Strength of bending concrete filled steel elements of improved design

An improved design of concrete filled steel tube element of rectangular cross-section subjected to bending has been proposed, which has greater strength and requires significantly greater energy consumption for destruction compared to known analogues. To test the effectiveness of the proposed design, experimental studies were carried out on the strength of normal sections and the beam rigidity of concrete filled steel tube beams under four-point bending. Research has shown that by simultaneously strengthening the compressed and tensile zones, it was possible to increase the strength of normal sections of beams. The increase in strength of beams of the improved design averaged 42%. The rigidity of non-reinforced concrete filled steel tube beams turned out to be significantly higher compared to beams without filling the steel pipe with concrete. In the improved beams, the stiffness was still approximately 20% higher. The results of comparing the calculated strength of concrete filled steel tube beams using the limit force method with experimental data indicate their satisfactory agreement.