# Stiffener formula

Discussion in 'Class Societies' started by DUCRUY Jacques, Oct 18, 2011.

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### DUCRUY JacquesJunior Member

Hello,

You know the classic formula :

SM = (C b l² P) / admissible stress

In ABS and ISO rules, C is always 83.33 (end fully fixed). But it seems to me that Lloyds take C = 100 (end partially fixed) and DNV take 100 for transverse frame and 83.33 for longitudinal frame.

So, in practical, in what case do you use C = 83.33 or c = 100 ?

Thank you in advance.

Best Regards

Jacques

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### MikeJohnsSenior Member

Jaques
It depends entirely on the level of end fixity.
If you fully bracket a terminating end to another rigid member in the same plane then you consider it fixed. So it depends also on the construction method and material as to how effective end fixity is in shifting the point of contraflexure.

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### DUCRUY JacquesJunior Member

Thank you, Mike.

I assume that, for a sailboat, I can take C = 83.33 for stringers (continuous beam), but for transverse frame, il I had no true bracket between tranverse frame et deck beam, C = 100 is more correct.

Have a nice week-end

Jacques

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### MikeJohnsSenior Member

Yes any continuous framing is considered fully fixed at each point of support without bracketing.

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### DUCRUY JacquesJunior Member

Thank you very much.

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