海洋结构CFRP环向约束钢管混凝土柱在压弯扭荷载下的力学性能研究

为了研究CFRP环向约束钢管混凝土柱在压弯扭复合荷载下的力学性能，该文开展了4个CFRP环向约束钢管混凝土柱和2个钢管混凝土柱的拟静力试验，主要参数为CFRP层数和轴压比，得到了在弯扭、压弯扭两种荷载作用下柱的破坏模式和荷载-变形曲线。试验结果表明， CFRP环向约束钢管混凝土柱的破坏模式为弯型破坏，其破坏过程为:塑性铰区域钢管局部屈曲、CFRP形成环向裂纹，随后CFRP断裂、与钢管剥离，最后钢管局部屈曲部位开裂。轴力的存在会使得钢管更容易出现“象腿”破坏模式。在弯扭荷载下， CFRP环向约束对钢管混凝土的延性以及承载力提高不明显；在压弯扭荷载下， CFRP环向约束能有效提高钢管混凝土的延性及其耗能能力，减缓刚度退化，但对承载力的提高不明显。此外，增加CFRP层数能有效抑制钢管的局部屈曲，增强耗能能力。

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.