Cantilever retaining wall vs. counterfort retaining wall 1

[ars001]

I've been requested to design a salt storage shed will a 10'-0" tall concrete retaining wall. The stucture sits on top of the retaining wall. The retaining wall shall resist the forces for the salt/sand material and also forces from equipment. Any ideas on what sort of lateral loads shall be used for the loaders loading the material? It has been suggested to design the walls with counterforts or buttresses. What are the advantages of butresses? With butresses the concrete wall is designed to span horizontally between butresses. Is this correct?

Thanks for the help.

 

[csd72]

It is much more expensive with build with buttresses. This is why most walls are designed as cantilever these days.

csd

 

[bridgebuster]

Try this thread:

http://www.eng-tips.com/viewthread.cfm?qid=166662

 

[msquared48]

It is true that with butresses, the wall steel spans horizontally, and the increases with the depth of burial.

It is also true regarding the higher cost of a butressed wall due to the extra forming and extra time involved in the construction of the wall.

Mike McCann
McCann Engineering

 

[BarryEng]

I have designed cantilever, buttress & counterfort walls up to 10 m depth.

Checking several designs (some years ago), the optimum maximum height for a cantilever wall was about 6 m (about 20 ft). After that, counterfort or buttresses.

Counterfort if you require an open area (for a spillway with water, or for a loading area where you require a clear floor with no obstructions).

Buttress is usually cheaper (fins are in compression, not tension) for the same height compared with counterfort, however, a counterfort has the additional earth load on the the heel slab for overturning efficiency.

You really have to do the sums for your local conditions (local construction costs, type of backfill, cost of materials etc etc).

As far as design is concerned (for the front wall of counterfort & buttress walls), use 'Moments & Reactions for Rectangular Plates' a water resources technical publication 27.

Have a look at my answer to flat plate design in thread181-27567 for more info (for a rectangular tank).

As far as loads are concerned, why not design the wall for an extra 0.5 m or 1 m of fill (also checking on angle of repose of the fill material etc) to take care of construction loads? This method is acceptable (& relatively easy), in some bridge codes (abutment wall design).

 

[BarryEng]

Sorry about that - I just read bridgebuster's answer above (I should have done that first, before starting to write).
That would have saved me some work.
Check that thread for finding the detailed info on rectangular plate design

 

[WBUW]

To accomodate the loaders I would consider using a construction type surcharge (I assume we are talking about loaders running around the structure) I think this is typically 80 psf. I don't have my IBC on me though.