Barge/pontoon Stability

[Mohanlal0488]

Hi Guys

There is no forum specifically for maritime engineering hence the post here.

I have been dealing with the design of pontoons for a number of years now, the pontoons are used for industrial and mining operations, and I have been adhering to our local rules and regulations.

Over the years I have developed a number programs to assess the stability of pontoons, my final method that I have developed uses a similar approach as finite element packages.

The pontoon floats are about 1 meter high and are generally designed to have a submergence of 60%. When performing stability analysis there is always a point in time whereby one side of the deck will be submerged in the water. This is taken into account in my finite element formulations and it ultimately has an effect on the righting arm. When considering the water on the deck, the righting arm becomes negative at a smaller heel angle, while without the water on the deck this occurs at a larger heel angle (See the attached images). Note that the results from the program have been checked by means of FEA software so they are correct.

So my question is when performing stability analysis using the traditional methods is the effect of water on the deck taken into account or is this neglected?

 

[3DDave]

Were it my problem, I'd sign up on gCaptain.com and ask the forum members there. Significantly more on-topic experience.

 

[LittleInch]

There are forums under marine / ocean engineers, but they are a bit of a backwater with few posts, but that's where you might find some traction. Also try a search on those forums. If you go into them and then click the search button on the top LEFT, this limits the search to that forum.

The question for me is what are the "traditional methods"? Are they in a code or regulation?

Do they assume that there is no submergence of the deck?

Or that a 40 degree heel angle is too far?

A diagram might help, but in terms of the post, I'm a little unclear what you're asking or why, given you seem to have a lot of experience in what looks like a fairly niche piece of engineering.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Mohanlal0488]

Thanks guys

Thanks for the inputs, I will look into your comments, I was unaware that there is maritime group here.

@LittleInch,The reason for my question is due to the lack of input from maritime engineers in my position, thus even though I have knowledge in the field, I am not fully aware of the deeper intricacies.

 

[MintJulep]

Are you considering that water flows?

 

[Mohanlal0488]

@Mintjulep Not sure what you mean by "flows"? acn you please elaborate?

What is considered, is the depth of water that exists on the deck at a particular heel.

 

[SwinnyGG]

Water flows- so the question is, at 40+ degrees of heel, how much water is actually retained on the deck of this vessel?

40 degrees is a LOT of heel. I have a hard time imagining your vessel would retain water at a heel angle that high- unless at that heel angle a portion of the deck is substantially submerged.

 

[MintJulep]

Are we discussing something like this?

Seems to me like the heel angle needs to be pretty rediculous before you would get a negative righting moment.

 

[SandCounter]

Not sure how your program works, but unless the water on deck is separated from the water the vessel is floating in and trapped as to add to the dead weight, it is contributing to the buoyancy of the vessel.

Are your plots perhaps mislabeled?

 

[Mohanlal0488]

Hi Guy

@Mintjulep yes something similar to that.

Thank you everyone for your comments and assistance. I actually managed to get in contact with a Naval Architect who assisted me with information and some stability analysis results for a test cases so that I can calibrate.

 

[chicopee]

In the past I have dealt with mobile and crawler cranes mounted on barges. Obviously appropriate load charts had to be developed to meet OSHA requirements and one particular OSHA requirement was the freeboard on all sides when the barge was listing or tilting. On occasion barge manufacturers could help when we were in a pinch for time. My suggestion is to contact the pontoon manufacturers for help. Also check the relevant technical manuals if they are available from the manufacturers.