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IBC 2012 All Heights Method

IBC 2012 All Heights Method

IBC 2012 All Heights Method

(OP)
IBC 2012 all heights method when calculating the wind load to the diaphragm are the windward and leeward loads considered together (summated) or separately?

RE: IBC 2012 All Heights Method

I assume you're referring to the alternate all-heights method?
I'm not completely familiar with this method but basically they use a factor which combines the external and internal pressure coefficient applied to the wall. You should apply both the windward and the leeward pressure at the same time. They are applied either toward or away from the wall based on positive or negative respectively. If the diaphragm is providing out of plane to the support at both the front and rear wall (as would be the case for a typical box structure) then yes these will both be loading the diaphragm as they are meant to be applied at the same time.

Hopefully that makes sense.

EIT
www.HowToEngineer.com

RE: IBC 2012 All Heights Method

(OP)
Yes the Alternate All heights method IBC 1609....I approached it with the windward and leeward values combined but I am troubled by the very high loads I am coming up with compared to the previous code which is why I questioned my method. It is a box type structure, three story with a parapet... and I am applying the wind loads perpendicular to the walls along with the parapet load....parapet load has a Cnet of 2.15 total windward and leeward which adds quite a bit of load to the roof diaphragm.

RE: IBC 2012 All Heights Method

In my opinion people overlook the parapet often when looking at MWFRS so good start there. Now in ASCE 7-10 they use a combined factor for windward and leeward pressures. They use +1.5 for the windward side parapet and -1.0 for the leeward parapet. So the combinded effect is 2.5. So it seems as though the IBC's factor is less. Unless they are apply the wind wardward and leeward factor to each parapet but that would give a factor of 4.3 which seems excessive.

Make sure you have properly factored the wind load (0.6 x WL) when using the strength level wind loads.

EIT
www.HowToEngineer.com

RE: IBC 2012 All Heights Method

(OP)
I included the .6 factor and include the parapet loading as you had described....still seems high so I am double checking my dimensions. Thanks

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