Quote:
Originally Posted by DarkArts
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I assume the section size given is for "plain" CHS welded to a base plate. How would this change for a pier that includes full-height, fully-welded fins?
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So I just did a quick exercise to see what benefit there would be to add stiffeners. Assumption was a circular tube with 4 equally sized stiffeners (at 12, 3, 6, and 9 o'clock) full height. Stiffener plate thickness was set to 10mm.
With no stiffeners, you'd need a 219X6.4CHS.
With the same design parameters, and assuming the reason you want the stiffeners to reduce the CHS size, I dropped the CHS size to the lightest (thinnest wall) of the next diameter down - 168x4.8CHS. To get the same stiffness as teh 219x6.4, the stiffener plates need to be 57mm long (in reality you'd use the next off-the-shelf flat available, which is 65x10).
Thing is, 168x4.8CHS with 4 stiffeners 57mmx10mm weighs 37kg per metre. A 219x6.4CHS with no stiffeners weighs 33.6kg/m. So for the same stiffness, no plate stiffeners is lighter (ie more efficient). Usually cost is measured in kg/m too - so it's cheaper. And that's ignoring the fact that plate stiffeners require more welding too.