钢筋混凝土构件设计中两个问题的商榷

钢筋混凝土基本构件设计中,有两个问题值得商榷:(1)双筋受弯构件、大偏心受拉构件以及大偏心受压构件的正截面设计问题中的常见做法是在基于截面等效受压区高度等于界限高度时截面纵筋总配筋量最少的认识下将截面设计成界限截面,但根据推导,界限截面并不是纵筋总配筋量最少的条件,而且设计成界限截面还会丧失截面的延性,降低构件的可靠度.(2)在受弯构件斜截面抗剪承载力计算中,由于规范没有给出简化斜截面的水平投影范围,导致许多设计师无法计算斜截面上的剪力,继而用斜截面始端对应的正截面上的剪力值代替斜截面上的剪力值,这在概念上是矛盾的;同时,在有分布荷载作用时,数值上也是夸大的.

On Two Questions in R.C. Member Design

There are two misconceptions in the design of reinforced concrete members.On the normal section design of doubly reinforced flexural members,tension members with large eccentricity and compression members with large eccentricity,the balanced section is designed in general,of which the equifinal depth of compression zone equals to the balanced depth of compression zone.It's believed that balanced sections may consume the least total longitudinal reinforcing bars.Whereas,by deriving,the total longitudinal reinforcing bars of balanced sections are not least;Moreover,the ductility and reliability is reduced in balanced sections.On the shear strength design of flexural members,the shear force in cross section corresponded to the initial point of oblique section is used to substitute the oblique section's shear force by many designers.This is wrong in concept and magnifies the value of oblique section's shear force in the case of distributive loads is applied.