The aim of the research was to check the possibility of using the non-destructive method of acoustic emission to assess the condition of concrete without dispersed reinforcement and with various additions of curved steel fibres, during three-point bending. An important aspect of the research proposed in the article is the use of a hybrid method of analysis, which involves complementing the results of strength tests, the results of numerical calculations and the results of strain distributions recorded with a digital image correlation system (DIC System, in this research GOM Suite optical system). The operation of the concrete material under load, depending on the amount of fibres added, is reflected in the recorded acoustic emission (AE) signals. The differences concern the number of signals of individual classes and their distribution over time. The differences exist for both low and high load values, which confirms the possibility of using the acoustic emission method to monitor the condition of the material. It was shown that the numerically determined effective stress levels decreased as the proportion of steel fibres in the concrete increased, while the maximum levels of the first principal stresses increased. During the analyses, a preliminary comparison of the deformation results obtained using the finite element method and the DIC System was also carried out.

Concrete structures that are influenced by degradation, overloading, the thawing, and freezing cycles, corrosion of reinforced bars, should be repaired or strengthened. Each of the mentioned influences lead to decreased load-carrying capacity of the structure or its member. Exceeding the load-carrying capacity leads to mechanical damage of members or excessive deformation. The damaged member has to be strengthened to the required level of reliability and load-carrying capacity. There exist many types and methods of strengthening the columns. This research work deals with strengthening of columns by concreting a new layer of fiber concrete. When applying that type of strengthening, it is necessary to assure the contact between the old layer and the new one. The paper deals with analysis of different types of contacts and determination of their parametric values.

Bridge structures are exposed to various environmental loads, which cause gradual degradation of the construction materials. A detailed diagnosis of the actual condition of the existing bridge structure is therefore very important in order to determine the actual degradation of materials, structural failures, and their impact on the reliability, durability, and load-carrying capacity of the bridge structure as reliably and accurately as possible. Many bridges are not even known for their age, when they were built, or in what condition they are. Sometimes they can be old and historical bridges, and we don’t even know about it. Some of these bridges are still in use and deserve our attention. If there is no information about these bridges, their historical significance is not known, they are often unnecessarily demolished and replaced with new bridges instead of being preserved and reconstructed. One such bridge is a masonry brick arch bridge (vault bridge) on the local road in the village Rúbaň, Slovakia. The research determined the age of the bridge, which is estimated to be more than 200 years old and is still functional. Therefore, this bridge also deserves attention, and its span does not matter. The paper focuses on the diagnosis and evaluation of a historical short-span masonry arch bridge. The task was to verify its condition, detect defects, determine the load-carrying capacity and evaluate its possible further use for transport on the bridge. This was done to prove the historical significance of the bridge and to preserve it for future generations instead of demolishing it.