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Re: Bolted steel connections -- flame-cut holesl

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     Nels Roselund wrote:

<<I'm working on strengthening of a 1898 steel frame building.  "Carnegie" 
is rolled into the structural steel members.  The testing lab has advised 
that the chemistry of the steel is not compatible with the modern welding 
process; I've designed all connections to existing steel to be bolted.  The 
steel is HARD; some cannot be drilled with hand-held equipment.  The 
Contractor is using mag-drills and that is working O.K.  However, some holes 

are not accessible to the mag-drill equipment.  The contractor is proposing 
to flame cut the holes 1/8" undersize and to ream to the specified size; no 
flame-cut edges are to remain in the hole.  Is there any problem with this 
procedure?
     
What about using slip critical high strength bolting?  Is there any 
advantage or
disadvantage considering that the connection is secured by clamping remote 
from 
the hole rather than by bearing on the hole?>>


Your solution seems reasonable.  I offer the following comments:

1)  Consult with a metallurgist for his opinion on whether this "hard" steel 

will become unacceptably brittle as a result of the flame cutting operation.

2) Make sure that all of the burrs are removed in the reaming operation to 
allow
proper "clamping" of the connected parts.  

3) Make sure that your connected parts match the requirements as specified 
in 
the AISC Spec for high strength bolts.  Especially note the requirements for 

"Joint Assembly and Tightening of Connections Requiring Full Pretensioning".

4) Make sure that you design for the "slip critical" values as specified by 
AISC.  Note that the AISC "High Strength Bolting" specification gives 
different 
values based on the coatings classification.  The manual design aids are 
calculated for Class A coatings.  You might have Class C coatings with 
higher 
allowables.

Good luck,

Rick Drake, SE
Fluor Daniel, Inc.