Framed Beam Connections

[mjohan]

What is the most common type of bolt connection for a steel beam to angle, knife plate, etc..., slip or bearing type connection?

If you analyze the connection as a bearing type connection, how, when built, can the designer be assured that the connection is indeed a bearing type connection? It seems that by tightening the nut would most likely create a slip/friction type connection.

Mark

 

[JAE]

If you design a connection as a bearing connection, and for whatever reason the bolts are tightened it really doesn't matter as you, the designer, have based your design on a connection where slight slip is acceptable and the ultimate strength of the connection is based on the bearing strength which is higher than the slip critical capacity.

 

[mjohan]

Thanks JAE,

I suppose my confusion arises from the statement in the AISC manual regarding framed beam connections. I don't have the book right now but their is a statement that says "in the unlikely event the connection slips into bearing... the steel must be checked for bearing stresses" (that statement is not verbatim). The design examples all seem to reference slip critical connections with a bearing connection as a check for the beam bearing stress "if" the connection slips. All steel connections will be torqued to some degree, whether specified on plan or not, and would that create a slip critical connection? I guess my point in all of this, is should we use the lesser values assigned to slip critical bolts, in lieu of the bearing type bolt values.

Your point regarding the acceptable slip in this type of connection makes sense to me. I am curious if this has ever been a documented concern, though, in residential buildings. If the connections did slip, would that introduce an impact load on the bolts and also create some bangs in the building?

Maybe I am making a mountain out of a mole hill, but your thoughts are very much appreciated.

Thanks
Mark