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Fw: [wind_haz_mit] Fw: Wind loading[Subject Prev][Subject Next][Thread Prev][Thread Next]
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- Subject: Fw: [wind_haz_mit] Fw: Wind loading
- From: "JCohen" <jccpc(--nospam--at)email.msn.com>
- Date: Sun, 17 Oct 1999 22:19:56 -0400
Another response on wind loading from the wind_haz_mit egroup. James Cohen Website: http://u2.expertpages.com/jccpc -----Original Message----- From: Ernie Jones <ernie(--nospam--at)eriinc.com> To: JCohen <jccpc(--nospam--at)email.msn.com> Date: Sunday, October 17, 1999 15:27 Subject: RE: [wind_haz_mit] Fw: Wind loading To whom it may concern; I am unaware of any testing on combined wind effects for such a situation. Actually, outside of the three and four sided trussed tower force coefficients, based of wind tunnel testing, and latice framework coefficients, I'm unaware of any other published references. We have a similar problem in the EIA/TIA TR 14.7 committee I work on. This committee writes the ANSI/TIA/EIA-222 Broadcast Tower Standard. We only give wind sheilding if the feedlines, climbing ladders, or other members are fastened directly, and not beyond a face of the tower. The idea is that these members play the same role as structural members in the faces, and the face with the highest "e" (Af + Ar / Ag) governs. The Ae and Cf are taken from the "e" of this face. However, if the feed lines, ladder, etc. are inside the triangular or square tower, then they have to be taken as seperate members in free space, with the highest applicable shape factor used. We certainly know that some wind sheilding exists, however, without a proven method to calculate this we cannot put a realistic number to it, so we take the conservative route. There is some limted information on interference effects in a reference titled "Wind Forces in Engineering" by Peter Sachs (Pergamom Press). They summed up their limited work by saying a body which is windward of another will affect the wind forces on the second one, if they are within 6 diameters (widths) of each other. If greater, then consider them to have no wind sheilding effect. They give a shape factor for both bodies together based on their separation. Hope this can be of some help, although I know it does not provide specific data to keep from using somewhat of a conservative combined calculation method. Regard, Ernie Jones, P.E. ERI at (812) 925-6000 Phone
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