ASCE 7-05 SIMPLIFIED METHOD - WALL PRESSURES

[CONEJO]

Hi gurus - I recently had someone argue that since the wall pressures in ACE 7-05 Method 1 tables are the sum of windward and leeward pressures (given the commentary saying that because of the diaphragms internal pressures cancel out), the pressures for wall design would be split in two because they would be "shared" by the two walls, with windward and leeward walls each carrying half of the pressure. This is argued from the standpoint of the building diagrams that show pressure only on the windward wall, and not on the leeward wall for wind blowing along the ridge. I disagree, because if one looks at Method 2, the walls don't know which method was used to design them, and it is clear from Method 2 that both of them have loading.

Also, some of the pressures listed are less than 10PSF, which is the minimum pressure that can be applied for analysis. Should the pressures on the tables for Method 1 be increased to 10 PSF? Any information will be greatly appreciated.

 

[MiketheEngineer]

On small buildings, I use a minimum of 10 psf to check each wall and the add the pressures to do a whole building analysis. That is my simplified method.

Also check corners, overhangs, etc...

 

[ron9876]

The combined wall pressures are MWFRS loads.

 

[TXStructural]

You say "for wall design", but the main wind force-resisting system (MWFRS) is for design of lateral elements, not walls receiving direct wind. The design of walls receiving direct wind should be designed for component and cladding loads (C&C), which will be higher.

As for minimums, the values on Fig 6-2 must be adjusted using the equation in 6.4.2.1 or 6.4.2.2, AND THEN the 10 psf minimums would apply. That's why values lower than 10 psf appear in the figures. Also, the 10 psf is check against mistakes, since it requires that you simply take the (essentially rectangular) profile of the building and apply a minimum of 10 psf.

 

[asixth]

If it is an external wall it needs to be designed for the highest possibly wind pressure that wall can be subjected to. The combination that I immediately think of is sidewall suction pressures from external loads and positive internal pressure from an opening created somewhere along the windward face. I did condition assessments early this year following one of the strongest cyclones (hurricanes) in Australian recorded history and I saw many sidewall blowouts.