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Discussion Starter · #1 ·
Ok so I know this is a forum for professionals and admittedly I am not one, but please keep reading. I am a student at Johns Hopkins and part of engineers without borders (google it for info). Our project is to help creating a weir and tank pump system to help provide clean water to the village of Chicorral Guatemala. Currently they must traverse a 100m ravine that is steep and danerous in order to get water from a stream. Whats worse is that the women and children usually end up getting the water because the men have to go work.
That said, I am part of the team that designed the foundation that will hold the top tnk (it weighs more than 6000kg). I have to write up construction plans and was wondering if you could critique them. Essentially we are creating a slab on grade foundation the is 1mx1mx.2m (3'x3'x8" more or less). From the slab 4 1m columns will portrude to be the corners of cinderblock structure (imainae four cinderblock walls making a sqaure except tha the corners are concrete). I Have attached a diagram of the structure

Also my design for the column forms are based on this:
tpub.com/content/construction/14043/css/14043_177.htm

My questions are:

1-Dos it matter how deep we di as long as we get rid of the topsoil?
2-Should i put sand down as a base layer if we dont have acces to mechanical compacting machines
3-Will my forms for the columns hold up?
4-How do I cure the columns?

please also look for problems in the construction plan
THANKS ALOT, you are really helping people out who need it because if we don't pass the tech inspection these people will have to wait longer for water

p.s. I know I sound like an idiot in that post, but don't judge me; I'm sick, tired, have a sprained wrist, and have been working all day on a Saturday haha.

View attachment Top Tank Construction Plan.doc

View attachment Compaction device A.doc

Text Technical drawing Line Floor plan Diagram
 

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Discussion Starter · #2 ·
oh and sorry for the small screenshot, word doc was too big to upload
i can email it if you want to see it
 

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I think if you are a student, that qualifies you as a professional, we just don't want homeowners asking questions on how to trim out their fireplace or whatever. I could be wrong, but the mods will tell you.

As far as how deep to dig, you really need to know the soil conditions for that. is it clay? organic silt?

I'm a little confused with your drawing, it could use some more dimensions and labeling. Are we talking meters or feet and inches? Are you building one slab with four columns? so a column in each corner? Or is it four separate slabs that size? A 3' x 3' base sounds small for a 13,000 lb water tank.
 

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Discussion Starter · #4 · (Edited)
All dimensions are in meters. And sorry I meant the slab is 3m x 3m x.2m.
As for soil conditions, I think I can find out.

edit: and it is one slab that has four columns protruding, the columns will be connected with cinderblocks/mortar. the inside of the box created by the cinderblock/4 columns will be filled with soil. Then we wille pour a lab of concrete on top of that (same l x w and it is 5 in thick)
 

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From what I gathered it is a slab on grade with 4 concrete columns coming out of it and CMU in between. This entire structure will become the tank.
In guatemala I would think there would be no danger of frost so depth would not be an issue just get down to undisturbed earth.
The real problem I have with this is the concrete block filling in between the columns and keeping the walls tied to the columns. This will require a continous joint at each column intersection. What will keep the CMU from failing at that joint from the water pressure on the inside.

Better yet would be to place a keyway in the slab with rebar vertically and horizontally and forming and pourng concrete walls with perhaps a pilaster or butress mid span on the longer walls.

IMHO as designed it would be a potential disaster.
 

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Discussion Starter · #7 ·
the tank sits on top of the structure
its a 6000L rotoplas tank
the vendors in gautemala are kind of shoddy so we never got an exact weight for the tank
so we assumed the tank weighed 15% of the water (6000L of water = 6000kg)
 

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Keep in mind that the water pressure is 2.3 psi per ft of verticle rise, so you will need continous reinforceing in order to resist that pressure.
 

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solar guy
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OK so you have a tank that is filled that weigh's 6900KG or about 15200 pounds for those of us who are metrically challenged

This is sitting on a base that is roughly 10'x10'

Why are you putting a continuous slab under it?
If you did a 2'x1' perimeter footing this would be plenty Here's why
You have approx 72 square feet of bearing on soil
If we assume a soil bearing capacity of 2000 pounds per square foot the perimeter footing alone is capable of supporting 154,000 pounds, or 4,000 pounds per lineal foot.
Lose the continuous slab and do a trench footing.
Lose the columns and build out of CMU place a pilaster at the mid point of each perimeter so the top elevation is about 12-16" below the top of the walls
Set a column in the center on a 4'x4' footing. 12-16" below the top of the walls
Fill the structure with soil don't worry too much about compaction. This is only used as a form for later.

