Wind design - ommiting end conditions.

[stillfan]

I have been going through some calculation sets where I have found in the longitudinal direction wind design the end condition values were overlooked. Is there a resonable explaination for ommiting these values on a MWFR building.

One explanation the engineer offered is that the building is flexible and the loads are being distributed in that manner.

The building has a frequency higher than 1 so the design is based on a ridgid structure, even at that if they did design it for a flexible building the end zones should not be ignored.

The calculations originated in Europe so perhaps the European code does not account for the End zones?

 

[slickdeals]

Corner pressures (End Zones 5) are typically accounted only in component and cladding design. For MWFRS, corner pressures are not applied.

 

[ron9876]

In ASCE7 corner zones should be used for MWFRS loads.

 

[OldPaperMaker]

Stillfan,
I think that the answer depends on which ASCE7 Method you are using.
For Method 1 there are clearly different end zones for the roof & walls.
For Method 2, All-Heights there no end zones for windward, leeward & side wall but there are different Cp values for the roofs in the bottom part of Figure 6-6 on page 49.
Method 2, Low-rise Walls & Roofs (Figure 6-10)has all sorts of zones.

The Structural Engineers Association of Washington & Applied Technology Council has a series of books, SEAW/ATC 60 that compares the 3 methods and concludes that a all methods yield similar results. The big difference is that the Low-rise Walls & Roof method requires a lot of bookkeeping to get to the actual results.

 

[ron9876]

I was wrong. oldpapermaker has it.

 

[JedClampett]

I sometimes don't use them for my wall design, since the walls are designed vertically and these zones have the corners to distribute the loads in another direction. Other times, I just design the whole wall for the zone 5 loads to be conservative.
But they do come into play for architectural and HVAC items such as louvers, doors and windows. And these have small effective wind areas, which have the highest loads. Technically, per IBC Chapter 16, you're supposed to post the wind loads by zones on the drawings for walls and roofs.

 

[rscassar]

Does the long direction wind design look at the wind forces on the entire structure? Local pressures are only applicable to the design of cladding or the members which immediatley support the cladding.