求取内嵌FRP加固混凝土梁界面滑移量的一种新方法

A new innovation of research on the interface slip of concrete beam strengthened with near-surface mounted fiber reinforced plastics bars

FRP筋与混凝土之间界面的粘结性能是FRP筋混凝土结构中最关键的力学特性,要准确预测FRP-混凝土的剥离破坏,必须确定合适的黏结滑移关系。为建立相对准确的界面粘结滑移模型,在提出内嵌CFRP筋加固混凝土梁界面特性研究新的试验方法的基础上,开展了11根混凝土梁的四点弯试验。借助岩石中树脂锚杆与锚固剂界面的剪应力模型,导出了CFRP筋横断面上轴向正应力沿CFRP筋锚固长度分布的解析式,进而得到CFRP筋锚固段的伸长量,结合试验获得的CFRP筋指定截面测定的滑移量、外露CFRP筋的伸长量,最后得到了CFRP筋与混凝土界面的滑移量,绘制了CFRP筋-混凝土界面的粘结-滑移曲线。试验和分析计算表明,新构建的CFRP筋与混凝土界面滑移量的求取方法,混凝土-CFRP筋界面的滑移量及粘结-滑移曲线准确简单,省去了在CFRP筋上密贴应变片的麻烦,排除了应变片对界面受力的干扰,对CFRP筋-混凝土界面的特性研究具有示范指导作用。

Bonding performance of the interface between FRP bars and concrete is the key of mechanics properties in the concrete structure strengthened with FRP bars, the constitutive relations of the interface bonding performance is described by the interface bond-slip modle of FRP-concrete, which predict the stripping damage of FRP-concrete and must determine the appropriate bond-slip model. In order to establish an interface bond-slip modle, a four-point bending test of 11 concrete beams was carried out on the basis of a new test method to study the interface characteristics of reinforced concrete beams with embedded CFRP bars. Based on the shear stress model of the interface between resin bolt and anchoring agent in rock, the analytical expression of the axial normal stress of CFRP bar along the anchorage length of CFRP bar in the cross-section is derived, and the elongation of CFRP bar anchorage segment is obtained. In combination with the measured slip of the specified section of CFRP bar and the elongation of exposed CFRP bar, the slip of the interface between CFRP bar and concrete is obtained, and the bond-slip curve of the interface between CFRP bar and concrete is plotted.Test and analysis calculation to the wide-notch beam show that the bonding shear stress and the slip properties is easy to obtain by using the testing system, and design section slip and easy to measure, bars stress is clear and the average interface shear stress of the CFRP is convenient to obtain, the slip and binding-slip curve is accurate and simple, the interference of strain gauge is eliminated , so it has demonstrative guidance to the research on the interface properties of CFRP-Concrete.