Strengthening of WF Beam

[Surya77]

I have a 30 ft long girder which is overstressed by 35% (Combined Bending IR of 1.35). I cannot add any supports in between. Only cover plates are the option. But adding one at the bottom is not providing the req capacity. Any ideas will help.

By the way the portion that is deficit in capacity is 14 ft (7 ft on each direction from center)

 

[JAE]

I would also chime in that the intersecting beams adequately brace the beam.

The key is to prevent overall section twist. The amount of force and stiffness is provided in AISC's specification - appendix 6 I believe.
You can simply calculate the required strength (twist moment at each brace end) and see very quickly that the shear bolts would usually more than adequately provide the strength.

Yes the bolts may be bearing only but a little slip won't change the fact that the beam is ultimately resisted from twisting.

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[racookpe1978]

Why not weld two 12x2x1/2 (or x 3/8) tubesteel members on both sides of the WF12?

Without increasing depth of the WF12, you'd add 4x 12-inch verticals to the outside of the WF, and - you'd add the anti-twist resistance several others have commented on.

The width of the original member is increased, but the connecting beams can be attached to the sides of the TS12x2.

 

[Surya77]

@raccokpe1978

Hey thanks for the reply

the issue we are facing is accessibility to do welds. It looks like they can access from top to weld plate to the bottom flange provided it is wider than the flange.

 

[racookpe1978]

A heavy tubesteel shape has substantial curves on every edge.

The ends of the two flanges on a WF shape are sharp, thus you have a "natural" V-shape "weld prep" for a full-penetration weld from the outside of the joint on the WF-TS connection that can be welded with no additional grinding other than clean up to remove mill scale, rust, and surface debris. A substantial stitch weld will be adequate, you will not need a full-length weld.

 

[jayrod12]

I think he's saying if you used tube steel he wouldn't be able to weld to the bottom flange as the only access if from the top.