Barge Stability

Discussion in 'Stability' started by Hussein Atwi, Apr 12, 2019.

  1. Hussein Atwi
    Joined: Apr 2019
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    Location: houston

    Hussein Atwi Junior Member

    Hi, I currently started my first internship after graduating, I work mainly on Heavy haul. I have been tasked to learn and attempt to create an excel sheet that does Hydrostatic stability calculation for barges. In essence, what they want me to create is If we have Object ABC and we know the size of the barge that will be used to Offload the pieces etc.. I want to be able to calculate all what is required on to ensure nothing tilts I guess. Sorry, I'm a newbie and would appreciate help or guidance on what I should look into and what to focus on. I will also add an example of the barge that we commonly work on.
     

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  2. vv3k4i
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    vv3k4i Junior Member

    We definitely shouldn't give you a strict answer how to do it. This should be your lesson. But I'm sure we can guide you.
    Excel gives you opportunity to implement your own code. This is visual basic if I remember correctly. So use it.
    All the software works in similar way. You get a volume, which you integrate to treat as a series of areas, and those areas you also integrate to treat as a series of smaller areas.
    In your case you should treat this task in 2D rather than 3D, which makes it fairly trivial.
    I think what you should concentrate on is how to describe a introspection.

    In simplest case you will have X,Y coordinates of 4 corners of crossection and by interpolation you search for remaining 2 points, which are the intersection of your shape with waterline. This way you will get all the 2D coordinates you need, and with use of them you can calculate area properties.
     
  3. Hussein Atwi
    Joined: Apr 2019
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    Hussein Atwi Junior Member

    Thank you for the prompt response, Of course I was not aiming to get the right answer. I am just trying to limit my searches to what I should be focusing on. I have little knowledge in excel but that should not be an issue with all the tools available online. My only issue is to know how to look for barge stability related I found several PDF's but was not sure If I was looking at the right thing.
     
  4. DCockey
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    DCockey Senior Member

    Do you have your textbooks from university? Which textbooks were used in your course(s) on stability and hydrostatics?
     
  5. Hussein Atwi
    Joined: Apr 2019
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    Location: houston

    Hussein Atwi Junior Member

    None was used, I'm a mechanical engineer recent grad but have not been in contact with anything similar. Do Small barge differ from Large barges? I have plenty of PDF's that I am currently reading, and I have also ordered this book on amazon
    "Ship Hydrostatics and Stability 2nd Edition by Adrian Biran."
     
  6. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I do not know the studies or degrees you have, nor do I think that is very important, but what is clear is that you need a lot of help. If you want to tell me what you have done and how you are going to approach the problem, maybe I can help you to go the right way. I will not do the road for you, the road you have to undertake, but I, and other people in this forum, can tell you if you are going well or wrongly. How have you thought about doing it? Let's leave aside, for the moment, Excel, first you need to know how to do it by hand before becoming a programmer.
     
  7. Hussein Atwi
    Joined: Apr 2019
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    Hussein Atwi Junior Member

    I mean I do agree it does not matter what the studies were, but my response was to DCockey when he mentioned textbooks used. So far I am still looking at what factors come into play when it comes to a vessel's stability. I found so far :
    1. I need to calculate the KG and LCG (Kg of the ship of course is always a variable and changes also during operations of loading and discharging)
    2. I will need to add the moment and position of C.O.G of the vessel and the cargo. which can be expressed as KG=Total vertical moment / total weights.
    3. Calculate the transverse metacenter (which is when the ship is at an incline) KMt=KB+BMt where KB is morrish formula for the height centre of buoyancy above the kneel). One way was approximating KB by using this formula which is KB=1/3(5T/2-V/A) where T is the draft V is volume of displacement and A is waterplane area. even though i found that can also be determined using hydrostatic properties table but I couldn't find a decent one yet.
    4. BMt is the vertical distance from B to Mt I=(LxB^3)/12 where I is moment of inertia, B is breadth of waterplane( if it's a rectangular shape) if it's not it's I=Lx B^3 x k
    Now there is still more that I found but I'm hoping on that I am on the right path.
    There is still the need to take into consideration the effect of Rolling, pitching and Ballasting.
     
  8. Heimfried
    Joined: Apr 2015
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    Heimfried Senior Member

    Hi Hussein,
    I did an excel folder with hydrostatic calculations for recreational boats a few years ago. There is no real difference between large and small floating bodies (vessels, boats, barges, ...).
    My solution was to "cut" the hull into vertically oriented "sticks", up to 93,750 (250 * 375). (I point to "Biran Hydrostatics", but I've got the 1st Edition.)
    The system of coordinates I used is shown in Biran, 1.4.1 (p. 9), The cuts are at 375 Stations and 250 Buttocks (Biran, 1.4.2). For each stick (same cross section area all of them) it is easy to calculate its depth of immersion and the coordinates of its center of buoyancy. Sum this up as moments (buoyancy force and lever) and you will get the coordinates of the COB (center of buoyancy) of the hull.

    I later wrote this calculations in php and put it on a website: Berechnung der Schwimmlage von Booten http://www.bootsphysik.de/

    Button "English" top right on the site.
     
    Last edited: Apr 15, 2019
  9. Heimfried
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    Heimfried Senior Member

  10. vv3k4i
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    vv3k4i Junior Member

    I can agree, that if you had no contact with hydro statics or stability before this could be more challenging for you to accomplish this task. Why don't you use some freeware software like delft ship? This would allow you to understand stability, you would also avoid mistakes on the way.
     
  11. messabout
    Joined: Jan 2006
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    messabout Senior Member

    In you original post you said that....as far as I understood your statements.........that shifting weights should not alter the angle of "tilt" . That condition would not adhere to the laws of physics. If you balance a body about a mid point...we can call it center of buoyancy , (CB)... then any shift of weight will neccesarily influence the immersion of the buoyant body and therefore the angle of tilt (heel) or pitch as the case may be.

    Not to be nitpicker here but can you state the requirements more specifically?
     
  12. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Indeed...

    When a weight onboard that has moved causes a permanent change in the angle of floating it is call List ...Heel is a temporary state, like wind.
    There is no 'tilt' terminology as far as i know!
     
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  13. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    My guess is he needs a spreadsheet to plan out positioning of cargo on a barge so it's balanced and minimizes list and pitch and retains enough stability.

    I wonder what would be most practical for them. Maybe a website where you can edit and see the positioning of cargo, and send that layout with via a link with email or text to the loader.
     
  14. Ad Hoc
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    Ad Hoc Naval Architect

    By pitch, you mean Trim.

    Trim is a static condition, like List.
    Pitch refers to dynamic condition, i.e. motions.
     
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  15. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    Thanks Ad Hoc!

    Cunningham's Law: "The best way to get the right answer on the internet is not to ask a question; it's to post the wrong answer." :)

    It's apparently why wikipedia works.
     
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