光圆钢筋与混凝土界面粘结滑移本构模型研究

Bond-Slip Constitutive Model of the Interface Between Plain Bar and Concrete

对配置光圆钢筋的既有混凝土结构进行承载性能评估时,钢筋与混凝土界面粘结性能优劣是评价该类混凝土结构的重要内容。为此,制作了4组光圆钢筋的中心拉拔试件和2组变形钢筋对比试件,选取粘结长度、钢筋表面形式为主要变量对粘结性能进行试验研究,并通过4组铝合金拉拔试件对比分析光圆筋与混凝土界面的粘结机理。研究结果表明:光圆钢筋的粘结强度显著小于变形钢筋的粘结强度,平均约为变形钢筋粘结强度的18.3%;光圆钢筋的粘结强度主要由化学粘着力和界面摩擦力构成,而铝合金的粘结强度则由化学粘着力构成,平均约为光圆钢筋粘结强度的10%;增加粘结长度后,光圆钢筋的粘结强度随之增大,但铝合金筋的粘结强度无明显变化。进一步基于试验结果及理论分析,建立了光圆钢筋与混凝土界面的粘结-滑移本构模型,并通过已有试验数据对建议模型进行了验证,吻合较好。

When evaluating the performance of existing concrete structures reinforced with plain bars,the bond behavior between the reinforcing bar and surrounding concrete is a vital topic of these historical concrete buildings. A total of four groups pullout specimens with plain steel bars and two group specimens with deformed steel bars,serving as a reference,were experimentally investigated and presented in this study. The main test parameters included embedment length,and surface type of reinforcing bars. The bond mechanism of plain steel reinforcing bars against the surrounding concrete was analyzed by comparing with four groups pullout specimens with aluminium alloy bars. The results indicate that the bond stress experienced by plain bars is quit lower than that of deformed bars. Averagely,plain bars appeare to develop only 18. 3% of the bond stress of deformed bars. Differing from the bond strength of plain steel bars,which is based primarily on chemical adhesion and friction force,the bond stress of aluminium alloy bars is mainly experienced by chemical adhesion,which is just 10% of that of plain steel bars. The bond stress of plain bars increase when increasing the embedment length. However,the bond stress of aluminium alloy bars is not affected by the embedment length. Based on the test results and theoretical analysis,the bond-slip model at the interface between concrete and plain bars is put forward.Good agreement is achieved between the test curves and the predicted curves at both the loaded and free ends.