d = 0.8Lw for Shear Forces in a Wall

[plopez]

Hi, I don't understand why tha ACI Code takes the value of
d= 0.8Lw to evaluate the Shear forces in a RC wall.
(See Code ACI 318-95 Chap.11.10.4)
In a wall with Lw=5,0 mts. you cannot loose 1,0 mt of wall capacity to resist the shear forces.

Can someone tell me the reason of this?

 

[DaveAtkins]

Shear walls behave like deep beams, which means the traditional linear strain seen in typical beams is not applicable. The "d" distance for a deep beam or a shear wall is more accurately 0.8 times the depth of the beam or the length of the wall, and the remaining portion of the beam or wall cannot resist shear. DaveAtkins