Wind Load Cases 1 thru 4 (Fig. 27.3-8 in ASCE 7).

For simply wood structures with flexible diaphragms? Pretty much. But if you get into rigid or semi-rigid diaphragms with odd shear wall layouts that require the resolution of torsion through the diaphragm with just a simple case 1, you can get some interesting results with the others.

Hi phamENG,

Yes, I should've included that. A simple wood structure with a flexible diaphragm. As I mentioned, I believe these load cases came from the design of the CitiTower in NYC, which has rigid diaphragms and no supports on the corners (or maybe no support on just one corner, it's been too long!). The building was found to be structurally deficient by a grad student studying the unique design. It was designed by only looking at Case 1 (before there was Cases 2, 3, or 4). Thanks for your confirmation.

On a similar note, I'm only seeing Case 3 to be relevant to hold down design, as two walls can share a common hold down. Would you agree?

Brad

I know quartering winds were the source of the problem with CitiTower, but I don't know if that caused the change in the building code or if a change in the building code prompted somebody to consider it - I don't know enough about the history of the code development to agree or argue with you.

Generally speaking, yes. Though the increase on the hold down is only about 6% for a square building which would be the worst case. That's usually not enough to make a difference, but might be if you're right on the line between hold downs.