Design of pile strip footing 3

[mte12]

I'm not familiar with design of piled strip footings.
Is there a reference you recommend as a guide.

Unsure if the continuous beam is supposed to allow for support from ground, or span between piles.
I don't have the geotechnical information, and presume insitu ground will be swapped out with sand fill locally.

 

[hokie66]

I call them grade beams, and design them to span between piles. After all, if the ground could support the loads, you wouldn't need piles.

 

[mte12]

Thanks for advising.
Reason I asked is that a while ago, I got the impression that rails (for trains) may have been designed as: Supported on sleepers, in combination with the ground.

 

[hokie66]

Unrelated. Sleepers (cross ties) are supported on the ground, and the rails are supported by the sleepers. The infill below the rails, between the sleepers, is called ballast, and just assists in keeping the sleepers aligned and resisting forces parallel to the rails.

 

[le99]

For a gantry crane track, you need something rigid to span between piles, the soil below is usually ignored.

 

[mte12]

Great, thanks for confirming.

 

[BridgeSmith]

Theoretically, you could use the soil under the beam, but you'd need to do something like a strain compatibility analysis to determine how the load is split between the soil and the piles. After considerable effort, you'd discover that the soil contribution is so minor (due to the support provided by the piles to be so much stiffer) it wasn't worth the effort. That's why it's typically ignored.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[mte12]

OK thanks for confirming.