<html><head></head><body><p dir="ltr">"I" is calculated differently for non-heavy stiffeners (19.15.1(d)) than for heavy stiffeners (19.15.2(d)). It is entirely contextual as to which "I" to use.</p>
<p dir="ltr">Sean<br>
</p>
<br><br><div class="gmail_quote">On April 21, 2015 1:08:02 PM MDT, Jon Wallace via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<pre class="k9mail">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?<br /><br />Jon<br /><br /><br />+++++++++++++++++++++++++++++++++<br /><br />SEAN STEVENSON WROTE:<br /><br />I found a bit of time this weekend to work on the hull optimization<br />software, and was just revisiting the "Overall Buckling Strength"<br />calculation in Section 6/19.13 of the 2014 ABS Rules for Building and<br />Classing Underwater Vehicles, Systems and Hyperbaric Facilities, when I<br />noticed the following:<br /><br />The limit pressure corresponding to the overall buckling mode between<br />heavy support members is obtained from the following
equation:<br /><br />Pn = (E*t/R)*A_1 + E*I*A_2/L*R^3<br /><br />The section goes on to define some of those terms, but what caught my<br />attention was the "I" in the second term of this equation. The<br />nomenclature "I" does not distinguish between "I" for a heavy stiffener<br />or a regular stiffener in the rules - it is contextual. Given the<br />purpose of the section, I had assumed that it meant "I" for a heavy<br />stiffener, but the term in question also contains the term "L", or<br />distance between stiffeners, which is distinct from "L_c", or distance<br />between heavy stiffeners, leading to some ambiguity. If the second term<br />is a correction for stiffness of the section in between heavy<br />stiffeners, the "I" could very well be the "I" for a regular stiffener<br />in between, but it isn't clear to me.<br /><br />Thoughts?<br /><br />Sean<br /><br /><hr /><br />Personal_Submersibles mailing list<br />Personal_Submersibles@psubs.org<br /><a
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