Odd Beam to Column Connection (Steel)
Odd Beam to Column Connection (Steel)
(OP)
I have a 3 bolt connection of a beam to its supporting double angle connection. One of the angles is full length for 3 bolts, but the other angle is only long enough for 2 bolts. Therefore, 2 bolts will be in double shear while the third bolt will only be in single shear. This sounds an alarm in my head, but I cant reason why. Is there anything that allows 2 bolts in double and 1 in single shear connections? It seems like a combined welded/bolted connection, which should either be all bolts or all welds.
Any thoughts?
Any thoughts?






RE: Odd Beam to Column Connection (Steel)
With a double/shear single/shear bolt condition, I would think that the single and double shear conditions would have similar initial stiffnesses, either that or the bolt would deform slightly re-distributing the load to the others. Thus, each bolt would get exactly 1/3 of the load and the weak link would be the single shear taking 1/3 of the load.
Does this make sense?
RE: Odd Beam to Column Connection (Steel)
RE: Odd Beam to Column Connection (Steel)
I think looking at the failure of the single bolt might tell you a lot. If the single bolt fails in bearing on the plate, then the single bolt will deflect until the 5 double shear bolts can take up the load. If the bolt fails in shear thru the bolt cross seciton, then it may be a brittle failure, but that the bolt is likely to see some deformation prior to all-out failure. So it also likely to redistribute the load.
If you treated it like a 6 bolt, single shear connection - what is the demand/capacity ratio. This might tell us more.
-For what its worth
RE: Odd Beam to Column Connection (Steel)
RE: Odd Beam to Column Connection (Steel)
RE: Odd Beam to Column Connection (Steel)
If the beam works with only four double shear beams, I wouldn't worry about it. I don't know the loads, beam or the supporting member. If you must have 3 bolt rows in double shear, another way of making the connection safe to errect is to place a small beam seat made of a piece of angle to temporarily support the beam that is placed first on the column. Then once the other beam is in place, all bolts can be put in the common holes.
RE: Odd Beam to Column Connection (Steel)
RE: Odd Beam to Column Connection (Steel)
KHS - Any AISC steel manual will have those.
RE: Odd Beam to Column Connection (Steel)
If the answer is yes, I wouldn't have any more worries.
I usually repeat to myself that wherever steel is added to a structure, this cannot harm the structure (except under very special conditions: high fatigue loads): so if you can take the loads and fulfil code rules after the third bolt is withdrawn, then you are done.
If you need the third single shear bolt, then I would evenly divide the load by 5, but conformance to code is a more delicate question here: I can't comment on this as I don't know your standard.
prex
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RE: Odd Beam to Column Connection (Steel)
In its most simplistic state, if all the load were initially taken by the single bolt, it would deflect or fail then transfer load to the two bolt system, which would either resist the load or fail depending on magnitude. Conversely if all the load were initially taken by the two bolt system, then failed, the third bolt is irrelevant.
RE: Odd Beam to Column Connection (Steel)
I agree with Ron; our practice is to treat the single shear bolts as erection bolts only, and do not figure them in the equation when evaluating offset connection capacity. Evaluating the connection as has been suggested seems only necessary in the (uncommon) event that there is not enough room in the connection angles for the extra (unaccounted) bolts.
David
RE: Odd Beam to Column Connection (Steel)
Otherwise, I don't see why 2 bolts in double shear and 1 bolt in single shear would be different than a single bolt sheared 5 times, thus each shear plane (if all things are equal) would take an equal load amount.