Burned Holes in Bearing Type Connections. 1

[lokk]

What Problems arise when you have uneven bolt holes in a bearing type connection? I have a situation where I am relying on bearing, but unfortunately the contractor burned the holes versus punched holes. Does this cause the connection to become slip-critical?

 

[dik]

The holes may have to be reamed and larger bolts installed. As slip critical, if bearing loads work, then the slip critical conn will be quite a bit shy of capacity. You will have nearly twice the number of fasteners.

Dik

 

[dbuzz]

As far as I understand it, we aren't allowed to accept 'burned holes' for connections here in Australia.

 

[SlideRuleEra]

Agree with dik and dbuzz about burned holes being unacceptable. Concerning acceptable oversized holes (drilled, punched, reamed), see Chapter 9 in the free .pdf download "Guide to Design Criteria for Bolted and Riveted Joints" from the Research Council on Structural Connections, at this link

http://www.boltcouncil.org/guide1.htm

http://www.SlideRuleEra.net

 

[Qshake]

The problem that arises is simple, all bolts don't bear an equal amount of the load acting on the connection. Thus it's possible to compromise the design intent of the connection.

Does this cause the connection to become slip-critical - no, the action of burning oversized holes doesn't itself cause the connection to be slip critical. In fact most bearing connection bolts are not even tensioned to the required level to achieve a slip critical connection. Typically they are simply snug tighten with a spud wrench and ironworker effort which may be different in the morning than the afternoon.

Even slip critical connections are designed using only minimal increase in bolt holes, the reason is that in the ultimate condition of slip, the connection is expected to resist load in bearing. This adds some redundancy.

Ream the burnt holes and use oversize bolts.




Regards,
Qshake

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[Tmoose]

If the assembly is done is there room to allow you to add a few bored/drilled holes to provide the right number of "fitted" Bolts?