×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Cutting Bottom Flange of Steel Beam (In Place)

Cutting Bottom Flange of Steel Beam (In Place)

Cutting Bottom Flange of Steel Beam (In Place)

(OP)
I have a project under construction and have a beam that was specified as a W12x50, but they installed a W21x50. The other way around would have been a lot worse, but there are two ducts that need to pass under this beam and a certain ceiling height is required. This is an interior beam that supports a floor and is not part of the lateral system. The concrete deck has already been poured. The architect has asked if the bottom flange could be cut in the area the ducts need to go, so I'm looking into the possibility.

They want to cut out 5 1/2" from the bottom of the W21x50. That would leave enough depth to place horizontal stiffener plates at 14" below the top of beam. My quick preliminary check shows it wold work with that depth and appropriate stiffener design, but I realize there are a lot of things to consider: cutting heat, temporary shoring, preheating, welding inspection, stiffener design, etc.

I would make them shore the floor to take load off the beam and shore the beam on each side of the cut prior to work. I have enough depth to work with that I could add stiffener plates away from the cut edge about 1.5 inches. That will move the stiffener plates away from the heat-affected zone of the cut edge. All welds would be inspected.

I would appreciate any additional thoughts on this situation.

RE: Cutting Bottom Flange of Steel Beam (In Place)

You're saying all the right stuff regarding shoring, preheating, etc. I think that you've got this down cold. KootK approved.

If you're going with only horizontal stiffeners, I actually think that you could get away with no shoring / load removal here. You could install the stiffeners and then make the cut. I guess it depends how agressive and contractor friendly you want to be.

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.

RE: Cutting Bottom Flange of Steel Beam (In Place)

Definitely, the beam should be supported each side of the cut before commencing the work. You could weld an angle each side of the web just above the duct and extend them well past each edge of cut. The angles would replace the cut flange and stiffener plates may not be required.

BA

RE: Cutting Bottom Flange of Steel Beam (In Place)

Questions:

1) simple span beam?

2) where in the span(%) will the reduced section occur?

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.

RE: Cutting Bottom Flange of Steel Beam (In Place)

I don't see shoring by itself necessarily removing existing stresses from beam, just preventing additional stresses.

I like BA's concept of welding the new bottom flange, ie angles each side, prior to cutting off the existing bottom flange, as the reverse order would allow further accumulation of compressive stress in the top flange should there be any movements in the shores.

RE: Cutting Bottom Flange of Steel Beam (In Place)

This might be a dumb idea but I'll mention it anyway. That is, if you do shore it, at that point might it be easier/cheaper to just replace the beam with the W12 originally specified? Just something to consider.

RE: Cutting Bottom Flange of Steel Beam (In Place)

@ Archie, It might have form deck welded or composite floor, making it hard to remove. Also, might be hard to get out of the room/building

RE: Cutting Bottom Flange of Steel Beam (In Place)

Ah yes, good point. Also, getting the new beam in there. Getting the old one out could be helped with a cutting torch, though.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources