Friday, September 30, 2011

RE: Wind forces on the columns of open structure

All 4 columns should be loaded.  Pipe racks and open industrial structures are similar.  You can not use shielding from an adjacent element.  The air flow reforms so close to the windward element that you can not achieve shielding on the leeward element.  The only way to compute shielding is to use a computational fluid dynamics model or a wind tunnel test.  And then you find that you should have applied the wind on all 4 columns and wasted a lot of time. 

Regards, Harold Sprague

Date: Fri, 30 Sep 2011 10:16:10 -0700
Subject: Wind forces on the columns of open structure

I tried to send a message yesterday on this subject. But with new phones, new wireless providers, a move across country etc i'm not sure it went through.
Anyway I am designing an outdoor picnic pavilion.  The plan dimensions are about 60' x 30'. It will have monoslope roof supported by 4 bays of 3 columns. I have calculated the wind loads for the MWFRS at the roof.  I can't decide on what ASCE requirements/equations to use for the MWFRS loads to the columns and if that load should be applied to each column in each row parallel to the load direction.  In another words if there are 4 columns in line parallel to the wind load would all 4 columns be loaded?
I have considered using loads calculated from section 6.5.15 "Design Wind Loads on Other Structures".  Am I wrong? If so can anyone suggest what i should be doing?
Joseph R. Grill, PE