MECHANICAL PERFORMANCE OF CONCRETE-FILLED SQUARE STEEL TUBE STIFFENED WITH PBL UNDER BENDING

To study the mechanical performance of concrete-filled square steel tube stiffened with PBL under bending, this paper describes a comparison test study on the mechanical behavior of three types of concrete-filled square steel tube structure under bending. The first type is concrete-filled square steel tube, the second type is concrete-filled square steel tube with steel plate stiffening rib, and the third type is concrete-filled square steel tube with PBL stiffening rib. The influences of aperture size and spacing of PBL were also investigated. Test results indicate that the failure mode of the first type specimen was single wave buckling, the failure modes of the other two were double wave buckling. Concrete crack distribution of the third type specimen was more uniform, and the width and spacing were smaller, showing steel tube and concrete worked together better. The bending capacity improved by PBL stiffening rib was not obvious, but the bending rigidity was increased by about 20% compared with the first type specimen. Whether the steel plate rib has pore or not had little effect on the rigidity of specimens. FEA results demonstrate that the bending capacity increased with the increase of the height and width of PBL stiffening rib, but decreased with the increase of relative pore diameter d₀, and the influence of pore spacing on bearing capacity was very small. Based on the test and FEA results, a simplified calculation method of concrete-filled square steel tube with PBL stiffening rib was proposed, and the value of relative pore diameter and relative pore spacing were recommended as 0.5 and 2.0 respectively in practical project.