study of ship framin.jan.1990.t-r

7/28/2019 Study of Ship Framin.jan.1990.T-R

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TABLE OF CONTENTS

I. INTRODUCTION

11. THE SHIPS HULL

III. FRAMING SYSTEMS

IV. PLATING STRENGTHa. Normal Loadb. Coplanar Compressive Load

v. TYPICAL EXAMPLES OF SHIP FRAMING SYSTEMSVI. REFERENCES

?AGE1

1

223

J

26


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STUDY OF SHIP FRAMING SYSTEMS

I. INTRODUCTION

11.

The idea for this study was generated by readingreference 1*. In this publication the author analyzea thebasic principle of plating strength which may be applied tothe design of framing systems. However, the importantfactors of ,interior space utilization, weight and costsavings, producibility and maintenance, in general, are notconsidered or examined for the benefit of the ship designer.References 2 and 3, which are among the mostauthoritative treatiaes in ship design, deal with the topiconly cursorily and are of little help in the selection ofthe moat convenient framing system.

THE SHIPS HULLThe hull of a ship may be likened to a slender,watertight, container with fined ends. This container islike a hollow box-girder of varying cross section along itslength which ie acted upon by forces, corresponding to thevarious ship weights and the action of the seaway. The

aggregate Of these fOrCee constitutes the loading. TO re~iatthis loading the hull must have adequate strength. Thegreater part of the hull strength is provided by plating,stiffened and supported by various structural shapee. Thelatter structural members when properly oriented accountfor a minority of the total hull strength and weight.but are crucial to.the ability of thk plating toresist ,the loading. The structural shapes associated withthe hull plating uake up the framing.

111. FRAMING SYSTEMSA description of the historical development of framingsyatema with numerous .illustrationa may be found inreference 1.The lightest and more closely-spaced aet of stiffenersattached to a gross panel of plating characterize theframing ayatem even though, this set ia supported by heavier

more widely - epaced stiffeners at right angles.A longitudinal framing system has the moreclosely-spaced set of stiffeners oriented fore-and-aft andthe individual stiffeners of this aet are calledlongitudinal.A transverse framing system haa the more closely-spacedaet of stiffeners oriented athwartahip and the individualstiffeners are called frames.

*References listed under Section VI. ,


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-2-In the evaluation that follows we will considerlongitudinal and transverse framing systems for thelongitudinally effective gross panels of plating such asdecks , side shell and bottom plating.The choice of framing systems is governed principallyby the strength requirements, especially longitudinalstrength, but in addition some of the following factors mayhave to be considered:a) Ease of csrgo handling.b) . Interior space utilization.c) Transmission of Ioadg from one structural componentto the rest of the hull.d) Effective structural connections.e) Local load requirements such aa ice losda, locktransiting, tug action, etc.f) Ease of construction, cleaning and maintenance.

IV. PLATING STRENGTHThe ships hull is a complex of reinforced gross panelsof plating. The evaluation of the overall 9tructuralstrength of the hull i9 a rather involved operation which isbeyond the scope ofthis publication.Reference 1 deals exhaustively with the strength ofstiffened gro99 panels subject to lateral and coplanar.(in-plane) compressive loads.To simplify the problem of plated structures strengthevaluations we will consider individual panels of plating9ubject separately tbfiormal and coplanar loads.

a) NORMAL LOAD

FIGURE 1. Plating of panel subject to normal load.In Figure l.we have a panel of plating 9ubject to

normal 10ad. The. geometry of shipa hull plated structuresis such that the ratio a/b i9 generally greater than three.For this case the plate bending stress is given by thefollowing expre9ei0n.


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-3-

~=kp (+)2where,~= plate bending stre99, p9i

k= constant depending on the support condition of theedges and the point location.P- pre9aure, psib- short side of panel, in.t= plate thick nese, in.

The previnus equation Indicatea that the plate bending9treaa for normal. load Is heavily dependent on the b/tratio. Panela of plating 9uch a9 the one illustrated inFigure 1 are generally considered to be edge-fixed in hullstructures. Except for the girthwise location of this panelof plating, there is not much difference in the strengthcondftion whether it corresponds to a longitudinally ortran9veraely framed gro9a panel of plating.

b. COPLANAR COMPRESSIVE LOAD

8I Typical panel nf plating of a transversley framed ship.Typical panel of plating of a longitudinally framedship.

FIGURE 2. Panela of plating subject to compreaaive coplanarlaada.


