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Re: ASCE 7 Wind Loads on Bare Steel Framing - Opinions Wanted

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A lot of wind load studies came out of the University of Western Ontario doing wind tunnel tests on models of structures, under Dr Davenport in the 60's thru 70's. Others also were doing similar tests elsewhere, but I think Davenport was one of the first. All of these tests have been reflected in the codes along with results from testing in actual structures. This does not help but gives a little perspective.
Gary

bill(--nospam--at)polhemus.cc wrote:

Lots of pipe racks to look at. Very fascinating.

(P.S. Not really).

Years ago when the ASCE 7 standard was focused almost exclusively on building structures, we used to have rules of thumb for applying wind loads to these kinds of "lattice" structures like pipe racks and large structural steel bare frames. There were all sorts of arguments about "shielding" of one member from another, for example.

ASCE published a guideline back in the 90s ("Wind Loads and Anchor Bolt Design for Petrochemical Facilities") to help establish some consensus regarding how to apply loads to these structures. It was based on the state of the art at that time - ASCE 7-93 or -95 IIRC - which of course has changed quite a bit since then.

ASCE 7-05 was significant in that it added quite a few commonly-seen but previously unaddressed systems, like canopy roofs and braced steel towers, to the provisions for calculating wind loads. But there are still some questions in my mind at least.

It seems easy enough to apply provisions for "Open Signs and Lattice Frameworks" (ASCE 7-05 Fig. 6-22) and "Trussed Towers" (Fig. 6-23), for example, but it is NOT obvious that these are correct.

It seems to me that a colleague and I did a comparison with the ASCE "Petrochemical Facilities" publication procedure, and ASCE 7-05 using Fig. 6-22, and it came pretty darn close. I have been a proponent of going with ASCE 7-05 but I have "older" colleagues who don't much like change, and insist that since the older ASCE "Petrochemical Facilities" publication was good enough "then," it should be good enough now.

Opinions?


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