[PSUBS-MAILIST] help interpreting ABS rules

[Alan via Personal_Submersibles]

Jon,
have you looked at what G.L. says about the same issue.
It may give some clarification. (or not)
Alan

Sent from my iPad

> On 22/04/2015, at 7:08 am, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Given that there is copious distinction throughout the document differentiating heavy and non-heavy stiffeners, it could be that non-distinction in the definitions of equation variables means application to both.  I notice that none of the variable definitions referencing stiffeners differentiates between heavy or non-heavy.  What is the effect in the equation of assuming "I" refers to all stiffeners?
> 
> Jon
> 
> 
> +++++++++++++++++++++++++++++++++
> 
> SEAN STEVENSON WROTE:
> 
> I found a bit of time this weekend to work on the hull optimization
> software, and was just revisiting the "Overall Buckling Strength"
> calculation in Section 6/19.13 of the 2014 ABS Rules for Building and
> Classing Underwater Vehicles, Systems and Hyperbaric Facilities, when I
> noticed the following:
> 
> The limit pressure corresponding to the overall buckling mode between
> heavy support members is obtained from the following equation:
> 
> Pn = (E*t/R)*A_1 + E*I*A_2/L*R^3
> 
> The section goes on to define some of those terms, but what caught my
> attention was the "I" in the second term of this equation.  The
> nomenclature "I" does not distinguish between "I" for a heavy stiffener
> or a regular stiffener in the rules - it is contextual.  Given the
> purpose of the section, I had assumed that it meant "I" for a heavy
> stiffener, but the term in question also contains the term "L", or
> distance between stiffeners, which is distinct from "L_c", or distance
> between heavy stiffeners, leading to some ambiguity.  If the second term
> is a correction for stiffness of the section in between heavy
> stiffeners, the "I" could very well be the "I" for a regular stiffener
> in between, but it isn't clear to me.
> 
> Thoughts?
> 
> Sean
> 
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