Washer Requirement for Bolted Bearing Connection?

[dodson]

I have a project with wide flange girders, wide flange joists at ~8' oc supporting a 5" deck with slab. For the joist to girder connections I have a standard double angle bolted connection. The fabricator used short slotted holes in all of the angles. He used washers on the nut side of the bolts but not the head side. He is using a traditional bolt with a smaller head instead of the twist off bolts with larger heads causing part of the short slotted hole to be exposed. The inspector is telling him that per Section 6.1.12 in 16.2 of AISC, that the entire hole must be covered up, which would required him to remove and re-install every bolt on the job. My question is, since this connection is strictly in bearing, is dishing really a concern?

 

[gtaw]

It depends on whether the connections are required to be pretensioned, slip critical, or "simply" categorized as bearing connections.

 

[kingnero]

It's good practice, even if not required by standard or code, to use washers over slotted holes! Contact pressure goes up to approx. the double, as the contact area halves.
Especially so, if the slotted holes are ment to allow for thermal expansion. Which is another jar of pickles alltogether.

 

[dodson]

In this condition, the slot direction are perpendicular to the load and thermal expansion is not a concern as it is in a heated garage. So the bolts are purely in a bearing condition.

 

[kingnero]

If you want to know if dishing is a concern, check bolt tension (can be estimated from the mounting torque) and contact surface (by undoing the bolts and checking the imprints, or by CAD using the true dimensions), divide one by the other to get the contact pressure an evaluate against the yield of the base material.