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1
Content available Stress-strain state of damaged reinforced concrete bended elements at operational load level
Kopiika Nadiia, Vegera Pavlo, Vashkevych Rostyslav, Blikharskyy Zinoviy
Production Engineering Archives
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2021
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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.
2
Content available remote Optimized electroless Ni-Cu-P coatings for corrosion protection of steel rebars from pitting attack of chlorides
Mukhopadhyay Arkadeb, Sahoo Sarmila
Engineering Transactions
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2021
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Vol. 69, iss. 3
315--332
EN
Structures, constructions and bridges in coastal areas are greatly affected by the corrosive attack of chlorides. This reduces their lifetime and leads to losses due to their maintenance. This study aims to improve the lifetime and corrosion-proof behavior of steel rebars in the saline environment (3.5% NaCl) by applying electroless Ni-Cu-P coatings with high corrosion resistance. Ni-Cu-P coating was deposited on Fe-600 steel rebars. The coating was deposited by varying bath condition parameters, such as concentration of nickel sulphate, sodium hypophosphite and copper sulphate. This led to a variation in Ni, P and Cu content, and finally, the optimal bath combination was obtained using the Taguchi-based grey relational analysis. For concentrations of 25, 10 and 0.3 g/l nickel sulphate, sodium hypophosphite and copper sulphate, enhanced corrosion resistance of the coated rebars could be achieved with −350 mV Ecorr and 0.4 µA/cm2 Icorr. At the same time, the bare rebars had Ecorr of − 653 mV and Icorr of 11.7 µA/cm2 . .
3
Content available Non-uniform corrosion of steel rebar and its influence on reinforced concrete elements` reliability
Blikharskyy Yaroslav, Kopiika Nadiia, Selejdak Jacek
Production Engineering Archives
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2020
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Vol. 26, Iss. 2
67--72
EN
Remarkable place of reinforced concrete structures in construction field has been noted in wide number of recent researches. Subsequently, their degradation due to aggressive environment has become the topical problem nowadays. Therefore, the formulation of reliable technique for corroded element strength decrement is of great importance, and could be achieved only with the use of complex experimental and theoretical analysis. In this article an attempt is made to propose the mathematical approach to corrosive process modelling, taking into consideration the specifics of its development. According to thorough literature review on existing studies, main specifics of the process were indicated for further suppositions and assumptions formulation. Accordingly, the complex theoretical investigation with corresponding mathematical computations was conducted and results of analytical modelling were discussed. As the initial data for analytical modelling results of previously conducted experiments were used. Analysis of the obtained results shows rather high correspondence with the real conditions of structural element exploitation, taking into consideration material anisotropy and complexity of the corroded zone spread along the rebar cross-section. Proposed methodology for limit force decrease evaluation in general demonstrates reliable results and could be used for further evaluation of corrosion impacts on reinforced concrete elements bearing capacity.
4
Content available Investigating the factor of safety for the design of columns using properties of steel rebar’s manufactured in Pakistan
Zaidi Safdar Abbas, Saeed Muhammad Arsalan, Haider Farhan
Archives of Civil Engineering
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2020
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Vol. 66, nr 4
61--78
EN
This paper includes the behaviour of RC column, using the steel strength data employed by Rafi et al. (2014). Eccentric short columns are studied for this purpose, both tension and compression controlled sections, are analysed considering the current design practice of Pakistan. Three cross sections were analysed using different steel percentages against load-moment interaction and the strength analyses. Concrete strength is also varied in this analysis. The load moment interaction diagrams were observed in major and minor axes and strength analysis is made for compression controlled and tension controlled sections. In this analysis it is observed that a section designed as a tension controlled is giving brittle failure at certain limit which should be avoided. Considering this scenario, several random cross sections are analysed, strength reduction factors for eccentric and pure axial columns are computed. Conclusions are made on behalf of this analysis for different types of column design.
5
Content available remote Wpływ wilgotności betonu na naprężenia przyczepności pomiędzy betonem i stalą zbrojeniową
Uryzaj A.
Materiały Budowlane
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2016
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nr 11
106--107
PL
W artykule przedstawiono modele analityczne pozwalające na wyznaczenie maksymalnych naprężeń przyczepności pomiędzy betonem i stalą uzależnione od średnicy prętów zbrojeniowych, wytrzymałości betonu na ściskanie oraz jego wilgotności. Modele dotyczą coraz rzadziej stosowanych obecnie prętów gładkich oraz prętów żebrowanych. Równania zostały opracowane na podstawie wyników uzyskanych z badań własnych wykonanych metodą „pull-out” wyciągania zabetonowanych prętów zbrojeniowych. Badania przeprowadzono na betonie zwykłym klasy C30/37 w trzech stanach wilgotności – całkowicie suchym, powietrzno-suchym oraz pełnego nasycenia betonu wodą pod normalnym ciśnieniem atmosferycznym. W badaniach wykorzystano pręty zbrojeniowe o dwóch średnicach, różnych klas. Uzyskane wyniki badań wykazały istotny wpływ wilgotności betonu na jego przyczepność do prętów zbrojeniowych. Dowiedziono również, że wpływ wilgotności betonu na naprężenia przyczepności zależy od poziomu obciążenia oraz od rodzaju prętów, a zależność pomiędzy naprężeniami przyczepności a wilgotnością betonu jest wyraźnie nieliniowa.
