FRP约束混凝土强弱约束判断准则

基于数值模拟和以往研究,分析了不同强弱约束状态下的FRP约束混凝土行为.分析结果表明:(1)约束混凝土应力-应变曲线根据强弱约束状态不同而发生变化,处于强约束条件下的混凝土,极限强度大于无约束混凝土强度,对于加固量较小的弱约束混凝土,破坏时的应力值等于或者小于无约束混凝土的强度;(2)计算非圆形截面的约束应力、约束刚度、极限约束应力时要考虑形状等效系数kse,约束混凝土极限状态下的FRP断裂应变小于FRP极限拉应变,对于混凝土圆柱,FRP断裂应变可等效为环形劈裂试验值,对于非圆形截面,需计入形状等效系数kse的影响;(3)定义极限约束应力与无约束混凝土强度比值为约束比,约束比决定混凝土强弱约束状态.通过对收集到的试验数据进行回归,提出了强弱约束判断准则.

Criteria of Powerful or Weak Confinement for FRP-confined Concrete

Based on the numerical simulation and related studies,the behavior of FRP-confined concrete under powerful confinement and weak confinement is analyzed in this paper.The results show that:(1) The stress-strain curve is different according to the confinement condition whether is powerful or not.For the powerful confinement,the stress-strain curve is ascending straight line in the second stage,but it's contrary to the weak confinement confined concrete.(2) For the non-circular section,the equivalent section coefficient kse should be considered when calculate restraint stress,restraint stiffness and ultimate restraint stress.The rupture strain of FRP-confined concrete in ultimate status is less than that from flat coupon tensile test.For the confined concrete cylinder,the rupture strain of FRP can be equivalent to the value of the ring splitting test,but to the non-circular section,the influence of section shape should be considered.(3) The confinement ratio is defined as the ratio of ultimate restraint stress to concrete strength under the unconfinement condition,which is used to determine confinement condition.The criteria of powerful or weak confinement is proposed through the regression for collection test data.