huangyhg

beam erection seat
i have a wide flange beam that attaches to a column with a single shear plate bolted connection designed for bearing (not slip critical). the contractor wants to use an erection seat angle welded to the column and left in place after construction. it seems to me that the erection seat will prevent the bolts from engaging the load from the beam. i couldn't find anything in the aisc code or eng-tips forums about this situation.

i have projects where beam erection seats were provided. i left them in place. the bolt diameter is only 1/16 larger than the bolt. this means the beam can slip 1/32!!! not much movement for simply supported beam.
i think you are worrying too much. see it as positive thin and some sort or redundancy. i would not rely on the seat angle to support the beam end unless proper engineering is done on the seal angle and its connection to the column.
you can ask the contractor to remove the seat especially if it is exposed.
at the the strength limit state the angle seat may fail but your web side plate should be satisfactory. i wouldn't be too worried about it.
on the one hand, if the erection seat prevents the bolts from engaging the load on the beam, that means the load's being supported. on the other hand, if the seat isn't really designed to take service loads, it could fail and that could mean trouble. depending on where the structure will be, you might want to check against seismic design recommendations. fema 350 - recommended seismic design criteria for new steel moment-frame buildings can be downloaded at
if you feel the need, have the seat angle bolted rather than welded. 'failure' would then transfer the load to your designed bolts.
your design was for a shear tab that has the ablilty to bend. your problem simple. you have a contractor that wants to erect on a seat angle to make erection faster. that appears to be fine. but if you take into consideration that there will also be a possible problem with a number of other factor then you will also have to agree that is not your design.
the fact that shear tabs are designed to bend in two directions and to twist. that is right shear tabs twist,
so if you lock in the beam at the base of the beam below the shear tab the tab itself can not work as a shear tab always.
if the erector wants to use a erection seat tell him to provide a 1/4 gap between the top of the seat angle and the bottom of the beam and bolt the beam to the seat angle for erection, but remove the bolts and the shim plate after final bolting of the flange.
to cover your self you should notify him also that his engineer will be responsible for the design and safty of the seat angle.
if you approach it this way you do not have to check the project for there extra connections, and you will not be have to wonder any more.

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