高温环境下GFRP植筋与混凝土界面粘结行为分析

Analysis of Interfacial Bond Behavior Between ETS GFRP Bars and Concrete Under High Temperature

摘要:

为探究高温环境对玻璃纤维增强复合材料(GFRP)筋-混凝土界面粘结性能的劣化机理,基于纤维聚合物复合材料(FRP)植筋技术,设计并制备了108个拉拔试件,开展了界面粘结性能试验,试验变量包含温度(20、40、60、80、120、160 ℃)、混凝土强度等级(C30、C40、C50)及GFRP筋直径(8、12、16 mm)等关键参数。试验表明:当温度达到粘结剂玻璃化温度T_g时,试件破坏模式发生显著转变,由混凝土基体劈裂破坏转变为界面剥离破坏;在界面剥离破坏模式下,典型粘结-滑移曲线可划分为线性上升段、软化段和残余强度段3个特征阶段。基于断裂力学理论和试验数据回归分析,建立了粘结强度、残余粘结强度及断裂能与温度参数相关性的计算模型。研究表明:温度升高对界面粘结性能具有显著劣化效应,尤其在接近粘结剂玻璃化温度T_g时,粘结强度呈指数级下降。与试验数据对比验证,本模型预测误差在10%以内,具有较高的工程适用性。

Abstract:

To explore the deterioration mechanism of the bonding performance of Embedded Through-Section (ETS) Glass Fiber Reinforced Plastic (GFRP) bar-concrete interface in high-temperature environments, and based on the Fiber Reinforced Polymer (FRP) bar technology, 108 pull-out specimens were designed and prepared in this study. The test variables included three key parameters: temperature (20,40,60,80,120 and 160 ℃), concrete strength grade (C30, C40 and C50) and GFRP bar diameter (8, 12 and 16 mm). The test showed that when the temperature reached the glass transition temperature (T_g) of the adhesive, the failure mode of the specimens changed significantly, and the splitting failure of the concrete matrix evolved into interfacial debonding failure. Under the interfacial debonding failure mode, the typical bond-slip curve could be divided into three characteristic stages: linear rising stage, softening stage and residual strength stage. Based on the theory of fracture mechanics and the regression analysis of experimental data, a calculation model of the correlations of bond strength, residual bond strength and fracture energy with temperature parameters was established. The results showed that the increase of temperature had a significant deteriorating effect on the interfacial bonding performance, especially when it was close to the adhesive's T_g, the bond strength showed an exponential decay trend. Compared with the experimental data, the prediction error of this model was within 10%, and the model has high engineering applicability.