Concrete submarine

[wellmer]

Originally Posted by MikeJohns

1)... what you call phobic questions of mine, are actually very reasonable and deserve a reply...

2)...You also have the possibility of improving your design with sensible discourse.

3) This is partly my field of expertise and it seems plausible from your posts that you have some concerning gaps in your knowledge....

4)...It appears that your approach is not so much an engineering approach as one of building and trial...

5)... if you are then unaware of some of the pitfalls and refuse to consider significant safety issues ...


6) Any engineer would expect to be asked these sorts of questions in any peer discussion and at a very pre-cursory level without taking umbrage.

7)You are the engineer of this proposed vessel and you could respond with your consideration of the issues addressed with clarity and sensible intelligence.

8)You are posting on a boat design forum in a design discussion thread. What do you expect ?

9)...I really wanted to see how well you had considered them. Apparently you haven’t.

10)...scenario that any submersible operator is trained for.

11)...Consider an uncontrolled descent... need to be able to gain buoyancy at a rate faster than you are losing it...

12)...loss of many small submersibles over the last 60 years and many deaths...

13)...to vent the ballast water ?

14)...Small subs are very limited in the gear they can carry and the redundancy they can afford.

15)...However of all the systems aboard the ability to emergency surface is number one.

16)... fixed ballast : I’ll propose that there should be at at least 2 ways of dropping it.

17)... automatic hydrostatic device ...

18) ... through hull rotating shaft... F

1) I give you that when you part from the ground that the military submarine ambient as the ground we are talking here - my problem is - my sub vision is not a "civil version of a military submarine". - It is a thing completely apart. Just to give a example: the question "what helmet do you use?" might appear completely decent and logical in a military diving ambient - while it would bring you a in a scuba resort. So to start with details you should accept that there are very different brands of "being submerged" apart from military subs and mine definitively is one. So most of the questions type "how do you reproduce the systems of our military subs" have just the answer - i do not reproduce the systems of military subs - i do a different thing.

2) I am always open to design improvements - in fact keep the design as open as possible is one of the fundamentals of the project...

3) Well that offends me a bit but i would attribute this opinion of you to the fact that i do not necessarily share the language of the "military sub builder tribe" ... if you are a English speaking native military sub builder you will possibly find the German reference "tower" for a submarine superstructure where the English correct one would be "sail" and the Spanish one "vela" - please do not interpret that as "lack of knowledge" just as the fact that my sub building knowledge is patchwork of 3 languages

4) Yes, one could say that to certain extent - with all its advantages and disadvantages of which i am aware of ...

5) I would say i have studied sufficiently all pitfalls that ever happened in submarine history - maybe except some military and therefore not published - i would be glad to hear of from you...

6) possibly any MILITARY engineer - which is not exactly my brand - so i would like to keep it less military sub focused...

7) i see myself more as the manager of a "move submarine yachting forward project" than the "engineer of a specific vessel"...

8) i agree with you - it might be that this forum is a bit engineering overloaded for a concept discussion - i just try to keep most bases covered...

9) Makes me feel a little uncomfortable - sounds like school... teacher examine you

10) Military operator...due to the characteristics of THEIR boats...that have little - or nothing to do with MY boats...

11) sounds like "consider spin out of control" to a airbus A380 engineer - it may be a option for military to consider that - finally they operate close to such limits all the time - in civilian use you normally do not "consider" that kind of things as you stay sufficiently far away - what is reasonable security is most of all defined by the operation envelope ...

12) yes, military, - the civil submarine industry in fact has a perfect security record...

13) vent water ballast is a military concept - i am not very keen with safety by high pressure air as the safety system becomes a safety risk itself...i understand the good reasons why military use it - would like to work around it...if possible - what do you think?

14) I agree with that - and add the budget they can afford...

15) for a good reason on a military sub that runs what i would call "risky operation" with unstable dynamic diving, high speeds (speed kills) short reaction times, etc...on a civil sub of my brand things go much smoother, less "emergency" less close to the edge - this defines safety a bit different...the best way to handle emergency is avoid conditions to come to one...

16) i agree - If you go for drop ballast - 2 ways of release are fine -

17) i like the general idea of a hydrostatic device to trigger emergency measures - at the moment i am investigating in that direction...

18) ... i dont know - additional through hull rotating shafts to increase safety - the safety sistem is converting in safety risk (additional through hull) - kind of balance act...carsten of euronaut has a couple of them...i would like to work around that...

[MikeJohns]

Here is a good start for the submersible designers library:


Concepts in Submarine Design.
Burcher, R., and L. Rydill.
Cambridge University Press
January 28, 1994. ISBN: 9780521416818.

