Stiffener formula

[DUCRUY Jacques]

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

[MikeJohns]

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.

[DUCRUY Jacques]

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

[MikeJohns]

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

[DUCRUY Jacques]

Thank you very much.