Behavior of multicell concrete-filled round-ended steel tubes under bending

As an innovative composite structural element, concrete-filled round-ended steel tubes (CFRTs) exhibit remarkable application potential as piers and arches in civil engineering because of their low flow resistance coefficient and beautiful shape. Although pure bending loading may not be common, analyzing the flexural behavior is crucial to understand mechanical properties in complex loading scenarios. This study comprehensively investigated the bending property of multicell CFRTs (M-CFRTs) through a combined approach involving tests and finite element analysis. Eight specimens were tested to study the bending property of M-CFRTs. Detailed analysis of moment-curvature curves throughout the loading process revealed a remarkably ductile failure mode for all specimens. The composite action between the core concrete and steel tube was discussed and clarified on the basis of the experimental findings. In addition to experimental investigations, the ABAQUS program was employed to examine the flexural performance of M-CFRTs, including the moment-curvature curves, the development of stress distribution in a section, and the overall composite action. Moreover, the development of a neutral axis in the core concrete and steel tube was systematically probed. A slight bond slip was observed at the interface between the core concrete and steel tube. Lastly, a detailed analysis was conducted on the key parameters affecting flexural behavior, such as steel strength, concrete strength, cell number, steel ratio, and aspect ratio. The analytical results provide reference for the practical application of this structure.