Design of concrete structure underwater 2

[VVang]

Hello, does anyone have tips or advice on how to design a concrete structure that will be underwater? A contractor provided a 12" thick structure with #4 at 16 o/c (I don't think #4 at 16o/c for a 12" slab meets the minimum required steel). I need to verify that this will work but I have never done concrete analysis for a structure underwater and would like some tips or guidance. Can I have water load applied on both sides of the concrete for my analysis, essentially canceling any moment loads since they will be the same on both sides of the wall? Would concrete crushing be a more critical aspect instead of steel yielding? Any advice or input will be greatly appreciated, thank you.

 

[jayrod12]

What's the application? Will there always be matching water levels on each side, or is there a chance where one side has full water and the other doesn't?

Is it intending on retaining water? If so you may want to look into the tank standards for guidance.

 

[VVang]

One side will be water, the other side will be saturated soil. the intention of the structure is to prevent erosion of the soil during pumping/backwash which will in turn prevent anything from bring sucked into the pump. There will never be a case where the water side is empty. I am thinking of designing this as a normal concrete structure with all the extra loads applied. I just want to know if there's any tips to consider or if there's a different method for analysis.

 

[BridgeSmith]

There are some construction requirements if the concrete will be poured underwater. (The tremie tube has to be in the concrete a certain distance, etc.) There may be some different (larger) cover requirements for the reinforcing.

Saturated soil will produce a larger pressure on the wall than water, so there will be moment on the wall, even if the water level is the same as level of the saturated soil.

Our design spec (AASHTO) would require reinforcing on both faces for a 12" thick wall.

 

[JedClampett]

We always design for the two cases of:
[ul]
[li]Water on one side, no soil on the other and[/li]
[li]Soil on one side and no water on the other side.[/li]
[/ul]
They might excavate the soil or bulkhead off the water.

 

[HTURKAK]

I do not think also .. I would like to see around #6 at 10 o/c ( just acc. to past experience )


In this case, the structure would be constructed in water (with tremie etc). If dewatering will be carried out during construction, bouyancy could be problem.

Will you provide some details showing the str. with dimensions?



According to the grace of God which is given
unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. . . .
I Corinthians 3:10

 

[CrabbyT]

There will never be a case where the water side is empty.

Never say never. What about immediately after construction? What if they need to do maintenance on whatever it is that you're designing, and what if maintenance requires emptying the water out?

You should design it like JedClampett suggested.

Also, #4's @ 16" isn't adequate, even for min. temp/shrinkage steel.