混凝土设计基本原理第章受扭构件的扭曲截面承载力.ppt

扭剪型破坏 扭型破坏 弯型破坏 2、满足下列条件可按构造配置剪扭钢筋： 3、出现下列情况时，可不考虑剪力或扭矩的作用 (1)当 (2) 当 可不考虑剪力，即V＝0 可不考虑扭矩，即T＝0 1、截面尺寸验算 二者中的较大值 4、最小配筋率 When ? is from 0.333 to 3 ，all torsional reinforcements can yield at ultimate torsion moment. Chinese Code: ? =0.6-1.7 ?--Ratio of strength of longitudinal bars to stirrups 240 240 1300 第7章 受扭构件承载力计算 Chaper 7 Torsional strength of members 7.1 （概述）Introduction 7.2（纯扭构件试验研究） Experiment about pure torsion member 7.3 （纯扭构件承载力）Torsional capacity of members under pure torsion 7.4 （弯、剪、扭构件承载力）Torsional capacity of member under combined flexure, shear and torsion 7.7（构造要求） Detailing requirements 7.1 Introduction（概述） 两类扭矩（Two types of torsion） Equilibrium torsion (平衡扭矩)：根据静力平衡条件确定的扭矩、初始扭矩 statically determinate torsion; primary torsion 由静力平衡确定，与刚度无关 It is determined based on static equilibrium, and not related to the torsional stiffness. Compatibility torsion (协调扭矩)： statically indeterminate torsion（超静定扭矩）; secondary torsion 无法根据静力平衡确定，与刚度及变形相关 It cannot be determined based on static equilibrium alone, and related to the torsional stiffness and deformation of members . 7.2 Experiment of pure torsion 1.（开裂前纯扭构件受力分析） Mechanical analysis of pure torsion before crack 主拉应力超过抗拉强度后，开裂，并沿45 °斜向发展，和上下底面相交后进行发展，形成螺旋形斜裂缝，构件破坏。 When the principle stresses exceed the tensile strength, cracks form at the middle point of longer side and extend diagonally along 45°line to the neighboring faces. Finally, cracks are spiral when the member reaches its ultimate capacity. Spiral cracks 2. Torsional reinforcements（受扭钢筋） Stirrups Longitudinal bars 2. 受扭破坏模式 scarce-reinforced failure（少筋破坏） Tension failure Under-reinforced failure（适筋破坏） Bending failure Under-reinforced member , scarce-reinforced member , Partially over-reinforced member , Over-reinforced member When member is adequately reinforced , the reinforcements yield before concrete crushes. Calculation of torsional strength（承载力计算） When torsional reinforcements are inadequate , members fail as soon as cracks form. Minimum a