ABSTRACT
The paper presents selected results of experimental research performed on steel - concrete composite beams. The study aimed at determining efficiency and technical feasibility of strengthening such structures. The main assumption was that strengthening was conducted under load, which is consistent with the factual state of the modernized structure. Beams were strengthened by welding sheet metal to increase the area of the steel section. The safe level of stress during welding and the appropriate order of joints were determined. The study focused on distortion caused by welding, cooling and shrinkage. Following the strengthening, the beams were overloaded, underwent plastic distortion and were ultimately damaged. The beams’ increased stiffness and capacity due to strengthening was monitored.
