Scantling / section modulus calculation

Discussion in 'Boat Design' started by EddieGreen, May 14, 2022.

  1. EddieGreen
    Joined: Feb 2021
    Posts: 18
    Likes: 2, Points: 3
    Location: Nice

    EddieGreen Junior Member

    Hi folks,
    I need to calculate the min. SM of this specific "bulb" bar (see attached drawing)
    attached to 300mm x 6m plating
    Thru tedious calculations i get a SM of c.a. 5.48 cm3 ( I : 24.37 cm4, v : est. 4.44cm)
    once attached to this 6mm thick plate. The SM of the bulb bar alone is 1.68cm3 .

    Would anyone with access to the right software check this 5.48 cm3 figure and give me a more accurate figure ? (used an HP profile square as a first estimate)

    I also need to make sure i am using the right figures for the design stress (direct and shear : sd and td) as per the latest update of the ISO12215-5,2019 or 2020 version ? This should be in Annex B page 58 or page 60 (i only copied page 59 unfortunately !) . I need the right data for several aluminum alloys incl. 6060,6082T6, 6005, etc I do have much data from supplier refs and older versions of this rule, but just want to make sure i am using the right ones as per this new/updated ISO norm.

    Many thanks for your kind help !
     

    Attached Files:

  2. TANSL
    Joined: Sep 2011
    Posts: 6,947
    Likes: 543, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

  3. EddieGreen
    Joined: Feb 2021
    Posts: 18
    Likes: 2, Points: 3
    Location: Nice

    EddieGreen Junior Member

    Thanks a lot for your timely response even on weekends !
    There is a radius 2 mm fillet on the upper left part too but the SM must be close enough. (my initial calculation was without any fillets)

    Is the above picture a direct output from your SCT software ?
    I still need to make sure i have the right data for the design stress of the a.m. alloys
    Thanks again
     
  4. TANSL
    Joined: Sep 2011
    Posts: 6,947
    Likes: 543, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    This values come from my software but you can do the same, very quickly, with AutoCAD
     
    EddieGreen likes this.
  5. Ad Hoc
    Joined: Oct 2008
    Posts: 7,276
    Likes: 1,165, Points: 113, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    That depends whether you use the commonly accept 50t for effective breadth of plate, i.e the plate, for the section modulus calculations is 4 (t) x 50 = 200.
    Or, as per ISO they use 60t = 240mm.

    Therefore
    Z = 5.43 cm^3
    I = 2.371mm^4

    Is is straight forward to write a simple excel spreadsheet to do this calculation too.

    ISO provides its own values, such as:
    upload_2022-5-15_17-43-12.png
     

  6. TANSL
    Joined: Sep 2011
    Posts: 6,947
    Likes: 543, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.