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## Re: [TowerTalk] PIPE ANCHORS

 To: K8RI on TT , towertalk@contesting.com Re: [TowerTalk] PIPE ANCHORS Grant Saviers Sun, 30 Oct 2011 19:59:04 -0700 mailto:towertalk@contesting.com>
 ```Like your logic, but squares have more steel "further out" from the neutral axis so they win (or at least moment calculators say so) see http://www.engineersedge.com/section_properties_menu.shtml Compare a 4" od x 3" id pipe with a 4" sq od x 3.5" id sq tube. Many shapes are there to play with. About the same moments and the pipe is much heavier. 5.5 sq in cross section of steel for the pipe and 3.75 sq in for sq tube, a 50% increase in weight per foot for tube. And there is a diagonal moment calculator for squares (squares win in all cases). What am I missing? (of course there is a lot more to structures than this one number) Grant On 10/30/2011 4:48 PM, K8RI on TT wrote: > On 10/30/2011 2:51 PM, Jim Lux wrote: >> On 10/30/11 10:39 AM, Grant Saviers wrote: >>> A couple more comments, some not covered before: (all comments w/o >>> engineering calcs - YMMV) >>> >>> 1. Square tube is stiffer/stronger than round pipe or wide flange beams >>> (I-beams) of same #/ft.. >> Hmm. I'm not sure this is true. Bending strength goes as the radius to >> the 4th power, and for a given perimeter, a circle has the section >> moment. (sort of like a circle has the most included area for a given >> perimeter). >> >> Cross sections with right angles are easier to use in construction, >> especially for bolted connections, and a I beam typically has more metal >> farther from the center than a square tube (which is why they use that >> shape). >> >> However, in "practical sizes commonly sold" it might be true that >> squares are stronger than circles. > I think you will find that per unit of weight the pipe is stronger than > other shapes which have their maximum strength along one or more axises. > > Structural steel tube like pipe has a welded seam, BUT pipe is much > softer and bends far easier than structural steel. DOM (which is also > seamless) of a given wall thickness is even stronger and more rigid. > IIRC DOM is also available in multiple alloys. > > Most towers like 25G and 45G depend on shape for most of their strength. > > 73 > > Roger (K8RI) > > _______________________________________________ > > > > _______________________________________________ > TowerTalk mailing list > TowerTalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk > _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread Re: [TowerTalk] pipe anchors, (continued) Re: [TowerTalk] pipe anchors, Cqtestk4xs Re: [TowerTalk] pipe anchors, Chuck Sudds Re: [TowerTalk] pipe anchors, Jim Lux [TowerTalk] PIPE ANCHORS, sgtokie Re: [TowerTalk] PIPE ANCHORS, Grant Saviers Re: [TowerTalk] PIPE ANCHORS, R. Morris Re: [TowerTalk] PIPE ANCHORS, Jon Pearl - W4ABC Re: [TowerTalk] PIPE ANCHORS, Jim Lux Re: [TowerTalk] PIPE ANCHORS, Jim Lux Re: [TowerTalk] PIPE ANCHORS, K8RI on TT Re: [TowerTalk] PIPE ANCHORS, Grant Saviers <= Re: [TowerTalk] PIPE ANCHORS, Jim Lux Re: [TowerTalk] PIPE ANCHORS, Grant Saviers Re: [TowerTalk] PIPE ANCHORS, Dorn Hetzel Re: [TowerTalk] PIPE ANCHORS, Dorn Hetzel Re: [TowerTalk] PIPE ANCHORS, Jim Lux Re: [TowerTalk] PIPE ANCHORS, Kipton Moravec [TowerTalk] (Concrete filled anchors) was Re: PIPE ANCHORS, K8RI on TT Re: [TowerTalk] PIPE ANCHORS, Bill Gillenwater Re: [TowerTalk] PIPE ANCHORS, Jim Lux Re: [TowerTalk] PIPE ANCHORS, Dorn Hetzel