Need advice to design reservoir
Need advice to design reservoir
(OP)
Hi,
I have to design a rectangular concrete reservoir for containing sugar cane molasses/syrup (density=1500 Kg/m3).
Dimensions: length=100m, width=35m, depth=6m
Some of the project constraints are:

With that option out of consideration I have to fall back to other alternatives that contemplate vertical walls made of precast panels. Basically I'll have to stick with variations of the concepts depicted in Pics. #2a, #2b and #3.
There's also another alternative with a more elaborate panel with heel and toe, like the one manufactured by the Italian company Paver. See this page and the PDF here . Their products, however, are meant for grain storage.
I'd rather think of this structure not as a plain old rectangular tank, but as a long retaining wall whose worst load case is when the reservoir is empty. Prevention of wall overturning, translation and rotation are my biggest concerns (maybe the internal columns/beams for supporting the TT roof panels could serve as struts to prevent OT/trans./rot.?)
To sum up, I'm in the early stages of self brainstorming on this subject and, based on the experience of the members of this forum, would like to know opinions on the most efficient, safe and economic design I should focus on going forward, satisfying the constraints set above.
How would you tackle the desing of a reservoir like this one?.
Thanks.
I have to design a rectangular concrete reservoir for containing sugar cane molasses/syrup (density=1500 Kg/m3).
Dimensions: length=100m, width=35m, depth=6m
Some of the project constraints are:
- The walls must be of precast reinforced concrete panels. (no prestressing or post-tensioning, except as a very, very last resort)
- The reservoir can be fully or partially underground (see Pics. #2a-#2b and #3)



- The floor will be of poured concrete.
- The whole structure will be roofed.
- Walls and floor must be watertight.
- The jobsite is in a moderate seismic zone.
- Several smaller reservoirs instead of a huge one is not an option.
- Unlimited crane availability.

With that option out of consideration I have to fall back to other alternatives that contemplate vertical walls made of precast panels. Basically I'll have to stick with variations of the concepts depicted in Pics. #2a, #2b and #3.
There's also another alternative with a more elaborate panel with heel and toe, like the one manufactured by the Italian company Paver. See this page and the PDF here . Their products, however, are meant for grain storage.
I'd rather think of this structure not as a plain old rectangular tank, but as a long retaining wall whose worst load case is when the reservoir is empty. Prevention of wall overturning, translation and rotation are my biggest concerns (maybe the internal columns/beams for supporting the TT roof panels could serve as struts to prevent OT/trans./rot.?)
To sum up, I'm in the early stages of self brainstorming on this subject and, based on the experience of the members of this forum, would like to know opinions on the most efficient, safe and economic design I should focus on going forward, satisfying the constraints set above.
How would you tackle the desing of a reservoir like this one?.
Thanks.






RE: Need advice to design reservoir
RE: Need advice to design reservoir
How will you approach waterproofing a pre-cast structure?
RE: Need advice to design reservoir
RE: Need advice to design reservoir
RE: Need advice to design reservoir
Roof material:
Prestressed TT's
Roof load: Self weight.
Roof support: internal reinf. concrete columns and beams
@cvg:
How do I assemble the panels on the sloping ground?
Non-shrinking cement grout plus polyurethane sealant in the joints.
@graybeach
No, the water table is not an issue.
@civilperson
Advice taken!
Thanks.
RE: Need advice to design reservoir
As someone pointed out, you have to consider hydrostatic uplift when the tank is empty.
RE: Need advice to design reservoir
For the tank design, I would recommend the PCA Rectangular Concrete Tanks, 5th Ed. book. It is very useful to understand the "behind the scenes" workings of a FEM model and helps in determining the loading. The PCA also has a "Design of Liquid-Containing Concrete Structures for Earthquake Forces" that may help in the seismic design.
I don't know if this is the design helps you were looking for, but fyi.
RE: Need advice to design reservoir
First, I would ask why so many constraints and are they all really necessary ?
good luck
RE: Need advice to design reservoir
RE: Need advice to design reservoir
please start a new thread.
RE: Need advice to design reservoir
RE: Need advice to design reservoir
Maybe someone has already pointed out before, without concerns of water, tongue & groove pannels maybe benefitial in many aspects, though could be little bit expensive to produce.
RE: Need advice to design reservoir
This is an enormous molasses tank, larger than I have heard of, and deserves consultation with an engineer with experience in the sugar industry.
I would think for a tank of this size you would want to compartmentalize it for maintenance.
RE: Need advice to design reservoir
i.e. dig a trench, fill up with bentonite clay then drop in reinforcement and fill with concrete.
No health and safety issues with regards to shoring e.t.c.
Make it as deep as it needs to be to cantilever.
RE: Need advice to design reservoir
Don't forget "wind swept rain" from eaves back to retaining wall, then percolating down the retaining wall.
May be surprising the speed of damage to interior sealing from acidity at hydraulic head.
At 74th year working on IR-One PhD from UHK - - -
RE: Need advice to design reservoir
But before I proceed with the design, I'll appreciate some guidance to clarify a few doubts:


Thanks.Is it correct to decompose the at-rest earth pressure σh in two triangular in-plane and normal distributed forces? (see the red, pink and green arrows respectively on Pic. #1b) .....Do I have soil pressures at all?
When the reservoir is full (or empty), is it correct to analyze a strip of unit width of the structure as a beam on an elastic foundation as shown on Pic. #1c?
The concrete thickness and reinforcing steel of slabs on grade are chosen mostly from engineering judgement based on loads and suitability of the subbase and deeper strata, and 999 out of 1000 times it just works. For this design to be approved by the client I must attach the calcs. So my question is, what is the most suitable software package for analyzing this huge soil-supported concrete slab with inclined sides, including dynamic analysis from seismic effects? What is the learning curve like? This job is in seismic Zone 3. See next item.
How do seismic provisions affect the design? With regard to analysis, what things change besides the addition of statically-equivalent loads from shear at the base and hydrodynamic forces from the stored liquid? What's the aim of seismic design in connection with storage reservoirs? Add ductility or strength? I have ACI's 350.3-06 Seismic Design of Liquid-Containing Concrete Structures and Commentary but it's not an easy read and it doesn't have any step-by-step worked examples.
RE: Need advice to design reservoir
2. For your model, consult a geotech eng, or senior structural engineer, to define proper spring constants. The grade beams at the base are much stiffer than the slab, this will complicate the issue. I will try a model without beams to start with, that might result in thicker walls and base, but will simplify the analysis/design, and help in uplift case (heavier). If you intend to use computer program, why not model the entire reservoir, or a strip, as is (with tilting walls)?
3. Many commercial programs suit your needs, I will say STAADPRO and RISA3D are two easier programs to handle, the learning time depends on your familiarity with structural analysis programs.
4. The success of your project is pending heavily on understanding of dynamic soil-structure interaction, which, unfortunately, is not well covered by most, if not all, of the codes. As pointed out in (2)- you need talk to competent persons about special features such as effects of soil dynamic as well as fluid-dynamic. Also the potential of liquification (if the site has deep sand layer below) and slope stability needs to be investigated/thought of, for both static and earthquake cases.
The above represent a personal opinion. good luck.
RE: Need advice to design reservoir
Placing granular fill under the walls would be easier if the slope was a bit shallower, say at the natural angle of repose of the gravel base course below the wall.
If there is no hydrostatic head, at-rest pressure seems to me to be overly conservative for the walls.
What supports the upper grade beam? Are you contemplating piles spaced at intervals under the beam? Will there also be a system of piles or footings under the interior columns to support the concrete roof?
What is the function of the lower grade beam?
Best regards,
BA