Shear Wall Overturning
Shear Wall Overturning
(OP)
Good Morning/Afternoon All,
Looking for a little clarification on ASCE 7-05 Section 6.4.2.1.1 Minimum Pressures. In that section it says that all pressures in Zones A, B, C, and D should be +10psf while Zones E, F, G, and H should all be 0psf. This is where my question comes in. If my Zone B pressure calcs out to be 5 psf should I then use 10 psf as a minimum design for overturning of a shear wall and set uplift pressures equal to zero? (Case 2 in attachment) It seems highly unconservative to neglect uplift forces for overturning of shear walls. Or is the correct procedure to use the calculated value of 5 psf + Zone C + Net Uplift for overturning and the minimum 10 psf + Zone C when determining shear only forces. I have attached an arbitrary interior shear wall for review.
Thanks much!
Looking for a little clarification on ASCE 7-05 Section 6.4.2.1.1 Minimum Pressures. In that section it says that all pressures in Zones A, B, C, and D should be +10psf while Zones E, F, G, and H should all be 0psf. This is where my question comes in. If my Zone B pressure calcs out to be 5 psf should I then use 10 psf as a minimum design for overturning of a shear wall and set uplift pressures equal to zero? (Case 2 in attachment) It seems highly unconservative to neglect uplift forces for overturning of shear walls. Or is the correct procedure to use the calculated value of 5 psf + Zone C + Net Uplift for overturning and the minimum 10 psf + Zone C when determining shear only forces. I have attached an arbitrary interior shear wall for review.
Thanks much!






RE: Shear Wall Overturning
This means that any force, moment, shear, etc. found from your straight-up load case (your 5 psf example) must not be smaller than that found using the 10 psf projected area approach.
You are comparing individual shears, moments, etc (i.e. effects) rather than global forces.
RE: Shear Wall Overturning
If the two loads oppose each other treat the roof component as zero, if they are additive (steep roof slope) than add the A & B zones (or C & D) together.
Check Note 7 on Figure 6-2