Steel frame building precast planks

[oneintheeye]

In design of the internal steel beams do you consider the condition at ULS of bending and torsion induced by the bay on one side of the beam being loaded and the other bay not (no live load)?

 

[mtu1972]

I do now - after a construction related accident where precast plank were placed full length along one side of a WF beam before the other side was placed.

The beam failed in torsion under partial DL only. Fortunately no on was hurt.

As we don't usually get into means and methods, this was not originally a concern of mine. A design review showed that my beam had plenty of design capacity, once all of the plank were in place, laterally braced through the plank welds, etc.

For the remainder of that project, we asked the contractor to place the plank on each side of the beam, one after the other, so as to keep the load balanced.

I now check unbalanced loads or add additonal steel framing to insure adequate lateral bracing of the support beams.

gjc

 

[DaveAtkins]

I agree with mtu1972. I wouldn't worry about pattern live load, but I would design for unbalanced load during construction (especially if the planks don't sit on top of the beam, but on ledge angles on the sides of the beam).

DaveAtkins

 

[oneintheeye]

dave that is exactly my condition. Also I have bays over 6.5m and they are not equal. Pattern loading is governing the beam size. Looking at previous designs I don't believe this was taken into account previously. The construction condidion I have checked also.

 

[DaveAtkins]

Sounds like you are looking at it correctly.

DaveAtkins

 

[msquared48]

Skip loading has been around for years and still appropriate.

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

 

[countervail]

Dave

That's exactly as most design guidance I have seen tells you to do it, sometimes it doesn't get considered just because it hasn't been considered before, SCI (UK) guidance is to check it.