[harlemriverman]

Originally Posted by ancient kayaker

I read the previous postings. Again. There is no consensus that I can form, just a lot of conflicting opinions. I don't know the contributors so I don't know who is informed and who like myself, is looking at something new and wnating to learn more.

I accept your refutation of my remarks about bridge footings, I should have made my lack of knowledge clear and trust you are speaking from knowledge, but I would have thought the main challenge there would be undercutting by the current.

Failures due to vibration: is that relevant here? It is hard to imagine a slow-moving tube of concrete floating in the water having a vibration problem. A bridge deck or support is quite another matter.

You mentioned failures due to moisture penetration and also expansion stresses resulting from temperature changes, which sounds like you are concerned about repeated frost cycles. My concrete basement handles a temperature difference of 60 deg and a range of 80 deg on one side, and it didn't seem too bothered when it leaked for a couple of seasons and I'va had no further problems since slapping on a bit of hydraulic cement 25 years ago. Extreme temperature cycles are easy to prevent in a submersible craft not used in the winter, just add enough ballast to sink it when you let the air out of the tanks; pump 'em up in the spring. That assumes access to sufficiently deep water, but seems reasonable if you have a submarine

The thought behind my suggestion for using unreinforced concrete was this: the modulus of elasticity of concrete is 1/10 that of steel; placing a hollow ferro-concrete vessel under considerable pressure could therefore result in the steel imposing tensile forces on the concrete from within, with predictable results. Unless, that is, the steel was pre-stressed, but I haven't seen that mentioned yet. I don't have relevant data for fiber reinforcement.

I can't change my mind, it's not made up yet. I agree that Wellmer has not yet made his case; I think that we both are inviting him to do so.

a pressure vessel would undergoe compressive forces only when the loads upon the vessel are constant and static, and the shape of the vessel is such that tensile forces do not develop.

i cannot think of practical case where the shapes presented here would not develop substantial tensile forces derived from moments, torsion, friction, and differentials, thermal, dynamics, etc. plus i cannot think of conditions under which protusions do not create concentrated load conditions.

reinforcement need not necessarily be steel, per se, but that would be an economical approach. alternative stratgies might involve fibers of various kind but i don't have a great deal of success working with these applications and would not trust these under even shallow dive conditions of say 20 meters.

hunting was great this year. the deer must be feeding on corn, the venison is so good even my wife will eat it...which says a lot, she won't touch anything not wrapped in plastic.

[harlemriverman]

Originally Posted by rwatson

Are you not reading the previous postings at all ?

Both HRM and myself have identified a lot more than just compression forces at work here on the concrete structure.

Temperature changes alone will create severe expansion stresses - forces that destroy great basalt monoliths, let alone a couple of truckloads of aggregate with a hole in the middle.

The comparison to Bridge footings is totally unsuitable, despite Wellmers attempts at his website by quoting huge concrete structures as a basis for the viability of his project.

I have come across papers on the internet that discuss failures in even glass fibre re-inforced concrete structures due to vibration and moisture penetration.

As a skeptic, I at least can change my mind when the concept is proven, but it sounds like Wellmer and maybe others have quite a bit of time and money invested, and cannot possibly admit the possibility of failure. Certainly the silence on a lot of points about the project ( as you observed) dont build my confidence.

i'm with you rwatson, been thinking about this concrete sub notion while hunting...not much else to do most of the time. here's some of my revelations.

fiber is out or i'm not aware of materials whose mechanics overcome issues that would prove unmanageable in my humble opinion.

i'm going to try and come up with a math model, which i caveat with these can be terribly impractical. contemplating a hybrid steel shell bonded to a concrete core. i'll start with a finite model and give loads i can imagine, which i douible caveat with i'm not a nautical engineer. then i'll blow it up to the macro and work my way to the model. i'll post the results here for review by people in the know, such as yourself, but my gut is this takes us down the path of hybrid approach to reducing steel in a sub, if that's possible, but i'm anticipating more obsticles and questions as i spend a little time meandering down this road.

for giggles i'll try concrete only, but as i sat there freezing my butt off looking for bambi, there is so much about concrete that just screams for good old fashion, a60, epoxy coated steel that i'm clearly not getting it.

so here i go, down my math road, and i'll keep looking here for your astute comments and suggestions as i march along, in between beer and whiskey and my wife wondering why the hell i'm working on the computer so late at night. i just love a good challenge.

[ancient kayaker]

Reinforcement in a concrete structure is arranged so static and dynamic loads are always reacted by tension in the reinforcing material and compression in the concrete. Where prestressing is used the design is arranged so working loads increase the stress. If the design allowed a load to decrease the stress, eventually tension could result in the concrete, a situation which is avoided like the plague.

