Effects Of Long-Term Loads On The Behaviors Of FRP-Confined Concrete Columns

FRP(Fiber Reinforced Plastic)-confmed concrete columns are susceptible to creep and shrinkage, which is common phenomenon in concrete structures. A series of specimens with circular sections were tested, which included the short-term behavior of 24 FRP-confmed concrete specimens under different load eccentricities and the long-term behavior of eight FRP-confined concrete columns under different load ratios. An attempt to predict the time-dependent behavior of FRP-confined concrete columns and beam columns with circular sections is proposed by the ACI209(1997) Specifications model. A comparison of results calculated using this model shows good agreement with those of test. Based on the theoretical model, influences of the changing time immediately after loading, time under sustained loading, strength of the materials, load ratio, FRP ratio, slenderness ratio and load eccentricity ratio on the long-term effects are discussed. An attempt to predict the stress-strain relations of the core concrete after sustaining axially of eccentrically compressive load by means of a model that is proposed. The load-deformation behavior of the FRP-confined concrete columns and beam-columns is analyzed. Based on the theoretical model, influence of slenderness ratio, the changing FRP ratio, strength of the FRP composites and the concrete as well as load eccentricity ratio on the bearing capacity of the members after sustained load is discussed. Finally, simplified calculating method of the reduction factor for the bearing capacity of circular FRP-confined concrete beam-columns with long-term effects considered is suggested. The achievements in this paper may be referred for practical engineering.