Piles on Steel Pipe 1

[burnhakp]

I have a horizontal steel pipe burried underneath a box culvert with two wood piles resting between the box culvert and the 60" dia. steel pipe. I have computed the loads and determined that each pile applies 10.6 kips on the pipe. The two piles are spaced 14 ft c/c and I am assuming that the piles rest directly on the top of the pipe. How can I determine the required thickness of the pipe? I attempted to check with flexure, but the resulting thickness was too small and did not make sense.

 

[BAretired]

Your description is not clear. Provide a sketch.

BA

 

[nuche1973]

I'm gonna take a swing at this: you have a box culvert being suported by two pairs of wood piles, with each pair bearing on a horizontal steel pipe. So, your FBD would show a Load from the culvert, split to the pair of wood piles, split to the pipe. Essentially the pipe carries P/4 on each end. (I am assuming the pipe is parallel to the culvert.

I see several factors involved: bending in the pipe, soil bearing on the pipe, affect of fill material between the pipe and the culvert, affect of water, lateral load on the piles, uplift on the culvert.

One important question is: are the piles bearing at the end of the pipe? Or is there a length pipe beyond the piles. This changes your shear and momemt diagram,which will determine your size.

Am I on target? It is hard to visualize with-out a sketch.

There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.

 

[burnhakp]

Yes you are correct. The pipe extends beyond the length of the box culvert. Here is a sketch

http://i56.tinypic.com/11tn6mg.jpg

From surface to bottom of pipe is 20 feet, top 4 is OH @ 110 PCF , bottom 16 is SW/ML/PT @ 115 PCF. I assumed culvert was filled with water.

 

[nuche1973]

Is the pipe filled with anything? Could you fill it with concrete and make it a composite section?

There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.

 

[burnhakp]

Its a conveyance pipe for a CSO project.

 

[BAretired]

The solution to that problem is not simple.

Could you provide four piles, two each side of the pipe so that the loads are supported by the soil without stressing the pipe?

BA

 

[burnhakp]

Im working on modeling the forces and yield stress of the pipe in Phase2 by rocscience. It looks like the pipe wont need to be that thick to carry the load.

The two wooden piles are 8 feet long into the sketchy that I drew. Its what the client wants to go with.

 

[BAretired]

What the client wants to go with is neither here nor there. If anything goes wrong, it will be your neck in the sling. Personally, I would not even consider doing it, but if you want to do it, there is a similar case addressed in "Theory of Plates and Shells" by Timoshenko and Woinowsky-Krieger, Second Edition, Article 120, page 501. It is not exactly the same as it considers two equal and opposite concentrated loads at opposite ends of a diameter of a cylindrical shell which I think is more critical than your case.

Good luck...you'll need it.

BA

 

[nuche1973]

My initial assumption was that the pipe was parallel, but from the sketch, it looks perpendicular. How long is the culvert? Can you straddle the pipe? Or even lengthen the culver to straddle the pipe?

There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.

 

[BAretired]

Straddling the pipe is by far the most sensible solution.

BA