Structural glass on hull sides - ISO Harmonised rules

Discussion in 'Class Societies' started by ToMeK, Mar 12, 2021.

  1. ToMeK
    Joined: Nov 2006
    Posts: 41
    Likes: 3, Points: 8, Legacy Rep: 10
    Location: Zagreb, Croatia, Europe

    ToMeK Young naval architect

    Hello everyone!

    Please help me with an advice and guidance where to look for the rules for scantling of large hull side windows. Project is small planing boat 45ft GRP.

    According to ISO 12216 in Area I (on the hull side below hs) smaller dimension of appliance must not be larger then 300m (b<300mm).

    My conclusion is that this glass must be taken as structural, but I am having difficulty finding adequate rules glass calculation should be made according to. Does anyone have any experience or an advice? If possible it would be good to keep boat under ISO class.

    Similar example is GALEON 700 SKYDECK 2021 with obviously large glass areas on sides close to WL.

    Many thanks,

    Best,

    Tom

    Galeon 700 skydeck 2021 - p5.jpg Galeon 700 skydeck 2021 - p4.jpg
     
  2. TANSL
    Joined: Sep 2011
    Posts: 7,369
    Likes: 699, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Use the theory of thin sheets, with four recessed sides, and with a thickness such that the maximum deflection of the plate is not greater than its thickness.
    The maximum dimension of each window should not be greater than 1 m, or two times the value of frame spacing (the less value)
     
  3. ToMeK
    Joined: Nov 2006
    Posts: 41
    Likes: 3, Points: 8, Legacy Rep: 10
    Location: Zagreb, Croatia, Europe

    ToMeK Young naval architect


    Thank you. It is not a problem to calculate it that ways, but the questions is if the surveyor will accept it since the smaller dimension is longer then 300mm (not acc to ISO 12216).
    I found ISO 1336-2 which is for large yachts considering glazing as structural part but taking into account only local loads on glazing plates. Do you have any experience with that?
    In the end, FEM calculation can be made for this (as you said under 1m span and deflection less then 1/2 of thickness it can be considered as linear static)

    Regards,

    Tom
     
  4. TANSL
    Joined: Sep 2011
    Posts: 7,369
    Likes: 699, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    I have done several projects of passenger ships with windows in the bottom. I have followed the rules of the Spanish Administration which, in terms of the calculation method, are reduced to what I have told you. These standards also speak of a maximum width of 0.5 m but I have presented openings of 1 m, justified by the calculation, with an extra reinforcement in the hull (double thickness of the laminate) in the area where the openings are placed, and metal frames . With all this, they have accepted the projects without any comment to the contrary.
    All the rules, even those of the Classification Societies, may no longer be met, if you justify your calculations properly.
     
    jehardiman likes this.
  5. jehardiman
    Joined: Aug 2004
    Posts: 3,762
    Likes: 1,152, Points: 113, Legacy Rep: 2040
    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    I support TANSL on this, as most societies have an "or engineered equivalent" clause. The rules are made to make plan inspection easy, not be a technical limit. However, the one rule you can't get around is that the glass cannot be proud of the line of the hull however it is measured. So you need to be diligent in way of curved hull sections.
     
    fallguy likes this.
  6. TANSL
    Joined: Sep 2011
    Posts: 7,369
    Likes: 699, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    I forgot to add that, in the hull, glasses, and the area where they are or implanted, must be perfectly flat. Although I suppose this is obvious.
     
  7. fallguy
    Joined: Dec 2016
    Posts: 7,598
    Likes: 1,674, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    I believe that no element, including metal, can be proud of the hull line.

    @TANSL How does one make all elements flat? Or is the metal frame proud of the glass, but not proud of the hull? Hard to tell by the picture above, but it appears to be double recesses. So the entire area is recessed? and then the windows are recessed? behind the metal framing.

    I am only curious and not trying to answer the original question. I imagine those windows are a bugger to keep salts spots off!

    When I built my small boat, my ports are behind the hull line, but the flange is proud of the hull and so I was rather stressed about it for a bit. That is nothing compared to these windows.

    If they recess it all, then the fiberglass can be thickened. Perhaps this is all a no brainer for you fellas. If so, carry on and with my apologies.
     
  8. Scarf
    Joined: Mar 2021
    Posts: 10
    Likes: 0, Points: 1
    Location: France

    Scarf Junior Member

    The ISO 11336 standard you refer to allows a maximum clear opening size of 0.85m^2 and it is intended for large yachts > 24m, design loads on the side shell may be higher than ISO 12216 though. Large glazed openings are also sometimes accepted if they are constructed of laminated glass with a PVB interlayer between the panes which improves the impact resistance and also provides residual strength if one of the panes is broken. Glass thickness should be determined by the formulae in the standard, FEM is not really necessary for a simply supported monolithic pane but if you do decide to use FEM then a safety factor of 4 should be applied on the characteristic failure stress of the glass.
     
  9. CocoonCruisers
    Joined: Dec 2015
    Posts: 95
    Likes: 39, Points: 18, Legacy Rep: 10
    Location: Marseille & BuenosAires

    CocoonCruisers Junior Member

    Hi, has the op or someone else solved this in ISO 12216-2020 ?
    We are running into similar problems for an 18m motorsailor design and remain somewhat confused seeing that:

    - ISO 12215-5 does not include structural glassing and refers to ISO 12216 for any window

    - The scope of ISO 12216-2020 excludes "Openings and non-openings fitted below area I (see 3.5.2)

    - Paragraph 3.5.2 of ISO 12216-2020 sets a lower limit "hs" of said area I
    --- at 0.5m for Category A
    --- at 0.4m for Category B

    - ISO 11336 only applies to 'Large Yachts" , meaning more than 24m

    - The 2021 Galeon 700 Skydeck the op posted is category B, and its masters stateroom windows appear lower than 0.4m to me,
    but perhaps they just got the styling to suggest that, with the black framing etc.
    Sadly i can't find a pic where i could measure reliably.
    What do you think ?

