《混凝土结构设计原理》双语 (7).ppt

Chapter 7 Shear Resistance 7.1 Shear Failure of RC Beams without Shear Reinforcement 7.1.1 Shear in homogeneous beams and in RC beams Crack vs flexural and shear stresses for a RC beam Crack patterns follow the principal compressive stress paths Stresses in different segments 7.1.2 Types of shear failure The type of shear failure of RC beams depends mainly on various factors: One of the most significant factors is the shear-span/depth ratio , Shear span av is defined as the distance between points of zero and maximum moments. Category I ( ): Deep beam failure 2. Category II: Shear-compression failure Dowel（销拴） failure 3. Category III ( 4. Category IV ( ): Flexural failure 7.1.3 Mechanisms of shear transfer of RC Beams without Shear Reinforcement Consider a typical beam in bending and shear shown below, which is reinforced with longitudinal steel against bending. The shear force is transmitted through the cracked beam by a combination of three mechanisms (Fig. 7.1-6) The external shear force V is resisted by the combined action of Vc, Va and Vd . Equilibrium condition 7.2 Shear Failure of RC Beams with Shear Reinforcement The complementary shear stress gives rise to diagonal tension and compressive stresses. Concrete is weak in tension, and shear failure is then caused by a failure in diagonal tension with cracks running at about 45?. Shear reinforcement should be provided by bars that cross the cracks. Theoretically, either vertical links (stirrups) or inclined bars will serve this purpose. 7.2.1 Types of shear reinforcement in beams Links or vertical stirrups （箍筋） 7.2.2 Contribution of shear reinforcement  (web reinforcement) 7.2.3 Influence of shear reinforcement on failure modes 7.3 The shear capacity is strongly dependant on , and is also affected by:  Location of load on cross section Reinforcement ratio % 7.4 Truss analogy ( The