（双语版）混凝土结构设计原理课件.ppt

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1、Concrete Structural Fundamentals,混凝土结构基本原理,主 讲：管 巧 艳,2010-10-11,CHARPTRE 5 SHEAR STRENGTH OF MEMBERS(构件的受剪承载力),5.1 Introduction(概述),受弯构件(a member under flexure)除承受弯矩(moment)外，往往还同时承受剪力(shear)。即使构件配置有足够的纵筋(longitudinal reinforcement)以抵抗正截面(perpendicular sections)的弯矩，构件仍有可能发生破坏，这是因为在弯矩和剪力的共同作用下斜截面(dia

2、gonal sections)强度不足引起的.,斜截面破坏带有脆性破坏的性质，缺乏明显的预兆，设计人员必须使设计的构件既能抵抗弯矩，也能抵抗剪力,For this purpose,transverse reinforcement(横向钢筋）,or the so called web reinforcement（腹筋）,must be designed to provide adequate ultimate strength for the diagonal sections.The web reinforcement may be composed of transverse ties or

3、 stirrups（箍筋）and inclined bars（斜筋）bent up from the surplus longitudinal reinforcing bars.,5.2 The Mechanism of Shear Resistance in Reinforced Concrete Beams without Web Reinforcement（无腹筋钢筋混凝土梁的受剪机理）,5.2.1 Stress State of Reinforced Concrete Beams without Web Reinforcement before Diagonal Cracks（无腹筋梁

4、斜裂缝出现前的应力状态）,The normal stress and shear stress at any point in a cross section E-E of the beam can be expressed as,The principal tension stress and the principal compression stress can be expressed as,主拉应力的作用方向与梁纵轴的夹角,单元2位于中和轴处，该单元上只作用有剪应力(shear stress)，而无正应力(direct stress)，主拉应力与主压应力相互垂直与梁轴线成450角，主

5、拉应力与主压应力的大小相等，均等于剪应力,分析图5.2有：,单元1在梁受压区内，单元作用有剪应力和压应力，由于压应力的存在，使得主拉应力小于主压应力，且主拉应力与梁轴线的夹角大于450,单元3在梁受拉区内，单元上作用有剪应力和拉应力，由于拉应力的存在，使得主拉应力大于主压应力，且主拉应力与梁轴线的夹角小于450,5.2.2 Stress State of Reinforced Concrete Beams without Web Reinforcement after Diagonal Cracks（无腹筋梁斜裂缝出现后的应力状态）,When the principal tensile str

6、ess exceeds the tensile strength of concrete,cracking is produced in a reinforced concrete beam,and the cracks are formed perpendicularly to the tensile stress trajectories.,In the regions of large bending moments,cracks develop almost perpendicularly to the axis of the beam.These cracks are called“flexural cracks”.（弯曲裂缝）,In regions of high shear due to the diagonal tension,the inclined cracks developed as an extension of the flexural cracks and are termed“flexural-shear cracks”.（弯剪裂缝）,Some diag