This article examines flexural reinforced concrete structures condition assessment process in existing buildings on the stage where the reinforcement stress is between the yield and the tensile strength. The research is made on V. Jokūbaitis proposed methodology directly measuring the compression zone height, allowing us to evaluate the behavior of reinforced concrete beam fracture sufficiently precisely. This paper confirms the hypothesis that, when reinforcement reaches yielding stress, elastic strain dominates in concrete‘s compression zone and it is reasonable to use triangular concrete compression zone diagram, without tensile concrete above crack evaluation. The methodology of reinforced concrete structures bearing capacity assessment according to limit normal section crack depth is proposed. There is established connection between bending moments, when reinforcement achieve yielding stress and tensile strength, which allows us to decide about structures bearing capacity reserve. The results are confirmed with experimental studies and calculated values obtained by methodologies based on different reduced stress diagrams of concrete‘s compressive zone.

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Due to the impact-echo defectoscopy tests of a massive block of underreinforced concrete steel bars of diameter 22 and 32 mm were detected. This fact is described in the paragraph, and results are provided through a visualization of b-scanning. The effect of a concrete cover layer and of the reinforcement diameter is clear on the sensitivity of the method. Because of various parameters of the reinforcement, impactors of a different ball diameter were employed. With a ball of diameter 12 mm, 8 mm and 5 mm reinforcement at the depth of about 50 to 60 mm was detected.KEY WORDS: Impact-echo, concrete, non-destructive testing of steel bar detection.

The paper reviews the so far known information about the properties of biological shielding concrete used in the containment vessel of nuclear power plants (NPP) and its behaviour when exposed to radiation. The damage of concrete caused by neutron and gamma radiation as well as by the accompanying generation of heat is described. However, there is not enough data for the proper evaluation of the negative impacts and further research is needed.