Masonry C shaped Shear Wall Lateral Analysis 3

[crozroz0000]

Attached is a crude drawing of a c-shaped 8" reinf. CMU wall. 50' x 250' bldg 2 story. Roof Flexible, Floor rigid All thick walls may be shear walls.

I am looking for the shear per foot for the walls. I know there will be torsion introduced because of the C shape nature of the walls. I am thinking Torsion= Total lateral force at centroid of floor * distance from force to shear center of C-shaped wall.

Am I going the right direction to find shear load on each wall?

 

[DaveAtkins]

No, torsion is equal to total lateral force at centroid of floor times distance to center of rigidity. Center of rigidity is based on the length and location of all the shear walls.

DaveAtkins

 

[crozroz0000]

Thank you, Dave.

 

[shin25]

To make the calculation easier- why not neglect the flanged part of the shear walls in N-S direction?

 

[crozroz0000]

I was thinking about using all of the walls to find the center of rigidity. This way I could get correct Torsion due to lateral load in either direction. If I neglect them in my center of rigidity calculation, I think my torsions will be off. Am I thinking correctly?

 

[Grizzman]

you could let N-S walls take the direct shear and the E-W walls take the torsional shear.
Technically, neglecting the endwalls in your rigidity calc will increase your eccentricty. However the walls perpendicular to the lateral loads aren't generally designed to resist the lateral loads as this would make them beam columns versus shear walls.

 

[cldea8]

I haven't opened your file, however, remember that when you translate that moment (created from the diaphram force and center of rigidity) to the shear walls, you need to find the polar moment of inertia of all of the walls. (All of the shear walls in each direction will resist this moment)

Translating by using couple forces on the walls may be conservative in some instances...but not all

cldea8