FRP约束混凝土圆柱有软化段时的应力-应变关系研究

试验研究了不同数量、不同类型(高强度、高弹模、高延性)FRP约束混凝土圆柱的应力-应变关系,发现其应力-应变关系曲线可能有软化段也可能没有软化段。指出FRP约束混凝土圆柱的轴向最大应力主要与侧向约束强度或侧向约束刚度有关,而轴向极限应变除了与该两个参数有关外,还与FRP的轴向极限拉应变有关。基于试验及搜集到的数据,提出判断FRP约束混凝土圆柱有无软化段的侧向约束强度与混凝土强度比界限值。基于对FRP侧向约束刚度和强度、FRP轴向极限拉应变、混凝土强度及弹性模量等参数的分析,提出了FRP约束混凝土圆柱有软化段时的峰值应力、峰值应变、极限应力及极限应变计算公式。最后,建议了两个确定FRP约束混凝土圆柱有软化段时的应力-应变关系模型。与大量试验数据的比较表明,本文建议的公式和模型与试验结果均符合较好。

Study of the stress-strain relationship of FRP-confined circular concrete column with a strain-softening response

The performances of circular concrete columns confined with FRP of various volumetric ratios and three different types of FRPs,including high strength FRP,high modulus of elasticity FRP and high ductility FRP,were tested.The FRP-confined circular concrete columns may or may not exhibit strain-softening.The maximum stress of FRP-confined concrete mainly depends on the confinement strength or the confinement modulus of FRP,while the axial ultimate strain of FRP-confined concrete is related not only to these two parameters but also to the ultimate tensile strain of FRP.Boundary values of the confinement ratio are suggested for determining the stress-strain curves of FRP-confined circular concrete columns with or without strain-softening.Based on the discussions on the effects of confinement strength and confinement modulus of FRP,the ultimate tensile strain of FRP,the strength and the modulus of elasticity of concrete,two stress-strain models as well as formulations for predicting the peak stress and the corresponding strain,the ultimate stress and the ultimate strain of FRP-confined circular concrete columns with strain-softening are proposed.The formulations and models demonstrate good agreement with experimental results from the present and previous studies.