When you pour your top slab form trenches in the earth down to the height of the pilasters set the appropriate amount of steel in the trenches and slab and pour the slab. The thickened portions become grade beams to support the slab and the tank

You were putting way too much thought and materials into this. considering the ultimate loads that may be incurred.
 

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solar guy
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Keep in mind that the water pressure is 2.3 psi per ft of verticle rise, so you will need continous reinforceing in order to resist that pressure.
The pressure of the water is of no consequence here. Water pressure is within the tank and we are not designing a tank, or are we?
The tank weight and size of the footprint of the tank however is.
 

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A few very preliminary thoughts.

Doesn't Guatemala have a fairly heavy annual rainfall? This needs to be taken into consideration in not only construction, but also in the site location, foundation depth and preparation, and the surrounding drainage and erosion protection plans.

Also, why are we constructing a separate base and tank situation? Have you considered a unified foundation/base/tank design? Much cheaper to build and maintain.

Think, too, about building a tank that is a cone shape. Smaller at the top than at the bottom by about 30%. This will lessen wall pressures, concentrate the total weight toward the bottom and the center, and greatly reduce the tendency for the tank to shift or topple.

Solid concrete construction could easily be lined to prevent contamination from the concrete... (spray application), could be relined periodically... and will totally eliminate the chance of metal tank corrosion or rust and composite material tank deterioration.

Since I am challenging the basic design, I won't bother to elaborate much more till you think this different concept over.

The point here is why purchase a separate tank at all? Build an all-in-one that cannot be damaged nor stolen, and will never deteriorate.
 

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solar guy
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A few very preliminary thoughts.

Doesn't Guatemala have a fairly heavy annual rainfall? This needs to be taken into consideration in not only construction, but also in the site location, foundation depth and preparation, and the surrounding drainage and erosion protection plans.

Also, why are we constructing a separate base and tank situation? Have you considered a unified foundation/base/tank design? Much cheaper to build and maintain.

Think, too, about building a tank that is a cone shape. Smaller at the top than at the bottom by about 30%. This will lessen wall pressures, concentrate the total weight toward the bottom and the center, and greatly reduce the tendency for the tank to shift or topple.

Solid concrete construction could easily be lined to prevent contamination from the concrete... (spray application), could be relined periodically... and will totally eliminate the chance of metal tank corrosion or rust and composite material tank deterioration.

Since I am challenging the basic design, I won't bother to elaborate much more till you think this different concept over.
Willie
I think this is a base supporting structure that a rotomolded tank will sit on. The OP is getting frustrating with not answering questions.
 

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Discussion Starter · #13 ·
tank design is not an issue, the tank is being purchased and we can only choose from a limited number of designs
I did not desgin the structure, this project has been goin on for a few yrs and the design was done before i came to jhu, so i do not know why the design is the way it is and it is too late to change the design. I just want to know if my construction plan is good. Also I have a few more specific questions:

1-When you cure the concrete via flooding, what are coomon ways to remove the water after curing?
2-The implementation will ahppen in two parts, one this winter and one this summer. If we leave 3 in of rebar sticking out of the top of each column for half a year will that lead to structural damage? What if we cap the rebar?

thanks again, his is really helpful
 

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Why I think it's good you are trying to get some info here, I think it would be more prudent to be getting advice from a local engineer. This is going to be built with local materials I would assume, and not from materials you are going to bring in. That being true the local materials and a local engineers familiarity with them and the building techniques is going to be very important. PSI hardness of the final structure is going to be based on this local information.

I've seen lots of 3rd world construction and most concrete work consists of bags of concrete mixed with on site screeded sand, the blocks are usually locally built also.
 

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Discussion Starter · #15 · (Edited)
OK so you have a tank that is filled that weigh's 6900KG or about 15200 pounds for those of us who are metrically challenged

This is sitting on a base that is roughly 10'x10'

Why are you putting a continuous slab under it?
If you did a 2'x1' perimeter footing this would be plenty Here's why
You have approx 72 square feet of bearing on soil
If we assume a soil bearing capacity of 2000 pounds per square foot the perimeter footing alone is capable of supporting 154,000 pounds, or 4,000 pounds per lineal foot.
Lose the continuous slab and do a trench footing.
Lose the columns and build out of CMU place a pilaster at the mid point of each perimeter so the top elevation is about 12-16" below the top of the walls
Set a column in the center on a 4'x4' footing. 12-16" below the top of the walls
Fill the structure with soil don't worry too much about compaction. This is only used as a form for later.

