Design concrete panel lagging as simple beam or as a slab?

[Bayek949]

First time being asked to design precast concrete lagging panel for a permanent soldier beam & lagging retaining wall.

Span between soldier beams is 8' (so length of concrete lagging would be a little less than that, but call it 8' span for simplicity). Typical detail from state's bridge design sheets is 4' height of panel, 9" minimum thickness; so 32 SF area (pg. 4 of below URL, Section E-E is the typical detail).

https://www.dot.state.pa.us/public/Bureaus/BOPD/Bridge/2014/bd/bd626m.pdf

Question: I was told to design like a simple beam, with a lb/ft load of the retained earth. But if I know the square footage, could I design it like a slab, and apply the earth pressure to the 32 SF?

Does anyone know any online FHWA/state department guidance, or design examples for this?

Thanks all.

 

[jayrod12]

I can't imagine the design would change that significantly. What would you expect changes considering it one way or the other?

 

[dhengr]

Bayek949:
Isn’t a one way slab essentially designed as a 1’ wide strip, as a 1’ wide beam, of such-n-such depth and span? Yours is 4’ wide and at least 9” deep/thick, and spans 8’. You might consider a new design every course or every couple courses, as a function of the decreasing soils pressures.

 

[Ron]

It will act as a simple beam and as JR12 notes, there won't be that much difference. The simple beam approach will likely be slightly more conservative.
In my opinion, it will behave more as a beam than a slab. There will not likely be any two-way action.

I have used hollow core panels as lagging for retaining walls. Works great.

 

[BridgeSmith]

I would say design as a simple span beam.

For simplicity, I recommend designing for the soil pressure at the bottom of each panel - by the time you're deep enough for the pressure to be significant, it doesn't change much from the top to bottom of a panel.

 

[PEinc]

How high is your wall? Is it a top-down construction wall or will you be placing fill behind the lagging after it is set? Precast concrete lagging can be very problematic, especially if the wall needs tieback anchors or top-down construction. This topic has been discussed several times in the Earth Retention Engineering forum.

P.S. It is not easy to get a permanent, soldier beam wall design approved by PennDOT's Central Office. Been there, done that. Unless your design is extremely conservative, including redundancy for tieback anchors, it could many months for approval (my experience and experience of others), especially if you need tieback anchors.

http://www.PeirceEngineering.com