Water reservoir-straight vs zigzag wall
Water reservoir-straight vs zigzag wall
(OP)
Dear all,
I am a mechanical engineer but it doesn't stop me of nailing some civil concepts!
Dealing with a 50000 m3 concrete water reservoir, due to land limitation, consultant civil department has submitted the reservoir plan like the following schematic sketch (blue color is the proposed plan):

Here's my question: why not using a straight wall (such as alternative 1 or 2) instead of the zigzag south walls? Any design or construction consideration? wall height is around 6 meter.
Thank you all in advance.
I am a mechanical engineer but it doesn't stop me of nailing some civil concepts!
Dealing with a 50000 m3 concrete water reservoir, due to land limitation, consultant civil department has submitted the reservoir plan like the following schematic sketch (blue color is the proposed plan):

Here's my question: why not using a straight wall (such as alternative 1 or 2) instead of the zigzag south walls? Any design or construction consideration? wall height is around 6 meter.
Thank you all in advance.






RE: Water reservoir-straight vs zigzag wall
RE: Water reservoir-straight vs zigzag wall
With a water reservoir, you need to keep cracking minimized and stress risers avoided.
RE: Water reservoir-straight vs zigzag wall
RE: Water reservoir-straight vs zigzag wall
Using the term "ZigZag", maybe the original designer .....
No, couldn't be.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Water reservoir-straight vs zigzag wall
Thank you all for the comments and thoughts so far.
@ishvaaag: Considering the other elements of the project, I am sure that the visual impact is not of concern (or even a thought) here. However, a straight wall seems nicer to my eye from the horizon level or even a vertical level from an airplane! :)
@JAE: Good point!
@cvg: Yes, it's a vertical wall reservoir. Due to sloped topography, the walls are almost buried to semi buried. However the south wall has almost a constant height of 2-3 meter above the ground.
My concern is the less construction material and time of the straight alternative. Still wondering what was in the mind of the designer for the south wall. A straight wall is only 2 or 3 meter longer than 100 m north wall. Whatever the benefit for the south wall, why not make the north one zigzag?!
Still looking for your comments before going to ask the same question from the designer in a meeting.
RE: Water reservoir-straight vs zigzag wall
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Water reservoir-straight vs zigzag wall
RE: Water reservoir-straight vs zigzag wall
I like a straight wall configuration much better. I'd put in contraction joints near the corners and every 90 ft. or so. In between them I'd put construction joints every 30 ft.
A six meter cantilever wall is a bit much. Footings and reinforcing will be heavy. I'd prefer to slope the floor at about 2 horizontal to 1 vertical until the wall height is about 4 meters or less.
RE: Water reservoir-straight vs zigzag wall
RE: Water reservoir-straight vs zigzag wall
Another tip I try to remember is to add a few horizontal bars at the slab wall joint. This also reduces shrinkage cracks at that joint.
RE: Water reservoir-straight vs zigzag wall
RE: Water reservoir-straight vs zigzag wall
RE: Water reservoir-straight vs zigzag wall
Hopefully, I can ask the question in a meeting next week. Get back here if they give something worthy.
RE: Water reservoir-straight vs zigzag wall
Looking to the drawings more, I speculate that the zigzag wall is because of having paneled roof on the top. This means that the designer has put the south wall this way in order to use the same panels between each column to cover the roof.
The length between the columns is 5 meter and the panels' length is 4.6 meter. So instead of the inclined wall (which means different length for the last panels that are resting on the inclined wall), zigzag wall is used.
Now the question to dear structural experts: Does it justify the added length (around 7 meter) of a wall with 6 meter height? also the added stresses on the 90 degree corner and more details and bars there?
Is there a method that enables building the roof close to the proposed inclined south wall (alternative 1 or 2) and then make the connection to the paneled roof?
I have to sit at the meeting tomorrow and your help is appreciated.
RE: Water reservoir-straight vs zigzag wall
RE: Water reservoir-straight vs zigzag wall
RE: Water reservoir-straight vs zigzag wall
Regarding your comment "Actually, we use contraction joints in straight walls all the time. Stop the horizontal reinforcing and use 9" centerbulb waterstop" -
Do you also use a deeply grooved vertical joint with post-applied Sikaflex in conjunction with the movement joint, and align this movement joint with a construction joint?
I avoid movement joints in environmental structures at all costs, but you can't for straight runs longer than 100'.
More importantly, how do you post a picture in the body of the text like waterpipe did (and not as an attachment)? Sweet.
RE: Water reservoir-straight vs zigzag wall
see below for posting images
http://www.tipmaster.com/includes/tgmlinfo.cfm
RE: Water reservoir-straight vs zigzag wall
And yes, there is a groove and caulking. We don't expect a wide crack, but just in case, we put in 9 inch centerbulb waterstop.
If the reservoir is large enough (>200 ft.) we put an expansion joint in the middle somewhere.
We do a lot of these type structures and have worked a lot of this out through trial and error. That and stealing from the competition.
RE: Water reservoir-straight vs zigzag wall
RE: Water reservoir-straight vs zigzag wall
I had a meeting with the designer firm at the construction site. As soon as I shot the question, the senior structural engineer said: "It is a valid concern and there is no explanation for the inclined wall. Few custom panels are nothing compared to the added complexity and materials. I had the same question when I came in ... blah blah blah. BUT the wall pouring has started!".
Well, I take it as an example where there's no "thinking" brain behind a project and planning. A "desk engineer" designer plus no supervisory control definitely lead to these kind of blunders.
I am sorry, but this time it was you structural colleagues! :)
Best regards
waterpipe
Mechanical Eng.