玄武岩纤维布约束高温损伤混凝土方柱轴压力学性能试验

对36个玄武岩纤维布增强聚合物基复合材料（BFRP）约束的高温损伤混凝土方柱和15个不同高温损伤的对比试件进行了轴压试验。试验表明，玄武岩纤维布横向约束能改变高温损伤后混凝土方柱的破坏形态，显著提高混凝土方柱的轴压强度和变形能力。其中三层玄武岩纤维布包裹的200℃、400℃、600℃和800℃高温损伤混凝土方柱轴压强度分别提高了48%、130%、206%和389%，轴向变形分别提高了433%、344%、319%和251%。采用典型的纤维增强聚合物基复合材料（FRP）约束常温未损伤混凝土轴压力学性能的设计模型预测FRP约束高温损伤混凝土的轴压强度和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，分别改进了FRP约束混凝土方柱轴压极限应力和极限应变计算模型的基本形式。基于该基本形式和试验数据，分别确定了BFRP约束高温损伤混凝土方柱轴压极限应力和极限应变计算中与温度相关的参量，提出了适用于高温损伤混凝土方柱的轴压极限应力和极限应变的设计模型。 

Axial compressive behavior of post-heated square concrete columns wrapped by BFRP sheets: An experimental investigation

This paper presents an experimental study on the axial compressive behavior of 36 heat-damaged square columns wrapped by basalt fiber-reinforced polymer (BFRP) sheets and 15 reference columns after different levels of heat damage. The test results indicate that the BFRP confinement can change the failure mode of heat-damaged square columns and significantly enhance the strength and deformation properties of these columns. For the heat-damaged columns wrapped with three layers of BFRP sheets, the axial strengths of these columns after exposuring to 200℃, 400℃, 600℃ and 800℃ are increased by 48%, 130%, 206% and 389%, respectively; and the corresponding axial deformation increases are 433%, 344%, 319% and 251%, respectively. The typical ultimate stress and ultimate strain models for fiber-reinforced polymer (FRP)-confined undamaged concrete are not suitable for FRP-confined heat-damaged concrete. Through establishing the hydrostatic pressure balance equation of the cylindrical FRP membrane as well as proposing the volumetric strain energy models of confined concrete and BFRP sheets, the basic formulas defined for the axial ultimate stress and axial ultimate strain of FRP confined fire-damaged concrete columns are modified. The temperature-dependent variables in the proposed formulas were determined based on the presented experimental results, and therefore, design-oriented models were established for axial ultimate stress and axial ultimate strain of FRP-confined heat-damaged square concrete columns.