    Am i missing an element of the regulatory framework that would allow to go lower than 50cm within EU RCD Cat A ?
     
    Last edited: Aug 26, 2022
  10. TANSL
    Joined: Sep 2011
    Posts: 7,369
    Likes: 699, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Glass windows can be put up to below the waterline. If the ISO does not study these cases to which you refer, there will be no choice but to use the regulations of some Classification Society or, for example, Timoshenko's thin plates theory and carry out a direct calculation.
     
    CocoonCruisers likes this.
  11. ToMeK
    Joined: Nov 2006
    Posts: 41
    Likes: 3, Points: 8, Legacy Rep: 10
    Location: Zagreb, Croatia, Europe

    ToMeK Young naval architect


    Hi CC,

    We had a problem but we managed to solve it with help of certifying body (IMCI in our case). We were required to respect min height of 0.2 above WL and use laminated toughned glass. When I get to my computer I will search for a spreadsheet we used. It was combined calculation aproach using ISO 12216 and ISO 11336. The glass ended up crazy thick and heavy, but it was client requirement so we had to respect it.
     
    CocoonCruisers likes this.
  12. TANSL
    Joined: Sep 2011
    Posts: 7,369
    Likes: 699, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Hi Tomislav, could you tell me where ISO 12215-6 deals with how to calculate windows, additional reinforcement of that area, frames and types-thickness of their glass?
    I don't have nor am I familiar with ISO 11336. Does it solve this problem, is it worth buying?
    Many thanks.
     
  13. Alan Cattelliot
    Joined: Jul 2021
    Posts: 505
    Likes: 209, Points: 43
    Location: La Rochelle (Fr)

    Alan Cattelliot Senior Member

    Dear All,

    I follow this discussion with a great interest, since I was wondering, like ToMek, how small crafts (under 24m) like the GALEON 700 SKYDECK, seen in Dusseldorf, were able to have such kind of large windows near to the waterline. I find very instructive and pertinent the answers given by TanSL, ToMek and CocoonCruiser. Guided by their remarks, I found this document, that will certainly be of some help, if swaps between required standards are accepted, in some cases.

    upload_2022-8-29_20-55-24.png

    Thank you.
     

    Attached Files:

    Last edited: Aug 30, 2022
  14. Alan Cattelliot
    Joined: Jul 2021
    Posts: 505
    Likes: 209, Points: 43
    Location: La Rochelle (Fr)

    Alan Cattelliot Senior Member

    !!!ESTIMATIONS - Don't know the web structure in way of windows - Possible black masking tapes - drawn waterline probably not in mldc !!!

    Assuming Lh = 21,95m, measurement are in pixels, taken from the image given in https://www.yates-mallorca.com/model-yacht/galeon-700-sky#uael-gallery-6
    conversion is made under the assumption that Lh = 21.95 = 968pixels

    panel center (of the elongated window) above waterline : 1.30m

    clear light dimensions (of the elongated window) :630mmx2300mm

    vertical distance from the bottom (of the elongated window) to drawn waterline :0.90m

    newplot(76).png
     
    CocoonCruisers likes this.

  15. CocoonCruisers
    Joined: Dec 2015
    Posts: 95
    Likes: 39, Points: 18, Legacy Rep: 10
    Location: Marseille & BuenosAires

    CocoonCruisers Junior Member

    Thanks to all, things become much clearer :))

    The occurences i spotted in ISO 12215-6
    (which references ISO 12216 for the thicknesses and materials):

    6.5 Window mullions

    A mullion is a stiffener supporting the window (i.e. the vertical frame of the window). Large openings, with or without windows, introduce demands on the mullion structure. The mullions shall be analysed under the two separately occurring load cases outlined below. NOTE It is assumed that the loads are transitory and will not occur simultaneously.

    ⎯ Load case 1: simply supported beams carrying a uniformly distributed load equivalent to the deckhouse side or front load, as defined in ISO 12215-5, according to position. The loaded width is to correspond to the mullion spacing where windows are fitted. The allowable stresses should be those specified in ISO 12215-5.

    ⎯ Load case 2: simply supported compression strut, carrying a load equal to the total pressure load on the deck structure, as defined in ISO 12215-5, supported by the mullions divided by the number of mullions that support this load. The compressive load at failure should be calculated using a Rankine-Gordon or Perry-Robinson style formula, which allows for interaction between columns and strut behaviour. The compressive load shall be at least twice the applied load as calculated above.

    With regard to the treatment of windows:
    a) non-bonded windows are considered non-effective;
    b) for bonded windows, the strength of the panels and/or mullion shall be analysed together.
    As glazing material used in windows, e.g. PMMA (acrylic) and glass, are more brittle than normal engineering materials, the safety factor shall be greater than that given in ISO 12215-5 and shall be taken from ISO 12216.


    11.5 Other structural components not considered in other parts

    Where calculations are not possible, the general requirements of this part of ISO 12215 shall be employed. In particular, the calculable scantlings from other parts of ISO 12215 for the adjacent structure shall provide a reference baseline for assigning scantlings to the following components:
    a) skegs (see ISO 12215-9);
    b) propeller struts;
    c) davits;
    d) windows (see ISO 12216);
    e) ventilation devices (air pipes, vent pipes);
    f) radar masts.
     
    Last edited: Aug 30, 2022
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.