Research on structural design optimization and mechanical properties of concrete-filled steel tubular pier column

To enhance the bearing capacity of conventional concrete-filled steel tubular columns and meet the requirements of roadside support structures in underground roadways with heights ranging from 2.5 to 3.0 meters, an internally reinforced steel concrete-filled steel tubular pier column was proposed. Specific design parameters for concrete-filled steel tubular columns with appropriate length-to-diameter ratios were developed to suit the conditions of underground roadways. Comparative experiments were conducted to evaluate the mechanical properties of conventional and internally reinforced concrete-filled steel tubular short columns, and the axial compression performance of concrete-filled steel tubular long columns was also studied. The results indicate that the internally reinforced concrete-filled steel tubular pier columns exhibit reduced local buckling and core concrete damage compared to conventional concrete-filled steel tubular pier columns. These columns demonstrate smaller lateral and longitudinal deformations, slower failure progression, and superior ductility. Additionally, the ultimate bearing capacity of the internally reinforced concrete-filled steel tubular pier column is 500 kN higher than that of its conventional counterpart. For concrete-filled steel tubular long columns, the elastic limit strain ranges from 0.1% to 0.6%, while the plastic limit strain ranges from 2.0% to 6.7%. However, the bearing capacity of concrete-filled steel tubular long columns decreases significantly with an increasing length-to-diameter ratio, and their failure mode is characterized by pronounced buckling deformation. These findings provide valuable insights for optimizing the structural design and improving the mechanical performance of concrete-filled steel tubular pier columns.