Precast planks @ New WF BMs

[kaisersoze]

I am reviewing shops for a project designed by another engineer. The floor framing is precast planks sitting on support inside the web of the W30 bms (I hate always hated this detail). The precaster is asking if he can cut off about 4'-6" portion of half the top flange to slip in his planks and then he would weld flange back on. I can't see any other way for him to be able to install the planks but I am very nervous about how to approach this. If I give him the go ahead, I am going to ask: 1) The bm be shored until the work is done, 2) Cut the flange starting about a 1' from the end of the bm.

But how on earth is he going to restore a full pen weld when there is plank on one side of the flange? Has anyone run into this issue before.

Thanks,

Kaiser

 

[msquared48]

Pre-weld a back-up bar to the underside of the flange.

I do not like the idea of messing with the flange though...

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Lion06]

It's not an ideal detail, but it's better that it's the compression flange than the tension flange.

Did this concern get raised before this system was chosen?

 

[msquared48]

I think that if the steel beam was, say 30 feet long, and the panels were, say 4 feet wide, you could cut a 5 foot long section of the flange off toward one end of the steel beam, lift the panel in place and slide it along the remainder of the flange into the location desired, then reweld the removed section of the flange back. This would minimize damage to the steel beam.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[UcfSE]

Can you weld a ledger plate to the bottom of the bottom flange and fabricate the planks short enough to fit?

 

[csd72]

A classic example of what happens when the constructability is not adequately considered in the initial design.

I take it that you have already considered sliding them in from the ends.

 

[kieran1]

Agree with UcfSE, personally I wouldn't even consider cutting the beam flange.

The method of installation also needs consideration. I seen alot of beams twist dangerously when only loaded on one side.

Kieran

 

[csd72]

What about twisting them horizontally into place? You could get most of them in that way.

Hard to tell as you have not given any info on spans

 

[Brad805]

In the future you should look at something like the Piekko system.

http://www.peikkousa.com/Default.aspx?id=536463

We welded a ledger plate to the bottom flange of the beams on one project, and I worried about that detail for a long time. It worked out fine, but I really hated the detail.

Brad

 

[Lion06]

I do see one problem with providing a bottom plate and cutting the plank short. Depending how the system is topped and tied together, I could see problems if the plank spans on opposite sides of the WF aren't equal or even with unequal loading.

 

[slickdeals]

I am wondering what the reason for such a detail might be? Sounds like a pain in the butt.

What fills the gap between the top of plank and top of beam? The W30 is fairly deep.....Is the top flange of the beam unbraced the entire length?

 

[kaisersoze]

Thanks for all the replies fellas. Here is the situation in a bit more detail. Three bays of planks, with foundation walls @ each end and (2) W33x140ish in the middle. Span=48'.

Like I mentioned before, the orignal design was by an engr. who left the firm. I never like the idea of planks spanning into the side of the beam. The one good thing I see in the detail is that for plank bearing, an inverted steel angle welded to the beam is being used. So in essence I have two small tubes with in the beam, which makes me feel better for the any twist issues.

I am going to ask:

1) The beam be braced until the installation of planks and repair of the top flange is done.
2) Cut the flange starting 1' from the end of beam.
3) The precaster to provide a detail of how he is going to have the steel fabricator re-weld the flange and I'll suggest use of a pre-welded backer rod.

In response to some of the questions: The beam is braced by planks on each side. And no this was no my design, the kid engineer did not put a lot of thought in to who this was going to get built.

Kaiser

 

[a2mfk]

What about redesigning the W30 as a composite section?

If the panels are hollow core, you could grout the ends to form a composite section with the beam, using a smaller W beam so you can bear the panels on top of the WF (with headed studs of course).

Or a concrete girder, with L's cut out of each side at the top to form a ledge for the panels?

Yep, someone did not think this one out as we all can see....

 

[kaisersoze]

@ a2mfk: Thats sounds like a neat idea, one I actually thought about, welding headed studs to the web BUT, I think the precaster would not like the idea and nor would he take any responsibility for any composite action. His planks are designed to be an independent system. In my opinion this option was way too out of the box .

Kaiser