Wind Load Cases 1 thru 4 (Fig. 27.3-8 in ASCE 7).
Wind Load Cases 1 thru 4 (Fig. 27.3-8 in ASCE 7).
(OP)
Hi,
I'm curious if people that are using the directional procedure for wind loading ever have Cases 2, 3, or 4 control. I'm usually doing residential, and I think these code provisions are there because of the design of the Citibank building in NYC. I solved the equation symbolically for a rectangular 2-story box and get a loading of 0.8625*P for one shear wall, and 0.6375 for the other (where P is the total load in Case 1). So Case 2 will never control, at least not for rectangular boxes with resistance elements on all sides.
Has anyone else come to the same conclusion?
I'm curious if people that are using the directional procedure for wind loading ever have Cases 2, 3, or 4 control. I'm usually doing residential, and I think these code provisions are there because of the design of the Citibank building in NYC. I solved the equation symbolically for a rectangular 2-story box and get a loading of 0.8625*P for one shear wall, and 0.6375 for the other (where P is the total load in Case 1). So Case 2 will never control, at least not for rectangular boxes with resistance elements on all sides.
Has anyone else come to the same conclusion?
RE: Wind Load Cases 1 thru 4 (Fig. 27.3-8 in ASCE 7).
RE: Wind Load Cases 1 thru 4 (Fig. 27.3-8 in ASCE 7).
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
RE: Wind Load Cases 1 thru 4 (Fig. 27.3-8 in ASCE 7).
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.