reinforce existing i-beam

[CPBe]

Hello all,

I have a somewhat unique issue that I've been tasked with and would appreciate feedback from an experienced group.
There is an existing roof structure (which all preliminary calc's indicate was designed to hold roof construction, live load, & some snow) which is getting a new 2,600 lbs fan.
Hoping to reinforce the existing W8's to keep deflection down (and also help w/lateral-torsional buckling).
Welding to the existing members is not an option.
My current thought is to bolt (2) C6's to either side of the W8 web along its full length, and frame the opening with some C6 as well - see preliminary sketch below:

Does this seem feasible? Is there maybe a more efficient way to achieve the desired effect?
Any feedback/thoughts/concerns would be greatly appreciated.
Thank you!

 

[lexpatrie]

A W8 wouldn't typically be all that sensitive to LTB, these are slash were column sections, after all.

If you attach the image (jpeg) using the "image" link (the camera icon) you'll probably get more engagement.

 

[BridgeSmith]

What you've shown looks like a reasonable solution.

Depending on the flange width of the W8, and subject to other constraints, the option of a bolted cover plate on the bottom flange may also be effective, but would require less steel.

If the long bolt shown goes through the flange of the channel, you'll likely need a tapered plate washer to correct for the taper of the flange.

 

[cliff234]

Is there enough headroom below the existing beam to weld a new HSS? (It would probably need to be no deeper than 2" or 3".)

If so, use an HSS that’s at least 2” wider than the W8 flange width and weld the HSS to the tips of the W8 flange easy-to-install downhand fillet welds. This is easier and less expensive than field drilling holes and installing the new C6’s.

A secondary benefit is that adding an HSS below the W8 is more structurally efficient than bolting C6’s to the W8 web because it increases the total depth of the member.

(Also, your sketch shows 3/8” bolts. I’ve never seen 3/8” diameter structural bolts. ½” diameter is the smallest structural I’ve ever seen.)

 

[human909]

If possible I would prop the existing beam during installation. Otherwise your new members won't share any of the existing load. Likewise keep your bolting tolerances low as the new beams may not participate bearing new load until hole clearance has been taken up.