concrete beams, strengthened by building up the stretched reinforcingbars under load . Eastern-European Journal of Enterprise Technologies, 5(7), (95), 32-42, DOI: 10.15587/1729-4061.2018.142750. Krainskyi, P., Blikharskyy, Y., Khmil, R., Blikharskyy, Z., 2018a. Experimental Study of the Strengthening Effect of Reinforced Concrete Columns Jacketed Under Service Load Level . Matec Web of Conferences, 183, 02008, DOI: 10.1051/matecconf/201818302008 Krainskyi, P., Blikharskyy, Y., Khmil, R., Vegera, P., 2018b. Influence of loading level on the bearing capacity of RC
The micro-fibers increase the consistency and uniformity of concrete, which can improve the protective properties of concrete cover and thus should reduce the corrosion of the reinforcement bars in the reinforced concrete elements. The article presents a study which main objective was to specify the effect on concrete mix the addition of steel or polypropylene micro-reinforcement fibers on the reinforcing bars corrosion process. The research included measuring the reinforcement corrosion progress caused by the chloride impact as well as cyclical freezing and thawing specimens test. To measure the electrochemical corrosion progress the non-destructive i.e. galvanostatic pulse method was used. The results were used to conduct a comparative analysis.
The carrying structure of the bridge over the Jiu River at Aninoasa consists in two parallel concrete arches with variable height of the cross section, sustaining a concrete deck through vertical concrete hangers. In the time period passed since the bridge was erected, some structural elements shown damages. In order to establish the technical state of the bridge, a technical appraisement was performed and according to this, the most exposed elements to the risk of failure are the hangers.
The purpose of this paper is to present briefly both, the method used to test the actual bridge carrying capacity in situ and the finite element model developed for the static and dynamic analysis of the structure.
In order to estimate the state of the structural elements, two ways were followed. In the first stage, a test project was carried out and in the second stage, a complete 3D finite element model was developed to analyze the bridge structure.
The test project has foreseen the loading of the bridge by heavy unloaded trucks, disposed in some positions on the deck and the measurements of the deck and arches displacements. The positions of the trucks were established in order to obtain the maximum values both for arches transverse displacements and vertical displacements of the deck. Using electro-resistive transducers the hangers elongations and strains values on their cross section were also measured. These measured values were compared with those obtained from the numerical calculations performed by using the complete finite element model. By means of the finite element model, also the response of the structure following the dynamic action of vehicles was investigated.
The article is devoted to the overall view of experimental research of reinforced concrete beams with the simultaneous influence of the corrosion environment and loading. The tests have been carried out upon the reinforced concrete specimens considering the corrosion in the acid environment, namely 10 % H2SO4 that have been taken as a model of the aggressive environment. The beams are with span equalling to 1,9m with different series of tensile armature, concrete compressive strength and different length of impact of corrosion (continuous and local). The influence of simultaneous action of the aggressive environment and loading on strength of reinforced-concrete beams has been described. For a detailed study of the effect of individual components there was suggested additional experimental modelling of the only tensile armature damage without concrete damage. It will investigate the influence of this factor irrespective of the concrete.
://www.germann.org/TestSystems/GalvaPulse/GalvaPulse.pdf , 2009. 15. Grzmil W., Raczkiewicz W., Evaluation of the effect of cement type on the carbonation of concrete and the corrosion of reinforcement in reinforced concrete samples. Cement Wapno Beton 22(4) (2017) 311-319. 16. Song H.W., Saraswathy V., Corrosion monitoring of reinforced concrete structures - A review. International Journal of Electrochemical Science 2 (2007) 1-28. 17. Raczkiewicz W., Effect of concrete addition of selected micro-fibers on the reinforcingbars corrosion in the reinforced concrete specimens. Advances in Materials Science 16(3) (2016) 38-46.
