Re: [PSUBS-MAILIST] Hull Design

["Sean T. Stevenson" <cast55@telus.net>]

On Tuesday 28 December 2010 17:38:34 you wrote:
> Hi everybody,
> 
> I have a question regarding hull design. In that, on what basis we should
> select center to center spacing of stiffeners. Ls (refer section 19.1 ABS
> rules)
> 
> Thanks,
> Gandhi

Ls is distance between centroids, and Lb is unsupported distance between 
stiffeners (this could be larger than the centroid-to-centroid distance if 
using asymmetric stiffeners).  L, for the purposes of the calculations given 
in 6.19.5.1 is the larger of Ls or Lb.  Choose your L such that the maximum 
allowable working pressure, Pa, for each failure mode is approximately 
identical.  i.e. you want Pa from 6.19.5.1 to be equal to Pa from 6.19.5.2, to 
be equal to Pa from 6.19.13, etc.  If you have a target working depth for your 
design, apply your own desired safety factor to that, and then modify your 
hull geometry to achieve that value as your Pa.  The usage factor multipliers 
for the limit pressures for each mode of failure ensure that the theoretical 
failure of your hull will occur by inter-stiffener strength failure.




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