FRP-PVC管约束圆形截面钢筋混凝土组合柱滞回性能试验研究

6个FRP-PVC管约束圆形截面钢筋混凝土组合柱试件进行滞回性能试验，研究轴压比n、FRP横向包裹层数m和FRP类型对组合柱在低周往复荷载作用下的破坏模式、滞回特性、位移延性、能量耗散能力、承载力退化、刚度退化等性能的影响。试验结果表明，当外包FRP-PVC管开裂并退出工作时，试件承载力呈跳跃式下降，试件退化为钢筋混凝土柱，可将外包FRP-PVC管的开裂作为该类构件即将破坏的首次预警；所有试件的滞回曲线均较为饱满，捏缩现象不明显，滞回性能良好；试件的承载力退化不显著；轴压比的增大提高了试件的峰值荷载，同时延缓了刚度退化趋势，降低了试件的耗能能力；与BFRP包裹的试件相比，CFRP包裹试件的峰值荷载、耗能能力有所提高，刚度退化延缓；BFRP包裹层数的增加可以延缓试件刚度退化并提高其延性。

Experimental study on reinforced concrete columns confined by FRP-PVC tubes under reversed loading

This paper conducted an experimental study on the behavior of six circular reinforced concrete columns confined by FRP-PVC tubes under reversed loading. The design parameters included the axial force ratio, the number of layers of FRP and the type of FRP. The effects of design parameters on the seismic behavior, such as failure modes, hysteretic characteristics, ductility, energy dissipation ability, strength degradation, and stiffness degradation, were the emphasis of the investigation. The experimental results indicate that when the outer FRP-PVC tubes fracture or fail, the lateral bearing capacity will suddenly drop, and the members will be degraded to reinforced concrete ones, thus the fracture and failure of FRP-PVC tubes is regarded as the first alarming before failure of the specimens. Mid-span load-deflection hysteretic curves exhibit good hysteretic behaviors, and the strength degradation is not apparent for all specimens. The lateral peak load increases as the axial load ratio grows, while the stiffness degradation delays and the energy dissipation decreases. The specimen confined by CFRP shows higher lateral peak load, lower stiffness degradation and better energy dissipation capacity, compared with the specimen confined by BFRP. The ductility is improved as the number of layers of BFRP increase, while the stiffness degradation delays for all specimens.