ISO 1225-5-2019 stiffener calculation

Discussion in 'Class Societies' started by Robert03, Nov 18, 2023.

  1. Robert03
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    Robert03 New Member

    Hello good people,

    My student assignment is to make laminate calculation for 10m fishing boat.
    I read almost all threads on forum regarding ISO 1225 and I am aware that it is hard to understand complete document without any help.

    I need help regarding Table H7 - top hat stiffener calculation. I`ve tried to make table in excel and to replicate it with numbers and formulae, so I can get it all right, but few cells are giving me a headache.

    Everything is lining good, except I can`t get same values for Web above NA Depth, Web bellow NA Depth, Z neutral Axis zNA and H lower web above plating.

    Is there anyone here that managed to get same values as from example in ISO? Which formulae/input did you use to get values that give me headache?

    Also, I am little bit confused with ISO description of end type connections, as fixed end is described as continuous stringer. I have stringers, but they are mostly starting on bulkhead and finishing on bulkhead (it isn`t snniped), as I can understand that should also be stringer with fixed end, am I right?

    Hope that someone has resolved this, thank you all in advance!
     
    Last edited: Nov 19, 2023
  2. TANSL
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    TANSL Senior Member

  3. Robert03
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    Robert03 New Member

    Yes, ofcourse.
    I am available through furlicks@protonmail.com.

    Thanks!
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    Welcome to the forum Robert03.

    I don't have table H7 in my ISO, so can you post a drawing/image of what you're referring to please, just for 100% clarity.
     
  5. Robert03
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    Robert03 New Member

    Thank you!

    Here is the Table H.7 picture:
    upload_2023-11-19_12-23-37.png
     
  6. Ad Hoc
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    Ad Hoc Naval Architect

    Many thanks Robert,
    But without the diagram and dimensions of the 'worked example' that is referenced, it is not so easy to comment.
     
  7. Robert03
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    Robert03 New Member

    My apologies, sending more info:
    upload_2023-11-19_12-41-23.png
    upload_2023-11-19_12-41-45.png
    upload_2023-11-19_12-42-4.png
    This is all that is available in order to "get into" stiffener calculation and beside that, as I started this topic, I still can`t get same values for Web above NA Depth, Web bellow NA Depth, Z neutral Axis zNA and H lower web above plating.

    Thank you!
     
  8. Ad Hoc
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    Ad Hoc Naval Architect

    Before i delve deeper, you should first have a look at THIS post, showing the basic calculation for second moment of inertia of top-hat stiffeners.
    Try this, see how you get on...
     
  9. rxcomposite
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    rxcomposite Senior Member

    I have the 2019 spreadsheet version Table H7 and the old H4 version. Post the Excel spreadsheet you made as it is easier to troubleshoot.

    Seems to be more confusing than ever like putting the cart before the horse. Those distances you showed are derived values, not an input. There are two distances that are measured.
    1. The distance to the center of the laminate (from base) based on stacking sequence. This is used to calculate the EI of the laminate and the N.A..
    2. The distance to the outermost fiber of the laminate centered on the Neutral Axis (N.A.). This is used to calculate the stress of the laminate as max stress occurs on the outermost part of the laminate (layer). Negative if in compression. positive when in tension.

    As for the "FIXED END" of the stiffeners connected to or starting on bulkhead, that is a Primary Connection and uses a 1/12 constant (see Mb formula) on the bending moment equation. If the stringer is supported by the primaries, that is Secondary and the constant is 1/24 and uses a lesser Safety Factor.
     
  10. Ad Hoc
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    Ad Hoc Naval Architect

    The image of the data you posted, is blurred when i zoom in to lift off the dimension and check the data.
    So, not so easy to advise, without seeing their data to double check.
     
  11. TANSL
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    TANSL Senior Member

    Here you have Table H.7. Now it will be very easy for you to properly advise @Robert03 .
     

    Attached Files:

    Last edited: Nov 20, 2023
  12. Ad Hoc
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    Ad Hoc Naval Architect

    Ok, in the absence of table H6 not being posted, as noted above it is blurred when zoomed in, we can state the following:

    In Table H7, that column/row you highlighted, here:
    upload_2023-11-21_9-8-12.png

    Thus what is a web, in this case it is this part of the structure:
    upload_2023-11-21_9-10-49.png

    The web that is below that NA axis that is drawn, is that which is shown highlighted in red.

    In column 11 of Table H7, is says Depth, h, mm.

    So the depth of that small part of the web, noted in red, is simply (23.2-3.36) = 19.84mm, which is not 24.1mm.
    Therefore, there must be 'something' in Table H6 (which is blurred and cannot read it) that either explains why this value is 24.1mm, or, why it is incorrect.
     
  13. Ad Hoc
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    Ad Hoc Naval Architect

    Thank you, but that is not the table requested.
    If you consider this to be easy, im curious why you have not answered the question then?
    You were the first to answer this thread, but very oddly provided no substantive answer, you just wished to go to a private conversation?
     
  14. Boat Design Net Moderator
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    Boat Design Net Moderator Moderator

    To anyone replying to this thread, please be careful that anything posted or attached does not violate ISO's copyright. Many thanks.
     

  15. Ad Hoc
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    Ad Hoc Naval Architect

    I do not believe any has been.
    As per their own statement on such:

    "..10.2 Fair practice
    CCMC determines, at its own discretion, that a request to reproduce a small extract of a Publication can be considered as fair practice. In such cases, it may give permission for the reproduction, subject to an appropriate acknowledgement. ...Typically, fair practice may include quotations for review, comment and analysis in documents and publications made for non-commercial educational or informational purposes. Small extracts consist of limited text, data, figures, tables, pictures or drawings, which are not fundamental or essential parts of the Publication.."
     
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