Marine winch foundation

[greycloud]

Hi there everyone

I'm working on calculating the stresses in a winch foundation installed on the main deck of a barge. the pull on the winch causes both axial and bending stresses in the foundation under the winch so here is the problem. I looked hard for an equation that deals with critical buckling strength due to bending and one for getting the applied bending moment on the foundation cross section but couldnt find any. the foundation is composed of a plate with transverse and longitudinal stiffeners attached to it beneath.

I hope some one can reference me to such equation or to a book talking about this matter.I attached a drawing of this problem

Thanks and help appreciated.

 

[BigInch]

How big is the ship and the winch? What's it weigh? And what are the values of the loads you show, or rated cable force? Size and higher loads may have some bearing on how exotic you need to get with the calculations. Is it motorized? What is the horsepower of the motor? What is the short circuit load?

Convert the two loads into one resultant load (including dynamic load factors). BTW there is a torque load when the winch is revolving.

Many times this problem can be broken down more or less to just P/A + Mc/I and shear loads.

Blodgett, "Design of Welded Structures" could give you some ideas on how to handle a base plate design.

Learn from the mistakes of others. You don't have time to make them all yourself.

 

[greycloud]

biginch:thanks for your reply. the winch is to carry a load of 40 tons and can be more after taking dynamic factors into consideration. I got equations for uni axial compression critical load but I can't find any equations talking about a moment such as that I'm encountering in this case.it is applied in middle of the plate and thus I believe this moment results both in torsional and bending stresses. I will check the book you described and hope i find what i need there.

 

[BigInch]

Reasonably heavy load. Do you have a structural engineer that can advise you.

Learn from the mistakes of others. You don't have time to make them all yourself.

 

[greycloud]

no unfortunately

 

[dhengr]

Greycloud:
It would be a good idea if you did hire a Structural Engineer to help you with this problem. Because, your sketch and the way you have described the problem leaves so much important design info. undefined, and so much to the imagination of people here, who can’t see what you have and are looking at. This makes it impossible to begin to respond to your question. So far, it appears that you are in way over your head, and a couple simple equations aren’t going to solve your problem or help you out, in fact, they may just get you in trouble. Looking for a couple equations or formulas is just not the way to approach this design problem. You need much better sketches of the winch and of the deck structure, including dimensions, member sizes, material properties, loads and load combinations. These should include plans, section views, elevations, etc., enough to fully define the problem. And, should also include the manuf’er’s. data sheets on the winch. This is not a trivial problem for many reasons, and you should probably not be doing it without someone with experience supervising the design effort.

Also, E-Tips generally frowns on double posting the same question in several different forums. Although, in the two forums you have posted this OP, you certainly will get different answers from different groups.

 

[MikeHalloran]

Barge structures don't look like what you have scribbled.
That's not a drawing. It's not even a sketch.

You need to go to the actual barge and measure every dimension of the unit cells under and near the proposed mounting location. You need to measure the thickness of every plate, with a micrometer, because the plates that comprise the typical egg-crate structure are thin, none of them stand alone, and the exact dimensions are important.

While you are there, measure and photograph the structure around the bollards and any existing deck winches, to give you some ideas about how things are done.

Then, rent a structural engineer. (S)he will need decent sketches showing the dimensions you measured, or you will have pay him or her to make the measurements. ... or find the barge's actual construction drawings.






Mike Halloran
Pembroke Pines, FL, USA