The composite bars have become a useful substitute for conventional reinforcement in civil engineering structures for which load capacity and resistance to influences of environmental factors' are required. Considering the requirements of responsible design of engineering structures with particular emphasis on durability, the use of non-metallic reinforcement in reinforced structural elements allows to reduce the costs related to erection of buildings, as well as the costs of building maintenance and renovations. The behaviour of model beams made of concrete reinforced with composite bars (fiber reinforced polymer bars) in three-point bending test was analyzed. The strength parameters of composite bars were tested. The bending capacity, deformation of concrete, and beam deflection were determined. Crack propagation in the model beams under load was analyzed using the Aramis 5M optical measuring system. Due to the strength characteristics of the composite reinforcing bars, the beams exhibited significant tensile strains, which resulted in the development of cracks of considerable width.
The use of inhibitors is one of the most practical means for protecting metals against corrosion, especially in acidic media. The interest is to use organic compounds as inhibitors due mainly to their inherent and non-toxic nature. Amino acids are attractive as corrosion inhibitors because they are nontoxic, relatively easy to produce with high purity at low cost, and are soluble in aqueous media. Lysine, one kind of amino acid is used as inhibitor. The aims of this study are to show corrosion protection efficiency of lysine and to explain the mechanism of corrosion. The experimental results demonstrated that the lysine offered protection for low alloy carbon steel in aggressive environments like H2SO4. Materials under investigation are two types of low alloy carbon steel marked as: Steel 39, Steel 44 (usually applied to concrete as reinforcing bars). The corrosion media consists in sulfuric acid in presence of chloride ions, in form of NaCl (H2SO4 1M + Cl- 10-3M). Potentiodynamic polarization methods are used for inhibitor efficiency testing. Potentiodymanic polarization measurements showed that the presence of lysine in acidic solution decreases the corrosion current to a good extent. The corrosion inhibition efficiency improves with the increase of the lysine concentration. The use of this inhibitor (1g/L) protects steel 39 in acidic media with 78.88% efficiency. That means lysine is a good corrosion inhibitor for these aggressive conditions.
The corrosion of metal surfaces causes huge financial damages to the industries annually, what has lead to an increase in the search for substances that can slow down or prevent corrosion rate. Green inhibitors which are biodegradable, without any heavy metals and other toxic compounds, are promoted. Amino acids are attractive as corrosion inhibitors because they are nontoxic. We have used methionine as corrosion inhibitor. Materials under investigation are two kind of low allow carbon steel marked as: Steel 39, Steel 44 usually applied to concrete as reinforcing bars, and manufacture in Elbasan. The inhibition effect of methionine on the corrosion behavior of low allow steel is investigated in sulfuric acid in presence of chloride ions, in form of NaCl (H2SO4 1M + Cl- 10-3M). Potentiodynamic polarization method is used for inhibitor efficiency testing. The pitting corrosion current shows that increasing concentration of the inhibitor causes a decrease in pitting current density, and inhibition efficiency increases with increasing concentration of the inhibitors.
Practical method for analysis and design of slender reinforced concrete columns subjected to biaxial bending and axial loads
Reinforced and concrete-encased composite columns of arbitrarily shaped cross sections subjected to biaxial bending and axial loads are commonly used in many structures. For this purpose, an iterative numerical procedure for the strength analysis and design of short and slender reinforced concrete columns with a square cross section under biaxial bending and an axial load by using an EC2 stress-strain model is presented in this paper. The computational procedure takes into account the nonlinear behavior of the materials (i.e., concrete and reinforcing bars) and includes the second - order effects due to the additional eccentricity of the applied axial load by the Moment Magnification Method. The ability of the proposed method and its formulation has been tested by comparing its results with the experimental ones reported by some authors. This comparison has shown that a good degree of agreement and accuracy between the experimental and theoretical results have been obtained. An average ratio (proposed to test) of 1.06 with a deviation of 9% is achieved.
REFERENCES ACI 318-05 (2005) Building Code Requirements for Structural Concrete and Commentary , American Concrete Institute, Farmington Hills, Mich. ACI Committee 408 (2003) Bond and Development of Straight ReinforcingBars in Tension , ACI 408R-03, American Concrete Institute, Farmington Hills, Mich. Azizinamini, A. – Chisala, M. – Roller, J. H.- Ghosh, S. K. (1995) Tension Development Length of ReinforcingBars Embedded in High-Strength Concrete , Engineering Structures, V. 17, No. 7, 1995, pp. 512-522. Azizinamini, A. – Darwin, D. – Eligehausen, R. – Pavel, P