Concrete Dock Float

I imagined this would be an easy topic to find extensive resources on, but it turns out not to be the case.
I need a concrete float to support a sewage treatment system beside a fixed facility.
The load is a large heavy set of poly tanks, specs as given. Might be easier to buy one, but maybe not.

 

1870 dry wt, plus 300 gallons raw sewage at 8.34, plus any rainwater or waves

1870
2502
Rain/snow/ human ? 400
weight of vessel

Total mass 4772 (okay, pounds) plus vessel

The obvious question is why concrete for the barge. Seems like metal pontoons or a metal barge would work. It is pretty heavy and gonna need a large footprint.

 

Concrete I can work with. I have heaps of navy jack, a flatbed of powder, a lift of plywood. Weight of the final product is meaningless. Steel requires boatyard workers. And this won't be maintainable. It goes in the water and never comes out until the facility it supports ends it's run.

 

It's no wonder you can't find specific "extensive resources". The NA part is the same as for a barge, make sure it floats level at rest, so you need to look at the plant operating conditions (worst case scenario beeing only one full tank with the rest empty, the dock needs to remain within specified operating angles).
The structural part is a waterproof concrete box, it needs to support the load/sqin while remaining in the tension and compression limits of the material.
Both are bread and butter tasks in their fields. There are tables for reinforcement type and spacing, concrete type and thickness (for example our norm recommends a minimum of 10 inches total wall thickness in the presence of liquid water). An engineer dealing with basements is usually up to it, on difficult ground their worries are to add enough weight so the structure doesn't float away, they know how to do buoyancy and weight distribution calculations. Ask the guy who does your foundations, he should be able to provide the engineering.

If you want to do your clients a favor ask the structural engineer to specify composite rebar, that way even if cracks develop they won't be a problem to repair.

I would be more worried about the building it on site, this things are heavy and you either have sufficient crane capacity or improvise a dry dock.

 

A side note, my wife and I spent $11,500 on bulkhead repairs and the idiots use metal rebar instead of composite to save a few bucks. Hairline cracks develop every 2 feet or so. They never run out of work. <sigh>

 

Thanks @Rumars. Ideally I can buy one and have it trucked up as far as Campbell River, then barged to Echo Bay.

 

Did you find one?

 

Not yet.

 

Hi DogCavalry, would a supplier to floating housing bases be of any help; some I've seen are sprawling multi story houses weighing many tons. Maybe source a second hand one, bag it, pump out the water, grout it to re-seal it, and deck it.

Also I was just reading about folks in 1936 Denmark making large floating concrete caissons upside down, floating them out, and capsizing them right way up at sea, still floating, before placement for bridge building. Put a deck on and you have your floating dock. Probably not exactly helpful for you, but possibly doable with your materials, skills and experience. The web site is - Home - Wonders of World Engineering https://www.wondersofworldengineering.com/index.html Part 16, at the bottom, Great Danish Bridges (part 1)

In the same type of 1936 magazine series is Home - Shipping Wonders of the World https://www.shippingwondersoftheworld.com/index.html ; which is un-related, but interesting, and a bit of a laugh these days considering it's between two world wars back then, when a ship with a radio transmitter was the latest in communication. A good read.
Good luck anyway, sounds like a big job.

 

So I designed and built a basic float. It carries about 4 tons, and its structure can carry point loads, and asymmetrical loads.

I have also reached out to some next level folks for direction in correctly building the next step up in size.

 

Is ot chambers or are the cross pieces just ties?

 

Seperate chambers. Good observation. The individual planks alternate running full length lateral or longitudinal with spacers running the other way in each level. That makes longitudinal and lateral full depth beams. 26" deep long, 23" deep lat. Or 66cm/58cm

 

So, what is the intent for this float?

 

It supports the water side part of a septic plant for a 100 seat restaurant on a repurposed concrete floating bridge segment, located in Echo Bay on Gildford Island.

 

Here we go. The CofG will be too high for stability once those tanks are full of grey and black water, do the dock will be mechanically attached to the sideof the main float.