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<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial>21.13 Heavy
Stiffeners Stiffeners used for purposes of reducing the compartment length Lc
within which overall buckling performance is checked are termed heavy stiffeners
and are to be designed to meet the requirements for heavy stiffeners in
6/21.17.2. </FONT></DIV><BR>
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<FONT size=2 face=Tahoma><B>From:</B> Personal_Submersibles
[mailto:personal_submersibles-bounces@psubs.org] <B>On Behalf Of </B>Jon Wallace
via Personal_Submersibles<BR><B>Sent:</B> Tuesday, April 21, 2015 7:49
PM<BR><B>To:</B> Personal Submersibles General Discussion<BR><B>Subject:</B> Re:
[PSUBS-MAILIST] help interpreting ABS rules<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV class=moz-cite-prefix><BR>Ok, missed the section on calculating "I".
I looked at the doc more tonight and it seems to me that your original
conclusion of using Heavy Stiffeners is correct. Section 19.11 defines
Heavy Stiffeners as the stiffeners to be used for purposes of checking overall
buckling performance. Section 19.13 requires "heavy support members" which
I believe equates to "Heavy Stiffeners". In Section 19.15.2, Lc is used to
calculate "I". Doesn't this all point to using 19.15.2 to calculate "I"
?<BR><BR>Jon<BR><BR><BR>On 4/21/2015 7:48 PM, Sean T Stevenson via
Personal_Submersibles wrote:<BR></DIV>
<BLOCKQUOTE cite=mid:516782a6-fb8b-4742-bd2d-a7f5369b0708@email.android.com
type="cite">
<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 <A class=moz-txt-link-rfc2396E
href="mailto:personal_submersibles@psubs.org"><personal_submersibles@psubs.org></A>
wrote:
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0pt 0pt 0pt 0.8ex; BORDER-LEFT: rgb(204,204,204) 1px solid"><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?
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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