土木工程专业英语 教学课件 陈瑛 4.3. Bond, Anchorage, and Development Length.pdfVIP

4.3 Bond, Anchorage, and Development Length 粘结、锚固、基本锚固长度 4.1 Fundamentals of Flexural Bond 无粘结梁Beam with unbonded interface between reinforcement and concrete If the reinforced concrete beam of Figure 4.17(a) was constructed using round reinforcing bars, and, furthermore, if those bars were greased or lubricated before the concrete were cast, the beam would be only little stronger than if it were built of plain concrete, without reinforcement. If a load were applied, as shown in Figure 4.17(b), the bars would tend to maintain their original length as the beam deflects. The bars would slip longitudinally with respect to the adjacent concrete, which would experience tensile strain due to flexure. For reinforced concrete, it is essential that bond forces be developed on the interface 界 面between concrete and steel, such as to prevent significant slip from occurring at that interface. Figure 4.17(c) shows the bond forces that act on the concrete at the interface as a result of bending, while Figure 4.17 (d) shows the equal and opposite bond forces acting on the reinforcement. It is through the action of these interface bond forces that the slip indicated in Figure 4.17 (b) is prevented. 钢筋与混凝土间具有足够的粘结是保证钢筋与混凝土共同受力变形的基本前提 粘结应力bond stress Some years ago, whenplain bars without surface deformations were used, initial bond strength was provided only by the relatively weak chemical adhesion and mechanical friction between steel and concrete 粘附力 有滑移时粘附力即消失 chemical adhesion chemical adhesion 钢筋受力较大时粘 摩擦力 结力主要由此二部 friction