FRP约束混凝土圆柱应力-应变模型的适用性

Applicability of stress-strain model for FRP-confined concrete cylinders

纤维增强复合材料(FRP)约束混凝土的应力-应变模型分为设计型模型和分析型模型.设计型模型通过对实验数据的回归分析给出数学公式显式表达轴向应力-应变关系.分析型模型则基于混凝土的轴向应力-应变关系与应力路径无关的假设,通过增量法获取FRP约束混凝土的轴向应力-应变曲线.为有助于在结构分析中合理选取模型,对以FRP约束混凝土圆柱为研究对象的2种模型的发展和特点进行综述;通过分析设计型模型的控制变量围压比与分析型模型的轴向应力的应力路径相关性,研究各模型的适用性.对于设计型模型,由于施工工艺、产品材料以及测量方法的差异引起的围压比的不确定性是影响其适用性的主要因素;对于分析型模型,应力路径相关性是影响其适用范围的主要原因.分析结果表明:当主动约束与被动约束达到相同值时的轴向应力比不为1,该应力比与侧向约束刚度比呈线性反比关系.在现有的分析型模型中引入轴向应力比是扩大该类模型适用范围的关键.

The stress-strain models of fiber reinforced plastic-confined （FRP-confined） concrete are classified into, design-oriented models and analysis-oriented models. The design-oriented models use mathematical formulas regressed by test data to describe the stress-strain behavior explicitly. The analysis- oriented models are based on the assumption that the path is independence on the stress-strain relationship, and obtain the axial stress-strain curves of FRP-confined concrete through incremental method. A state-of- art review was conducted on the development and features of two models for FRP-confined concrete cylinders in order to assist the model selection in the structural analysis. And the applicability of each model was investigated by analyzing the lateral confinement ratio of controlling variable for the design- oriented models and the path-dependence of axial stress for the analysis-oriented models. For the former models, the uncertainty of lateral confinement ratio caused by the variation in workmanship, products or measurement method is the key factor affecting the applicability. For the latter ones, the path dependence has been proved to be the key factor limiting the application scope. The analysis results demonstrate that the axial stress ratio doesn＇t equal one when the active confinement and the passive confinement reach the same pressure. The axial stress ratio is in inverse proportion to the lateral confinement stiffness ratio. It is essential to introduce the axial stress ratio into the existing analysis-oriented model to extend the application scope.