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.
Main parameters, which characterize shear strength, are crack distribution, width of diagonal crack opening and angle of inclined crack. There are in this article, comparison crack resistant of testing reinforced concrete (RC) beams on the shear with such variable parameters like presence or absence internal reinforcement, different shear span, and presence or absence external composite reinforcement. Shear span (relative span to effective depth ratio) was acquired the following values: a/d=2, 1.5, 1. For internal reinforcement, rebar’s A240C with diameter 8 mm and steps 100 mm was chosen. The composite FRCM system was like external reinforcement with three stripe of composite fabric with width 70 mm and step 100 mm. Eight RC beams were tested. After testing, we discovered that the most influenced on the serviceability capacity was shear span. Internal transverse reinforcing increased shear strength on the same level and it was independent from shear span and other factors. Only quantity of reinforcing determine level of increasing shear capacity. FRCM system is efficient strengthening system, which significant increase shear crack resistant for RC beams. External FRCM reinforcing increase shear crack resistance on the same percentage and independent from presence or absence internal reinforcement.
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.
In this article, results of experimental testing of reinforced concrete beams without transverse shear reinforcement are given. Three prototypes for improved testing methods were tested. The testing variable parameter was the shear span to the effective depth ratio. In the result of the tests we noticed that bearing capacity of RC beams is increased with the decreasing shear span to the effective depth ratio. The design method according to current codes was applied to test samples and it showed a significant discrepancy results. Than we proposed the improved design method using the adjusted value of shear strength of concrete CRd,c. The results obtained by the improved design method showed satisfactory reproducibility.
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 describes 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.
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 re-bars has been described.
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 ex-tremely 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.