Concrete Rectangular plates in soils

[structbear]

I understand that the Bureau of Reclamation publishes many design tables for fixed end moments and reactions for concrete plates bearing in soils such for wells and access manholes?

Where can I find this?

I have been using the tables published in Roarks and those by the PCA for tanks but find them too simplistic for soil loading I am running into or to span under roadways.

Also, is there a computer program widely used and where can I find it.

Thanks

 

[Focht3]

What are you designing? Where?



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[structbear]

I have run into several projects for a pipe manufacturer that where the manhole is cast out of concrete that are about 102 " in diameter that extend below grade 16 to 20 feet deep. These manhole have access panels or sump pits of smaller diameter typically not centered in the slab. The governing agency has required calculations for the top and bottom slabs and instead of a simplistic analysis, I heard about these tables published by the bureau of Reclamation. Also if there is a reasonably inexpensive program, I would like to know about that.

Sure simplistic is fine and conservative, but if many of these are cast, a more exact analysis would be economical.

 

[Focht3]

A 9.5 ft diameter manhole 16 to 20 ft deep is pretty damn big; are you dealing with some kind of lateral load? I'm having a hard time visualizing the loading condition, so I can't figure out what table you need (or if it exists.)

Please help me, so I can try to help you -



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[structbear]

No the lateral load is taketn through the pipe.

I have a 96" vertical pipe starting at grade and extending downward 20 feet. This pipe alows access down to horizontally placed pipe that ties perpendicular into this pipe at some depth to allow for cleanout, maintenance etc, This is very similar to a cylindrical tank or water reservoir. The top slab for this pipe is buried a couple of feet with a 24" diameter mamhole at grade in a roadway that is covered with a steel plate. This top slab must support a wheel load from a truck and span to the perimeter of the pipe. The bottom slb id designed with the idea that the pipe or tank is empty without water and must resist the upward pressure due to bearing at this depth.

The upper slab can be considered pinned at the perimeter or fixed. The lower slab can also be designed the same way dependining if fixity is acounter for and how the lower slam is cast. This lower slab is also penetrated by a smaller diameter opening and even lower slab to atlow for a clean out, wet well, or pump.

What I am lookimg for are design tables for flat plates that account for these conditions similat to those published in Roarkes Formulas for stresses and strains to determine positive and negative moments (at the perimeter for fixed conditions) and I heard that the Bureau of Reclamation publishes such tables.

Thanks

 

[cap4000]

You have me also confused about no lateral load?? Isn't their backfill surrounding this pipe down 20ft?? I would suggest this slab at the base be designed perhaps like a "MAT" Foundation. As for stresses developed there, engineers Braja Das, H.M Westergaard, Newmark,and Boussineq are excellent resources.I hope this at least points you in the right direction.Get different Engineers opinons. Good Luck!!

 

[structbear]

Backfill applys a load at the perimeter of the pipe in all directions and creates a radial compressive load and shear load which can be designed per AASHTO