Tapped holes for structural member connection
Tapped holes for structural member connection
(OP)
Alright I got a project that the vendor is trying to use tapped holes and a thread bolt for all their structural load bearing member connections. Essentially, their members are connecting to HSS tube steel and therefor a nut cannot be attached. Is there a code in California that prohibits this type of connection. The engaged depth of the bolt would only roughly 1/2"-3/4" thick or so. All common sense is telling me the head of the bolt would need to be welded to the connector plate but they are saying no. The structural frame is enclosing a mechanical system and I'm sure there will be vibration let alone we have to conform to ASCE 7-10 codes as well. I attached a detail for reference. any suggestions?






RE: Tapped holes for structural member connection
We used to have connections similar to this in substations all the time. The easy option (if it meets your other project constraints) is to widen the connection in your section view to be wider than the top tube. We typically did it with a cap plate on the end of the vertical tube mating with a plate welded to the top tube, and 4 bolts between the two.
RE: Tapped holes for structural member connection
http://www.structuremag.org/?p=7611
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RE: Tapped holes for structural member connection
RE: Tapped holes for structural member connection
There are some papers that discuss methods for calculating stripping strength of threaded joints. I don't have them handy at the moment but Industrial fasteners institute has a nice 2 page tech bulletin that gives a straight forward procedure.
In general the thickness of the tapped element needs to be 1-2 times fastener diameter to develop the fastener but that is just based on my experience.
You want to make sure to get a decent number of threads engaged. UNC threads with thin material may mean you only get 1 or 2 threads engaged which I don't like.
RE: Tapped holes for structural member connection
RE: Tapped holes for structural member connection
EIT
RE: Tapped holes for structural member connection
RE: Tapped holes for structural member connection
Whether or not I'd use tapped holes would depend greatly on the loads and the size of hardware required. I believe you're outside of the RCSC recommendations and would be on your own for design. And if the loads allow, I'd be much more inclined to allow self drilling/tapping screws over some guy tapping into structural steel.
RE: Tapped holes for structural member connection
RE: Tapped holes for structural member connection
Dave
Thaidavid
RE: Tapped holes for structural member connection
As above, use the inserts if you absolutely have to use a tapped hole.