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[SEAOC] Re: [SEAOC] Wind Pressure Coefficients (Cq)

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I would suggest that you get a copy of the wind commentary to the UBC, call
209 682-6026. (I have the 1991 edition, Is the 1994 version available?) I
have found it to be a good reference. It also references ASCE 7-88. The
commentary mentions that Cq for open frame towers is conservative, but for
tall flexible towers Ce is not. The UBC does not provide guidance for
dynamic effects, icing and increase wind speeds at hills and escarpments. I
realize I did not answer your question, but these references should help.

Jeff Smith

>Can someone explain why the wind pressure coefficient (Cq) for Open-Frame
>towers (UBC 94) is so much higher than other structures?  According to UBC 94
>Sec. 1621, Open-Frame Towers are "Radio towers and other towers of trussed
>construction ..."  I suspect shape factor of assembled trusses has something
>to do with it. 
>Secondly, I am designing 60' tall x 15' sqaure open tower, assembled with
>four steel tube columns at the corners and connected at the top with steel
>tube beams.  No diagonal members in between the columns; just tall free
>standing columns.  What Cq factor should be used?