EN
In the present paper analytical models allowing to determine the maximal bond stress between concrete and rebars depending on rebar diameter, concrete compressive strength and moisture content in concrete are presented. The models were derived for less and less frequently used plain bars as well as for ribbed bars. The equations were formed basing on results of self made pull-out test for rebars cast in concrete. The experiments were carried out for ordinary concrete of C30/37 class in three states of moisture content: the dry state, the airdry state and the full saturation state under the normal atmospheric pressure. Rebars of two diameters and two different steel classes were analysed. The results proved a significant influence of moisture content in concrete on its bond to rebars. It was also shown that the moisture content influence depends on loading level and rebar type and that the relation between bond and moisture content is non-linear.
6
Content available remote Posadzki przemysłowe ze zbrojeniem zwykłym lub/i rozproszonym
Musiał M., Styś D.
Materiały Budowlane
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2014
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nr 6
60--61
PL
W artykule porównano posadzki betonowe zbrojone prętami lub/i włóknami stalowymi oraz wskazano zakres ich stosowania. Na podstawie własnych doświadczeń opisano typowe defekty.
EN
In the paper concrete ground floors reinforced with steel rebars or/and fibres were compared. The range of their applicationwas specified. On the basis of own experiences typical defects were described.
7
Content available remote Przebieg korozji chlorkowej zbrojenia w betonie, bezpośrednio po inicjacji
Jaśniok T., Słomka-Słupik B., Zybura A.
Cement Wapno Beton
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2014
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R. 18/80, nr 3
158--165
PL
Przedstawiono badania próbek z pojedynczym prętem zbrojeniowym, próbki po procesie inicjacji korozji stali w roztworze NaCl suszono w warunkach laboratoryjnych. Elektrochemiczne badania polaryzacyjne wykazały malejącą wykładniczo gęstość prądu korozyjnego w funkcji czasu suszenia. Na podstawie badań pod mikroskopem elektronowym stwierdzono, że przyczyną sukcesywnego zmniejszania się szybkości korozji zbrojenia w betonie było malejące stężenie wolnych jonów chlorkowych, w roztworze w porach betonu. Było ono spowodowane głównie przez krystalizację uwodnionego chlorku żelaza(II), która zachodziła w czasie suszenia próbek.
EN
In the paper the research on specimens with a single rebar, that after the process of steel corrosion initiation by cyclic wetting in chloride solution and exposed to the constant conditions of temperature and humidity, is presented. Electrochemical polarization tests have shown exponentially decreasing corrosion current density over time. However, under microscopic examination, it was found, that the cause of the gradual decrease in the rate of corrosion of rebar in concrete was not sealing action of corrosion products, but decreasing concentration of chloride ions at the surface of the steel, mainly due to their bonding in corrosion product, mainly as hydrated iron(II) chloride, during samples drying.
8
Content available remote Modelowanie wpływu warunków klimatycznych na szybkość korozji zbrojenia w betonie
Krykowski T., Zybura A.
Cement Wapno Beton
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2014
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R. 18/80, nr 3
166--173
PL
Opracowano oryginalny model wyznaczania czasu inicjacji korozji zbrojenia oraz gęstości prądu korozyjnego, uwzględniający wpływ temperatury i wilgotności środowiska, określający warunki ekspozycji konstrukcji żelbetowej. Przeprowadzone obliczenia, z zastosowaniem nowego modelu, wykazały że zmiany środowiska nie mają większego wpływu na czas inicjacji korozji. Natomiast gęstość prądu korozyjnego, a więc szybkość korozji może różnić się bardzo znacznie, nawet o 100%, od przypadku, w którym założono stałe warunki otoczenia. Odwrotnie grubość otuliny betonowej na prętach zbrojeniowych nie ma wpływu na gęstość prądu korozyjnego, a więc na postęp korozji stali, po jej zapoczątkowaniu.
EN
The original model of the time of the steel reinforcement corrosion initiation in concrete and the density of corrosion current was proposed, taking into account the effect of temperature and humidity of the environment, in which the construction is exposed. The calculation, according to the new model, has shown that the corrosion initiation time is not significantly influenced. However, the density of corrosion current, thus the rate of this process, can differ significantly, even 100%, from the case in which the constant climate conditions was assumed. Contrary the thickness of the concrete cover on steel bars has no influence on the density of corrosion current, thus of corrosion development, after its initiation.
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