiber-reinforced polymers) – the Sika Carbodur S512 strip. The feature of the crack resistance study of columns was that they were strengthened under the initial load level of 30 %. As a result of experimental research on the samples strengthened under load, we stated that the width of the crack decreased on average by about 36 % (at the comparable values of the active load). In turn, the average maximum length of cracks decreased to about 50 % of the height of the cross-section (for unstrengthened samples, this value was approximately 80 %), and the eccentric compressive ultimate load was increased by about 33 %.
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