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RE: Slotted HSS/ Gusset Plate Connection (Help!)

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Title: RE: Slotted HSS/ Gusset Plate Connection (Help!)

>....slotted HSS/gusset plate connection...AISC recommends...that the
>length of the weld shall be equal to or greater than the O.D. of the pipe...
>My interpretation is that this is a recommendation and not a
>definite requirement and that a shorter length may be used provided the
>numbers add up.

There is a requirement in AISC Specification Section J2.2b that longitudinal fillet welds for flat-bar tension members must be at least as long as the distance between them. This is a time-honored requirement that originated back in the 1930s when there were just hard-and-fast geometric requirements that addressed shear lag effects on rupture strength. It remains there today even though more general and explicit shear lag provisions exist today.

If you think of HSS and steel pipe as curved plates, you'll see the basis of our recommendation in the HSS Connections Manual. However, by the letter of the law, if you address shear lag effects in the tension rupture calculation, and all the other applicable limit states, you could get by with less weld.

Note that the other general provisions for minimum and maximum weld lengths apply too.

>Cheng and Kulak (AISC Engineering Journal, 4th Qtr, 2000)
>suggest that ... the stiffening effect caused by the gusset plate
>precludes shear lag fracture as long as the weld length is
>1.3 times the pipe diameter .... Any chance that AISC will
>reexamine this?

We're looking at that right now for the 2005 AISC Specification (the Unified Specification). Personally, I think the Kulak paper presents great work and a very positive and practical modification that can be made to our provisions for shear lag.