Axial Compressive Behavior of Circular Bamboo Scrimber Column and Uhpc-Filled Square Steel Tube Columns

Abstract

The lightweight and high-strength circular bamboo scrimber core column was embedded in the core of a square steel tube-confined ultra-high performance concrete (UHPC), forming a circular bamboo scrimber column and UHPC-filled square steel tube composite column (CBUFST). Axial compression tests were conducted on 42 CBUFSTs, 6 UHPC filled square steel tube composite columns (UFSTs), and 6 bamboo scrimber filled square steel tube composite columns (BFSTs) to investigate the effects of parameters such as the diameter of the bamboo scrimber core and the thickness of the steel tube on the axial compressive performance of the composite columns. The test results show that the failure mode of the CBUFST was characterized by significant buckling deformation and corner cracking of the steel tube, and fragmentation of the interlayer UHPC. The bamboo core scrimber column exhibited rebound after unloading. As the ratio of bamboo scrimber increased, the peak load initially increased and then decreased, while the strength-to-weight ratio increased, axial stiffness decreased, and ductility nonlinearity increased. An increase in the ratio of steel improved the peak load and strength-to-weight ratio. Based on the experimental results, a theoretical model for the bearing capacity of the composite column was established, with the distribution parameter c for the equivalent confinement stress of the steel tube determined to be 0.635. The model was validated and found to accurately predict the bearing capacity. The materials in the composite column work synergistically, exhibiting characteristics of lightweight, good deformability, and high bearing capacity.The lightweight and high-strength circular bamboo scrimber core column was embedded in the core of a square steel tube-confined ultra-high performance concrete (UHPC), forming a circular bamboo scrimber column and UHPC-filled square steel tube composite column (CBUFST). Axial compression tests were conducted on 42 CBUFSTs, 6 UHPC filled square steel tube composite columns (UFSTs), and 6 bamboo scrimber filled square steel tube composite columns (BFSTs) to investigate the effects of parameters such as the diameter of the bamboo scrimber core and the thickness of the steel tube on the axial compressive performance of the composite columns. The test results show that the failure mode of the CBUFST was characterized by significant buckling deformation and corner cracking of the steel tube, and fragmentation of the interlayer UHPC. The bamboo core scrimber column exhibited rebound after unloading. As the ratio of bamboo scrimber increased, the peak load initially increased and then decreased, while the strength-to-weight ratio increased, axial stiffness decreased, and ductility nonlinearity increased. An increase in the ratio of steel improved the peak load and strength-to-weight ratio. Based on the experimental results, a theoretical model for the bearing capacity of the composite column was established, with the distribution parameter c for the equivalent confinement stress of the steel tube determined to be 0.635. The model was validated and found to accurately predict the bearing capacity. The materials in the composite column work synergistically, exhibiting characteristics of lightweight, good deformability, and high bearing capacity.

Keywords: Bamboo scrimber, Ultra-High-Performance Concrete (UHPC), Concrete-filled steel tube column, Composite Column, Theoretical model