Uplift on continous steel beam 1

[DoubleStud]

I have a ridge than spans about 27.5 ft and 12.5 ft. I specified W14x48 and then (2)-LVL on the small span. The contractor wants to put steel beam the whole way (40 ft). He does not mind long heavy steel beam (unlike most residential contractor). When I analyze it as a continuous beam, I will have about -632 lb uplift with balanced load or -4262 lb uplift with unbalanced load. This is in the snow country. I am not sure I like this. My question is this. Is it possible to install the whole beam 40 ft long. Then next at the mid support you cut the top flange and bottom flange? That way the beam will still have continuous web but not flanges? Will that create a hinge to relieve the uplift? Or maybe just cut the top flange?

 

[driftLimiter]

40ft is readily available if they say that they can install it then I see no issue with that part of it. I dislike the idea of making a pseudo hinge by cutting the flanges.

Other options would be do a propped cantilever on the long span and drop in simple span on the other, frame the column high and shear connection on each side, or make a load path for the uplift.

I think using two span probably isn't that much more work than one cont span if you had a dropin with a bolted shear splice.

 

[dik]

If it's a problem, can you sawcut the top flange and the web?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[DoubleStud]

The mid support is (7)-2x6. So you are saying to cut it right in the middle of support and cut to top flange and the web? Just cutting the top flange is not enough in your opinion?

 

[dik]

Cutting the web reduces the moment capacity significantly... it depends on how much you need to reduce the moment. You can do a quick moment check on the resulting inverted 'T'shape to determine the moment capacity/stiffness.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[BridgeSmith]

I agree with dik; I also recommend cutting the top flange and web. You'll still have significant moment capacity if you keep the web intact, and if you exceed the remaining moment capacity, you'll yield the web and create a potential for fracture. Leaving just the bottom flange allows significantly more rotation without significant strain of the steel, and reduces the moment capacity to a very small value. The web is also less steel to cut than a flange.

 

[dik]

I did that on a project about 50 years back to make some headroom... not to reduce stiffness...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik