FRP约束钢筋混凝土柱中钢筋屈曲行为研究

通过FRP约束钢筋混凝土柱的单向和往复轴压试验,研究了外包FRP的断裂应变、刚度、以及加载方式对钢筋屈曲性能的影响。采用了两种不同的纤维材料:CFRP和PET FRP,二者具有不同的断裂应变(CFRP1.5%;PET FRP5%)。在试验分析的基础上,发展了考虑FRP侧向约束作用的弹性地基梁模型,该模型能够较好地分析FRP约束钢筋混凝土柱中钢筋屈曲行为。基于弹性地基梁模型和试验数据,提出了考虑FRP侧向约束作用的钢筋屈曲经验模型。并将该模型通过二次开发的方法写入OpenSees数值分析平台,对FRP约束RC柱的往复轴压行为进行数值分析,分析结果与试验结果吻合较好。研究成果可为精确分析FRP约束钢筋混凝土结构的抗震性能提供有力的工具。

Buckling Behavior of Steel Rebars Embedded in FRP-confined Concrete

This paper presents an experimental investigation on FRP-confined RC columns subjected to monotonic and cyclic compressive loading. The key parameters in this study are the rupture strain of FRP, jacket stiffness, and loading scheme. Carbon and PET FRPs were chosen for comparison because they possess very different rupture strain values (CFRP<1.5%; PET FRP>5%). Based on the test results, a beam-on-elastic foundation (BOEF) model is proposed for the buckling behavior of longitudinal reinforcing bars considering the lateral confining effect of FRP. Furthermore, based on the BOEF model and the test results, an empirical stress-strain model for steel rebar considering the buckling effect is developed. This model is then implemented into the OpenSees software platform and is validated through comparisons with compressive test results on cyclically loaded FRP-confined plain and RC columns. The complex mechanical interaction mechanisms among the FRP, buckling steel reinforcing bars, and the cover concrete are revealed and discussed. The proposed cyclic stress-strain model for laterally supported reinforcing bars is expected to serve as a fundamental model for predicting the seismic behaviour of FRP-strengthened RC columns.