STUDY ON THE MECHANICAL PROPERTIES OF CFRP CIRCUMFERENTIALLY CONFINED CONCRETE FILLED STEEL TUBE COLUMN OF MARINE STRUCTURE UNDER COMPRESSION-BENDING-TORSION COMBINED LOAD

In order to study the mechanical properties of CFRP circumferentially confined concrete filled steel tube column under combined compression-bending-torsion load, pseudo-static tests were conducted, including 4 CFRP circumferentially confined concrete filled steel tube columns and 2 concrete filled steel tube columns. The number of CFRP layers and axial load ratio were studied. The failure modes and the load-deformation hysteretic curves under bending-torsion and compression-bending-torsion load were obtained. The experimental results showed that the failure mode of CFRP circumferentially confined concrete filled steel tube column was bending failure and the process could be summarized as:the local buckling of steel tube initialed in plastic hinge area and circumferential cracks of CFRP appeared, then CFRP ruptured and was peeled off steel tube, and the steel tube finally cracked in the buckling region. The existence of axial force made the failure mode of steel tube more likely to be the "elephant leg" type. CFRP confinement had little effect on the bearing capacity and ductility of concrete filled steel tube under bending-torsion load. For CFRP circumferentially confined concrete filled steel tube columns subjected to compression-bending-torsion load, CFRP confinement can improve the ductility and energy dissipation capacity of concrete filled steel tube effectively, and it can delay stiffness degradation despite of little improvement of the bearing capacity. Furthermore, the energy dissipation capacity of members increased with the increasing CFRP layers as the local buckling of the steel tube was restricted effectively.