Reliable assessment and prediction of the technical condition of reinforced concrete structures require accurate data of the stress–strain state of the structure at all stages of loading. The most appropriate technique to obtain such information is digital image correlation. Digital image correlation is a class of contactless methods which includes the following stages: obtaining an image from a studied physical object, saving it in digital form, and further analysis in order to obtain the necessary information about the stress–strain state of the structure. In this research, a detailed analysis of theoretical and experimental findings of digital image correlations was conducted. In the article, the main areas of scientific interest and computational approaches in digital image correlation issues were identified. Moreover, comparative analysis of alternative non-contact techniques, which also could be used for diagnostics of RC structures’ stress–strain state was conducted. The novelty of the study consists of a thorough comparative analysis with the indication of specific features of digital image correlation, which determine its wide application among the other similar methods. On the basis of the conducted literature review, it can be seen that the digital image correlation technique has gone through multi-stage evolution and transformation. Among the most widely studied issues are: image recognition and matching procedures, calibration methods and development of analytical concepts. The digital image correlation technique enables us to study cracking and fracture processes in structural elements, obtaining the full field of deformations and stresses. Further development of image processing methods would provide more precise measuring of stress–strain parameters and reliable assessment of structural behavior.

Development of the procedure for the estimation of reliability of reinforced concrete beams, strengthened by building up the stretched reinforcing bars under load

The usage of carbon fiber-reinforced polymers (FRP) are described as modern methods of strengthening for reinforced concrete constructions. The advantage of these materials are the great corrosion resistance to environmental factors, high stiffness and strength and weight in comparison with other materials. The disadvantage of relatively high cost is offset by the cost reduction and labor when performing work on strengthening, by decreasing of performance time, by lack of needs to use the expensive equipment, installed and used without unloading the structures. This paper presents experimental results of 6 reinforce concrete columns strengthened by CFRP strips Sika Carbodur S512 with 50 mm width. The comparative analysis was carried out and strengthened effectiveness was determined for 2 unstrengthen control specimens, 2 specimens strengthened without initial load and 2 specimens strengthened at 1/2 of experimentally determined destructive efforts of the unstrengthen column.

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.

MATEC Web of Conferences, open access proceedings in Materials science, Engineering and Chemistry