sorry for another post, but here's a real interesting doc focusing
on fatigue (in traffic sign anchor supports), from the National
Cooperative Highway Research Program...univ. research report.
They have big problems with wind induced oscillation with traffic signs
(they call it galloping)
last updated 10/19/2004
http://gulliver.trb.org/publications/nchrp/nchrp_rpt_469-a.pdf
page 62 is interesting. They talk about the importance of correct tensioning
and the difficulty of it (torque being an unreliable indicator).
Interestingly, they say proper alignment of the anchor bolts can be more
critical
than tensioning.
appendix A, starting on page 86, summarizes their recommendations.
They're very clear on specifying ASTM F1554.
page 133 is interesting also. they mention another aspect for resistance
to fatigue cracking, what they call "notch toughness"
interesting reading about the "galloping" and other oscillations. Makes
it seem like there are a lot more issues in antenna/tower modelling than
our simple wind load models. I.e. they do a lot more analysis/engineering
in cantilever traffic sign design.
-kevin
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|