huangyhg

canopy tie rods
i have an aluminum substructure canopy that has tension tie rods that attach the outer most part of the canopy back to the structure. my problem is that under wind load these rods will go into compression. the rods are 3/4" in diameter and about 13 feet long. is it correct to add an additional rod that will go down and attach to the building for the uplift case. i understand that the rods are non-linear and i have always been under the impression that they cannot take compression. could someone please help me. thank you for your time and attention.
val courtney, pe
optimal engineering, inc.
you are correct...thin rods like that would be highly incapable of resisting compression.
i have seen some canopy manufacturer's use small pipe (to give the slender look of rods, but can take some compression for uplift).
courtnvm....i have analyzed hundreds of canopies, many of which have the same conditions you posed. we generally use a 2" or 3" diameter aluminum pipe for such conditions. a 3/4" dia. rod of that length will not take the compression resulting from a wind load. euler's buckling procedure can be used to check the critical load.
i want to thank all of you for replying to my post and giving some reassurance and greater insight. i was able to get a fixed connection back to the structure therefore eliminating the tension tie rod under the wind uplift. if i would use an aluminum pipe, what is the typical connection detail.
val courtney, pe
optimal engineering, inc.

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