Modifying a Cambered Beam

[MiscMetals1259]

I am a PM with a Structural Steel contractor. Another PM in the office has a Cambered Beam that will
not fit into the building (renovation)due to size. The solution is to cut the beam in halve, and re-weld in
the field. Will this compromise the purpose of the cambered beam after installation?

 

[phamENG]

Probably not, but there are a lot of things that could influence it. Best bet is to contact the EOR and discuss the site constraints and alternatives to come up with a solution. He/she will be much more familiar with the project and the conditions than we are and is likely the only one qualified to make that decision.

 

[kipfoot]

I think you'll still have the camber after the new splice is made. The engineer of record will have a recommendation about where on the span to make the splice. Probably cut into 2/3 and 1/3 pieces rather than half and half, if that still allows you to get the beam in place.

 

[dhengr]

MiscMetals1259:
Cutting 2 or 3” of depth out of the middle of a web of a cambered beam isn’t something you are likely to do successfully, in the field or otherwise, if you have to ask this question this way. We would need much more loading, geometry, original methods and rationale, and engineering info. to even start to approach this problem. The field labor isn’t free or often top quality or overly experienced, you won’t have the right equipment in the field either. You will undoubtedly change the final, new, camber in any case. You would probably be better off selecting and properly sizing a new beam and cambering it for a normal replacement. But, if they had to camber it in the first place, and you pick a shallower new beam, you might not be solving a lot of the problems.

And, after all that, a new question…, what does “The solution is to cut the beam in halve, and re-weld in the field” really mean? If you are trying to cut out a couple feet in length, I’d cut a foot off each end and save the rewelding, and rework the bm. bearing pls. Study the cambered shape and reasons for it and you might do all you cut-off at one end, without changing much. There is just too much that we don’t know.

 

[BAretired]

There is not a huge advantage in offsetting the splice to the 1/3 point.
For a uniform load W, M = WL/9 instead of WL/8.



BA

 

[phamENG]

My answer was assuming that the beam is correct, but you can't fit it through the front door.

If dhengr's take is correct and the beam itself was fabricated wrong or there is some permanent obstruction that will make installing the beam impossible, then my stance is changed and it's probably best to start over as he suggests.

In either case, the EOR is the best - and most appropriate - person to ask.

 

[r13]

Yes, pass the ball to the EOR to get a feasible design, without the need of un-authorized modifications in the field.