In a submarine made of prestressed reinforced concrete, the tension in the reinfocing material induces compression in the concrete. As the vessel submerges, additional compressive forces are applied which would apply to both the concrete and reinforcing material. Once the tensile stress in the reinforcing material passes zero it is under compression, applying localized tensile forces to the concrete in opposition to the externally-applied compression. Because the reinforcing material has a much higher modulus than the concrete a point will be reached where the concrete is under localised tension. This point is reached sooner in a non-prestressed reinforced concrete. I would want to be reassured that this point would not be reached while I was aboard.

With a sub made of unreinforced concrete tensile stresses in the concrete can only result from dynamic forces, like hitting something or moving fast, not from the static effect of depth.

I'm not saying it's a good idea, mind, just that I worried about unforeseen effects of using reinforcement. A fiber with a modulus close to that of the concrete would not have the same concern.

[wellmer]

Originally Posted by ancient kayaker

...worried about unforeseen effects of using reinforcement.

Yep, you have a point there...testing suggests that concrete structures WITH rebar can fail earlier than structures without rebar - when submerged at depth...10%

Cheers,
Wil

----------------

Title : Behavior of Steel Bar Reinforced Concrete Spheres under Hydrostatic Loading.

Descriptive Note : Technical note Jun 71-Oct 73,

Corporate Author : CIVIL ENGINEERING LAB (NAVY) PORT HUENEME CALIF

Personal Author(s) : Albertsen,N. D.

Report Date : APR 1975

Pagination or Media Count : 27

Abstract : Four reinforced and two unreinforced concrete spheres of 32.00-inch outside diameter (OD) and 2.71-inch wall thickness (t) were tested under hydrostatic loading to determine the effect of embedded steel reinforcement on structural behavior. Test results show that the reinforced spheres (0.44 or 1.10% steel by area) failed by implosion at values for the ratio of implosion pressure to concrete strength that were on the average 5% lower than for the unreinforced spheres of the same size. In addition, the reinforced spheres developed cracks in-the-plane-of-the-wall at the inner surface of the reinforcement cage prior to implosion. Implosion results for the unreinforced spheres are 10% lower than predicted by an empirical equation developed from previous tests of unreinforced 16-inch OD spheres. These results provide initial insight into the behavior of hydrostatically loaded steel bar reinforced concrete spheres and indicate that additional test data is required before definitive design guides can be developed.

Descriptors : *UNDERWATER STRUCTURES, *REINFORCED CONCRETE, CRACKS, SPHERES, STEEL, FAILURE(MECHANICS), REINFORCING MATERIALS, HYDROSTATIC PRESSURE.

Subject Categories : MARINE ENGINEERING

[ancient kayaker]

This is fun. Concrete is cheap so use it if you can. Talk is even cheaper, so we are all helping the economy here.

[harlemriverman]

Originally Posted by wellmer

Yep, you have a point there...testing suggests that concrete structures WITH rebar can fail earlier than structures without rebar - when submerged at depth...10%...Behavior of Steel Bar Reinforced Concrete Spheres under Hydrostatic Loading...

paranthetical comment but i'm starting to empathize with rwatson's concern with legitimacy.

as a former civil engineer corps officer, u.s. navy, i can tell you that you are referring to a study that has little to do with your postulate.

most of the banter here is in context with submerged conditions. the challenge facing a submarine would have at least four sets of conditions: 1) surface; 2) submerged; 3) dock; and 4) dry dock. there are probably more but i wouldn't know.

i'll be getting back with some facts shortly.

[CML UK Ltd]

We were asked to work on a conrete hulled boat. The owner wanted us to use pigs blood as a binder. Needless to say we let that one go.....

[wellmer]

Originally Posted by CML UK Ltd

We were asked to work on a conrete hulled boat. The owner wanted us to use pigs blood as a binder. Needless to say we let that one go.....

Are you ridiculizing concrete as a suitable material for marine pressure structures ?
Please update with the following...

...This program has been a decade-long demonstration of the effective use of concrete in the ocean; it has been shown that concrete is a durable, reliable material for pressure-resistant structures for long-term deep-ocean applications...

