Introduction. Reinforcement methods, which are mainly used in domestic practice to strengthen metal structures, based on adding an additional section to metal elements by bolting or welding them. These methods, of course, are reliable and effective, but they cannot always be applied when it is necessary to preserve not only the building as a whole, but also its original internal and external appearance. Moreover, metal elements increase the stress on the structure and the building as a whole and are susceptible to corrosion and fatigue. There are often cases when it is difficult to fix a reinforcement element to the main structure, both from a technological and constructive point of view. In these situations, it becomes necessary to reinforce metal structures with high-strength materials with low weight and high manufacturability. Among the various strategies for reinforcing structures, bonding of high-strength composite carbon materials (FRP — Fiber-reinforced polymer) is becoming more and more popular in the world, especially for reinforced concrete structures, although application to metal structures is also quite common in Europe. But it should be noted that in Ukraine, unfortunately, this material is not yet widely used to strengthen metal structures. Problem Statement. The restoration of metal structures becomes necessary every time there are design, manufacturing or construction errors. Strengthening is also necessary in cases of long-term operation of buildings without timely maintenance and major repairs, insufficient strength of structural materials, as well as changes in weather conditions and current regulatory documents in Ukraine. So there is a need to strengthen metal structures with the most effective methods, both from the point of view of the reliability of building structures and from the point of view of profitability, which is influenced by the long shutdown of enterprises and the halt of the production process to carry out reconstruction work. Purpose. Investigate a modern method of reinforcing metal structures using high-strength carbon fibre-reinforced polymer (CFRP) materials in order to increase the bending capacity of a metal structural element, in particular, to check the reliability of adhesion of a metal beam to a reinforcing layer of TM «Mapei» composite material, which is glued using epoxy-based glue. Methods of research. Experimental testing of metal I-beams reinforced with external reinforcement by gluing high-strength carbon-based material (CFRP) TM «Mapei» by means of a static concentrated load in the middle of the beam span. Results. By analyzing the results of the experimental test, data were obtained indicating that after the inclusion of the carbon fibre-reinforced polymer in the operation, the percentage decrease in vertical deflection at a load of 75 kN was 39.5 %, and the value of the prmissible load, taking into account the stiffness condition (checking of building structures the established conditions of limiting deflections), increased by 11.8 %. When testing the phenomena of delamination of the composite from the base was not detected. Conclusions. Reinforcement of steel beams with a carbon fibre-reinforced polymer material led to a decrease in element deformations and, as a consequence, to the possibility of increasing the bearing capacity. An experimental test confirms the theoretical calculations to maximize the bearing capacity of a metal beam using the fibre-reinforced polymer material. A significant effect from the reinforcement of metal structures with composite materials can be achieved when strengthening the building structures of large-span buildings and structures, when reinforcing by traditional methods, they require complex design solutions, high labor costs, stopping the production process to perform reinforcement work, when the weight of the reinforcing structure is often significant.
Sonotrodes for Ultrasonic Welding of Titanium/CFRP-Joints—Materials Selection and Design
