Monday, November 1, 2010

bolted steel connection modification

-Standard AISC steel shear connection, single shear plate bolted to the web of a beam and welded to an embed plate in a concrete tilt-panel.

-Existing building, finishes up and this will have to be a weekend job probably.

-Third floor beam, temp shoring and jacking pretty much out of the question.

-Dead loads in place, building occupied.

-It was determined the existing shear connection was about one bolt short or about 6 kip.

 

1.       Does AISC allow you to add the strength of an additional weld from the shear plate to the web of the now-bolted beam?

2.       To maintain a connection that allows some rotation to maintain a pin-pin assumption, the weld could be placed only near the bottom. I’m winging this email so pardon my mechanics of materials memory….

3.       The bolts should be in full bearing condition and local deformations for the most part should have taken place inside the connection, correct? I know it depends on % of dead and live load, size of the holes (13/16” diam with ¾” dia bolts I think), etc…

4.       Alternatively, what about adding a shear plate to the opposite side of the web and turn this into a double shear connection? They could take the nuts of the existing connection, slide another shear plate on, weld it to the embed plate, then tighten up the bolts… The problem I see with that is making sure the bolts are bearing on the new plate once it is welded up there and it is not just there for peace of mind. I am worried the connection would have to yield slightly to begin bearing on the new plate, but maybe that is acceptable? Would I have to use a slip critical connection to ensure load transfer?

5.       Third option is it may be possible to add a stiffened angle seat below the beam. But again, how do get it to share the load and not be just eye candy… I think in terms of sharing the load this is worse than adding weld.

 

Any references to AISC or other advice would be greatly appreciated.

 

Thanks in advance,

Andrew Kester, PE

Florida

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