Quartering winds

[bjb]

I heard someone talking about quartering winds, but unfortunately was not able to follow up. It's my understanding that in the case of a rectangular building, a quartering wind is one that is not orthogonal to either of the building axes. When is it appropriate to consider a quartering wind? Is it mostly a consideration if you have lateral resisting elements that that resist lateral loads applied to each orthogonal axis, like a corner column that has rigid connections for each axis?

 

[DaveAtkins]

I believe it is only an issue when lateral resisting elements (shear walls, braced frames, rigid frames) on two perpendicular walls meet at a corner. So I almost never worry about it. But if you are designing something like Citicorp Center in New York...

DaveAtkins

 

[WillisV]

Quartering winds are considered by the application of the load cases found in ASCE 7-98 Figure 6-9 as referenced by IBC 2000 for the main wind force resisting system. Note that the lods in Case 3 resolve to a force applied 45 degrees (quartering) to the main axis of the building. T

These load cases are required for all designs >60' and as of ASCE 7-02 for all buildings period - even if they are less than 60'.

 

[mrMikee]

bjb,

I brought up a related topic a few weeks ago in thread507-125928

My interest was that considering orthogonal seismic loads and wind loads per ASCE Figure 6-9 can result in many load combinations, the number of which depends of several factors. There were some interesting comments and I thought it was a good discussion.

These loads are important for columns that resist wind or seismic forces from both directions on a building. I've done a lot of work designing elevated bins where the height to width ratio is relatively large, and the effects quartering wind and orthogonal seismic loads are significant.

Regards,
-Mike

 

[bjb]

Thanks for the comments. Except for maybe one or two buildings that I have worked on, all my projects have been less than 60 feet high and I really haven't had to consider fig. 6-9 from ASCE 7-98. Here in New York State, our code is still based on the IBC 2000, so I haven't had the pleasure of dealing with ASCE 7-02. With the old New York State code, to get a wind pressure all you had to do was look it up in a table in the code. For most of the buildings that I work on, case 1 of fig. 6-9 would probably govern.