Grating Load Tributory Areas

[Leftwow]

Guys,

I have a hard time imagining that the tributary area for grating supported on four sides, is actually supported on two depending on the direction of the major grating bars. It seems like the grating bars welded together would be fixed. Even if this is so, I don't know how you could choose which side the grating would run. After all, it's still sitting on all four beams. What are your opinions on this?

 

[KootK]

Sure, there'll be some two way action happening. That said, your spanning bars are flexurally continuous for Z x Fy and your distribution bars are only as good as the welds. I'd design the intended supports to take one way load and, perhaps, design the unintended supports to take a trib based on two-way action. Actually, that's a lie. Out here in profit land, I'd just do one way and and keep on trucking.

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.

 

[Bendog01]

The bearing bars carry the floor load and span from one beam to the next. The cross bars provide lateral support for the bearing bars and do not carry any floor load. Therefore the grating is supported on two sides.

 

[jayrod12]

One way span. those cross bars just fold over if put under any real bending loading.

 

[Leftwow]

Ok but for live load you still have to distribute it based on standard two way tributary area right?

 

[MotorCity]

It will span in the stiffer direction, so if you have grating w/ rectangular openings it will span parallel to the long side of the rectangle. If your grating as square openings and the grating covers a rectangular area, the grating will span the short direction of the grating area.
That's the quick and easy way, but if you are really ambitious you could create an FEA model which more than likely is not justifiable.

 

[JStephen]

Note that for rating the grating for loads, the manufacturers assume 1-way action only.

 

[SwinnyGG]

Out here in profit land

This might be my favorite post of yours ever. And that's an achievement, because your posts are always among the best/most helpful in whichever thread contains them.

 

[jayrod12]

Ok but for live load you still have to distribute it based on standard two way tributary area right?

Why do you think this? If the cross bars have zero bending strength, how you do see the load going two directions?

On your drawings indicate your intended span direction, and then design your beams accordingly.

 

[Leftwow]

Well a guy could be standing on top of a beam, that is parallel to the direction of the main bars, all the live load would be transferred to that particular beam, or construction workers walk on the beams before the grating is lain down

 

[KootK]

@jgKRI: thank you for the kind words. I'm out here in profit land digi-blushing.

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.

 

[jayrod12]

Your grating can't be spanning anything that overly significant. You do need to provide a beam at the edge of the grating, but I'd put my money on something ridiculously small being able to support a 350, or 400 lbs load over the same span as your grating.

 

[Leftwow]

lol same rebuttal my boss gave be jayrod, I'll just take your word for it

 

[jayrod12]

I liken it to say a roof edge angle. A 3x3x1/4" angle regularly spans 6 ft with workers walking all over it during installation. Nothing bad ever seems to happen.