FRP约束高温（火灾）后混凝土轴压力学性能与破坏机理研究

Fiber-reinforced polymer (FRP) is often used to strengthen fire-damaged RC columns. However, the lack of understanding on the structural behavior of fire-damaged concrete columns confined with fiber-reinforced polymer wraps hinders the applications of FRP in practice.. This project aims to investigate the axial compressive properties and failure mechanism of fire-damaged concrete columns confined with FRP wraps through systemic compressive tests on FRP-confined concrete columns with/without fire (or heat) damage. The project includes four parts: (1) tests will be conducted to investigate the effects of various parameters on the effective tensile strain of FRP wraps; (2) compressive peak stress and peak strain models of fire-damaged concrete confined with FRP wraps will be established based upon the existing experimental results and models (i.e., without fire damage); (3) an analytical stress-strain model will be developed through increment iteration method for FRP-confined various fire-damaged concrete columns on the basis of independent stress path assumption; and (4) a finite element model will be developed to predict the structural behavior and failure mechanism of FRP-confined fire-damaged concrete columns based on a modified concrete damaged plasticity model with the consideration of fire damage and confinement effects, and a parametric study will be carried out to investigate the influences of different design parameters and to generate simplified design guidelines.. The project outcomes are expected to be theoretical basis and design reference for practical use of FRP wraps in strengthening fire-damaged concrete columns. Thus it is valuable for both scientific research and engineering practice.

钢筋混凝土柱经常面临火灾后采用FRP进行修复和加固的问题。但目前FRP约束高温损伤后混凝土轴压力学性能方面的理论研究滞后于工程应用。本项目通过FRP约束未损伤和高温损伤后混凝土试件轴压试验，系统研究FRP约束高温损伤后混凝土轴压力学性能与破坏机理。具体研究计划如下：(1)基于不同试验工况，研究多因素影响下FRP有效极限拉应变；(2)基于试验数据和已有模型，建立FRP约束高温损伤后混凝土轴压峰值应力和峰值应变计算模型；(3)基于应力路径无关假定，运用增量迭代法计算得到FRP约束高温损伤后混凝土轴压分析型应力-应变模型；(4)考虑温度历史和约束效应，修正现有混凝土塑性损伤模型，建立FRP约束高温（火灾）后钢筋混凝土柱轴压有限元模型，通过试验验证和数值扩展试验，提出简化设计方法。本项目成果可作为FRP约束高温损伤后混凝土柱轴压力学性能的研究基础和设计依据，因而具有重要的科研意义和工程应用价值。

钢筋混凝土柱经常面临火灾后采用FRP进行修复和加固的问题。但目前FRP约束高温损伤后混凝土轴压力学性能方面的理论研究滞后于工程应用。本项目通过FRP约束未损伤和高温损伤后混凝土试件轴压试验，系统研究FRP约束高温损伤后混凝土轴压力学性能与破坏机理。具体完成的研究内容为：(1)基于轴向拉伸试验、裂盘试验和实际约束混凝土试验和近20年材性试验数据，得到了裂盘试验和轴向拉伸试验FRP极限拉应变比值与弹性模量之间的关系式，建议了实际工程中FRP材性试验方法和FRP约束高温损伤混凝土时FRP有效极限拉应变计算模型；(2)对102个未损伤和高温损伤后的圆柱和方柱进行了FRP约束后的轴压性能试验，发现采用典型的FRP约束常温未损伤混凝土轴压强度和变形计算模型预测FRP约束高温损伤混凝土轴压极限强度和极限变形时存在较大的偏差。通过构建柱状膜结构静水压力平衡模型和约束混凝土方柱与FRP体积应变能平衡模型，并基于本文试验数据，确定了FRP约束高温损伤混凝土应力和应变计算模型中与温度相关的参量，建议了适用于预测FRP约束高温损伤混凝土的极限应力计算模型和极限应变计算模型；(3) 对14根损伤后未加固和FRP约束加固的钢筋混凝土柱进行轴压性能试验，对试件受火过程中的温度场进行了数值模拟，模拟结果与实测结果吻合较好，得到了柱轴向荷载-位移曲线、轴向荷载-横向应变曲线及不同温度损伤、保护层厚度、FRP层数对约束损伤柱轴压承载力和变形的影响规律。