When you pour your top slab form trenches in the earth down to the height of the pilasters set the appropriate amount of steel in the trenches and slab and pour the slab. The thickened portions become grade beams to support the slab and the tank

You were putting way too much thought and materials into this. considering the ultimate loads that may be incurred.
I have difficulty understanding this as I'm not well versed in much of the technical language you've used; so if I totally misunderstand something, sorry. I will consider adding footings to the design as they seem useful. The point of the CMU unit with the top slab on top is to elevate the tank since it will gravity feed to a tap. So if you're suggesting that we put the tank on just the bottom slab with footings then we can't do that because it won't feed water to the tap. And as for the pilaster and central column design, well, I don't get what you're saying like I can't picture it. Sorry again, I'm just not a seasoned construction expert like yall.
 

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Discussion Starter · #16 ·
Why I think it's good you are trying to get some info here, I think it would be more prudent to be getting advice from a local engineer. This is going to be built with local materials I would assume, and not from materials you are going to bring in. That being true the local materials and a local engineers familiarity with them and the building techniques is going to be very important. PSI hardness of the final structure is going to be based on this local information.

I've seen lots of 3rd world construction and most concrete work consists of bags of concrete mixed with on site screeded sand, the blocks are usually locally built also.
We do check with local engineers and the community we are doing the project for is comprised of many masons, but it is difficult to communicate with them in a timely manner as they live in a remote village.
 

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We do check with local engineers and the community we are doing the project for is comprised of many masons, but it is difficult to communicate with them in a timely manner as they live in a remote village.
If this is a remote village I find it hard to understand how there are local engineers there. A mason is not an engineer.

I would think you should be making contact with an engineer in Guatemala City, or a student in one of the civil engineering universities in Guatemala City?

Have you heard of Engineers without borders USA?

Also, why does this need to be so elevated? What is the tap design that requires it to be so high off the ground? Is this going to be plumbed to something else or is it just a valve? I'm confused at the height requirement. A Rotoplast tank sitting on the ground would work under normal circumstances.

Are you familar with this?

Water for the world
 

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If this is a remote village I find it had to understand how there are local engineers there. A mason is not an engineer.

I would think you should be making contact with an engineer in Guatemala City, or a student in one of the civil engineering universities in Guatemala City?

Have you heard of Engineers without borders USA?

Also, why does this need to be so elevated? What is the tap design that requires it to be so high off the ground? Is this going to be plumbed to something else or is it just a valve? I'm confused at the height requirement. A Rotoplast tank sitting on the ground would work under normal circumstances.

Are you familar with this?

Water for the world
What say!?!? A solid concrete tank... an all-in-one piece of construction? Where have I heard that before? :whistling
 
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I throw in on this.

Your concern seems to be gravity feed from the outlet of this tank.

The tank could be put on a slab on grade with steel reinforcement, at the high point on the site, the delivery point can be 10 or 20 feet away (down slope) at a lower area, or an area can be excavated and 1 short wall can be constructed as a retaining wall, delivery can be at that point.

This can be done with way less material, labor and money than what has been proposed.

Depending upon the requirements of the tank manufacturer, you might not even need a slab to set this on, just a level solid surface with adequate drainage.
 

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Discussion Starter · #20 ·
If this is a remote village I find it had to understand how there are local engineers there. A mason is not an engineer.

I would think you should be making contact with an engineer in Guatemala City, or a student in one of the civil engineering universities in Guatemala City?

Have you heard of Engineers without borders USA?

Also, why does this need to be so elevated? What is the tap design that requires it to be so high off the ground? Is this going to be plumbed to something else or is it just a valve? I'm confused at the height requirement. A Rotoplast tank sitting on the ground would work under normal circumstances.

Are you familar with this?

[/quote]

We are currently trying to get professional partners from Uni's in Guatemala City. I am not sure if the engineers the team spoke with live in the town, but they have done construction in the town before. I am in the JHU chapter of Engineers without borders. The tap is designed quite simply, a valve that allows for the flow of water is mounted in cement. The tap is gravity fed as we are using the solar panel energy to pump the water up from ravine, that is why the tank must be elevated above the tap (the whole structure on which the tank will sit is 1m high). The tap must deliver water even when the tank is near empty (as will be the case at night since water is only pumped during the day). I'll look into the link when I have some time, kinda busy with school at the moment.
 
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