ChickenBake
Structural
I am trying to wrap my head around the "reduction factor" provided in ASCE 7-16 12.11.2.1 because it appears to be that the way the code is written makes this factor literally impossible to apply.
Equation 12.11-1 calculates the force for out-of-plane wall anchorage as Fp = 0.4*Sds*ka*Ie*Wp. The ka factor may be taken as unity for rigid diaphragms, so for those cases we can reduce the equation to Fp = 0.4*Sds*Ie*Wp.
The section then goes on to state that if you are designing anchors for a wall for a case where all diaphragms in the building are rigid, you may reduce this force by (1+2*z/h)/3. So far, so good right?
Except the code goes on to say that your reduced force cannot be less than what you'd calculate in section 12.11.1 - design forces for the wall design. The equation given in that section is Fp = 0.4*Sds*Ie*Wp. This is, quite literally, the exact same equation as the one used for wall anchors at rigid diapgragms.
It seems to me that by definition there are literally zero cases where the exception applies, which begs the question, why is it provided in the first place? Can anyone shed some light on where I might be going wrong?
Equation 12.11-1 calculates the force for out-of-plane wall anchorage as Fp = 0.4*Sds*ka*Ie*Wp. The ka factor may be taken as unity for rigid diaphragms, so for those cases we can reduce the equation to Fp = 0.4*Sds*Ie*Wp.
The section then goes on to state that if you are designing anchors for a wall for a case where all diaphragms in the building are rigid, you may reduce this force by (1+2*z/h)/3. So far, so good right?
Except the code goes on to say that your reduced force cannot be less than what you'd calculate in section 12.11.1 - design forces for the wall design. The equation given in that section is Fp = 0.4*Sds*Ie*Wp. This is, quite literally, the exact same equation as the one used for wall anchors at rigid diapgragms.
It seems to me that by definition there are literally zero cases where the exception applies, which begs the question, why is it provided in the first place? Can anyone shed some light on where I might be going wrong?