----------
A Decade of Ocean Testing of Pressure-Resistant Concrete Structures
Rail, R.
Naval Civil Engineering Laboratory, Port Hueneme, CA, USA;

This paper appears in: OCEANS
Publication Date: Aug 1983
Volume: 15, On page(s): 593- 597
Current Version Published: 2003-01-06
Abstract
By means of long-term deep-ocean exposure and laboratory testing, experimental data have been obtained on compressive strength behavior, permeability, and durability of pressure-resistant concrete structural models (concrete spheres 66-inch O.D. by 4-1/8-inch wall thickness) subjected to continuously sustained hydrostatic pressure loading. After 10-1/2 years of ocean exposure at water depths of 1,840 to 5,075 feet, the major findings include: (a) The implosion (failure) strength and stiffness of the concrete spheres and the uniaxial compressive strength of concrete specimens increased during the first 5-1/2 years exposure in the ocean and remained essentially constant during the next 5 years; (b) There has been no evidence of seawater permeating through the walls into the interior of ocean-exposed spheres externally coated with a waterproofing material; uncoated (bare concrete) spheres have a very low rate of water ingress, i.e., a permeability coefficient of about10^{-14}ft/ sec; and (c) Visual inspection and microstructure examination of retrieved specimens have not revealed any significant deterioration of the concrete matrix; no corrosion was visible on steel reinforcing bars which had as little as one inch clear cover. This program has been a decade-long demonstration of the effective use of concrete in the ocean; it has been shown that concrete is a durable, reliable material for pressure-resistant structures for long-term deep-ocean applications.
---------------------

See also what engineers that are aware of this conclusion do in concrete...





Image 1

Statoil's massive concrete based Heidrun platform. The legs of this platform reach over 100m down into the sea. Basicly this floating city is based on the fact that a concrete hull can withstand the ocean pressure stroms and waves all the way from surface to 100m depth during decades - without any alteration.


Image2

Inside the concrete leg of a drilling platform. (Troll Platform) Those engineers at the moment of the photo are tecnically "dived at 300 m protected from water pressure by a submarine concrete hull" of collosal dimension that stands vertically instead of horizontally - just flip that platformleg (in your mind) 90 degrees and add a propeller - you have a giant submarine of 24m diameter with 1m wall thickness and 300m length. This is not a new horizon tecnically speaking - it is just to see things from a slightly different angle. By the way my prototype submarine had a wall diameter ratio of almost exactly the double of troll - so it is good for water pressure at 600m including a similar security factor.


Image3
Grande Dixence, on the river Dixence in Switzerland, concrete dam. It was built between 1953 and 1961 to a height of 285 m (935 ft). Concrete at the foot of this dam holds a watercolumn of 285m - equivalent of 285m dive depth in a submarine.

Image 4
HIBERNIA CANADA, drilling platfrom 105.5m deep diving concrete submarine hull...

Image 5
Golf of Corinth Greece, the legs of this bridge go 70m down to the ocean floor. They where built at sea in floating status and do rest on ocean floor with very little force to enable the bridge to move in case of earthquakes - so this bridge is founded on 70m deep dived submarine concrete hulls.

Image 6
Seikan Tunnel - This train emerges from the depth of 240 m below the sea of japan where ist was protected during his passage by nothing else than a submarine concrete hull - horizontally in this case...

source:
concretesubmarine.com

----
So in conclusion i see no big problem in making a streamlined concrete tube and submerge it a few meters - in fact i already made and dived sucessful concrete submarine yachts in the ninties ...is there really still someone who doubts that concrete is a suitable building material for submarine pressure applications ? - if i do not answer to most of the questions that appearently bring up "unsolvable problems in using concrete for a submarine application" just let me kind of mude... with all those excellent examples surrounding us in daily life - i apologize for pulling out sometimes somewhat of that kind of "not very productive discussion"

Cheers,
Wil
concretesubmarine.com

[wellmer]

Now that raw hull building is almost finished i can share pictures and video.

Get a look at Ian's Yacht Sub at:

http://www.youtube.com/watch?v=zLv22CPYFSo



Cheers,

Wil

[mydauphin]

I think the hardest part of concrete hull submarine is the thru hulls, windows, ports, shafts,etc... You can make a perfect sphere take any pressure, but in order to get in sphere you need a hatch there you have a mix of materials. Whenever you mix materials there is failure point.

[Jimbo1490]

Seems like you could make all the 'through-hull' fittings, even the entry hatch(es) out of steel and bond them into the concrete hull very securely. These steel fittings should easily be able to carry any loads that would have been carried by the concrete that is 'missing' from the drilled/cut through holes.

Jimbo

[mydauphin]

It seems that concrete would be under tremedous pressures to separate from the steel embedded in it. It may take it but the cycling of diving and surfacing would cause microcrack that would cause it failure over time.

[Jimbo1490]

Steel is stronger than concrete. An integral flange could easily be built into any such ports to further spread/carry the loads from around the opening back to the concrete adjacent, so that there is no disturbance in the load path (load concentration).

Jimbo