Existing steel tubing purlins need to be extended 2

[delagina]

I have existing purlins made of steel tubing. It needs to be extended 3' overhang. What is the best BOLTED moment connection detail for this? Since it's a purlin it has existing roof. They want roof extended 3' overhang.

This cannot be field welded for a couple of reasons.
I work inside a plant. Welding requires hot work permit which they (boss) prefer not to do. Electrical guys don't want any field welding done because it may cause issues with the existing electrical equipment that the roof/shed is covering.

The detail I have come up is shop weld a plate inside a new tubing purlin, with about 1' of plate protuding out. Then shove in the protruding plate inaide the existing purlin and bolt it.

 

[delagina]

Got a suggestion from roofing contractor to bolt it from the side. I will add new purlin to the side of existing purlin. The bolts will be on shear but it does not have a huge load. Any comment about that detail?

 

[CANPRO]

delagina, I suggested something similar about a half dozen posts ago. I think installing a new purlin next to the existing is your best chance at making this work.

 

[KootK]

The bolts will be on shear but it does not have a huge load. Any comment about that detail?

Depends. Does the new member go into the building and attach to the back-span support as CANPRO suggested? If so, I like it. Or does the new member stop at the exterior face of the building? How long is the existing cantilever?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KootK]

Add this to the heap-o'-suggestions. Maybe throw some neoprene washers in there to deal with the "rattle" that dik mentioned.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.