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-4-

DDS 110= DDS lI

9

zx1L&.z

.s+m$ ,..-mm

: ~.5a

o 100 150BREADTH-THI%NESS RATIO, b/t OR K12(b/t),


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-5-

DDS IIH DDS XlFIGURE 4.

PLATE BUCKLING STRESS~MPRESSION COEFflCIENT~R USEWl~ RGURE\fI

o .10 .20 :30 40 50 60 70 so .90 ~100SIDE RATIO, b/a


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-6-

For the panels of Figure 2 let us assume that theuaterial is medium steel (MS) and that the thickness iet = l/2in.

For panel~we may use attached Figures 3 and 4 frOmUnited States Navy Deeign Data Sheets, USN DDS, 1100-3.

From Figure !-4:b/a = 0.25, K12 -

From Figure 3:K12 b/t =buckling stressccr

1.a85

1.885 x 60 = 113.1, therefore critical= 8,300 paiFor panel2 using Figure 3 bit = 60, therefore criticalbuckling strese cc= = 27,000 psiWe can establish the following ratio:buckling stress for panel 2 27 000= ~ = 3.25buckling etress for panel 1 ,The foregoing indicates that the buckling straas for a

tYPical Panel Of Plating Of a longitudinally framed ship iaover three times that corresponding to a tranaveraaly framedship.With referenca to this comparison three additionalfacta need to be stated:A. The inherent welding distortion in the bottomplating of a.tranaversaly framed 9hip wil

aggravate the relative weakneaa of panel dB.

9The geometries of panel@ and 2 have been aaaumedequal. In reality, the ratio b a for a tranavaraelyframed ship will generally be smaller than 0.25.This will in effect make the buckling stress ofpanel~ 9maller than 8,300 psi.

c. For the ca9e of the longitudinally framed ship whenwe conaidar the real hull 9tructura whichcontributes to longitudinal 9trangth we a190 have,in addition to the panela of plating, the


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-?-longitudinals which border and support the panelsof plating. The cross sections of theselongitudinal provide additional area whichincrease the section modulus of the hull girder,thus reducing the level of the longitudinal bendingstreeaea.

v. TYPICAL EXAMPLES OF SHIP FRAMING SYSTEMSIn thie Section the midship sections of eix typicalahipa are praaented. Theee will serve as a basis for thediecuasion on advantages, diaadvantagea andjustificatlonsfor the eelection of tranaverae or longitudinal framingeyatems. For this purpose the gross panela of plating whichmake up the longitudinal hull structure are analyzedseparately.

The midship eectiona are the following:a. Break bulk cargo shipb. Container9hipc. Roll-on/roll-off shipd. Genaral purpose bulk carriere. Bulk carrier with deep double bottomf. TankerIt i9 obvious that thera ara many other typee of ahipathat could be considered. Aleo, even for the aix midshipsection9 presented there could be numerous alternative in

the arrangement of the principal 9trength membere. However,it.is hoped that the analyaie of these six midship sectionsin the cho9en tabular form will help the designer inselecting the appropriate framing syacem for each particularapplication.It need9 to be emphasized that the eix midship aectfonspresented here serve as the basia for this study and are notco be construed in all caaee aa the recommended choice offraming syateme.It will aleobe obvioue by observing the aix typical

midship sections that a purely traneverae or longitudinaley9tem of framing does not exist for any type of ship.Kathar, for a given type of ship one can observe varyingdegrees of combination of tran9verae and longitudinalsyetema of framing.


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__-r--r---- --------------------- - --------- .. ..._ ..

;-t-f; .v.TAG.+:--=-:-J:=Significant contribution to longi-I tudiml strength,especially:1~ ~resistmce to buckltig.d i

1--------------------------------------------------------io:e---------------------------------3 ~ 2. DISAOV&NTAGF kss of si~ificant contribution to! longitudiml strength., If welding ~i~l

Idistortion is uncontrolled it myg

1;;,1 I trigger buckling at low compressive Iatrese.------------------0 ---------------------------------------------------------------------------& JUSTIFICATION It provides bottom landing for aide No interferencewith stomge sincem 13. frames. I the double bottom carries only liq-D0$

uids.

d0k 1. ADVNTAGP Improved stowage. Better local In pnrtiona removed from the neutral.u strength for m- gation amngst ice,z

axis, the contribution to longitude-

ilock transiting, et.. Transtits ml strength my be significant.deck lads donward better (frms

kl I1

Iacting as colms) .R -----------------------------------------------------------------------------------------:---DISADVANTAGE Los es contribution to longitudiml ] Impaired stonge because of webX , ,,2.

!~ ~~~~ha~e~gions r~ved from I frames.More.penetrations complicateItil I fitting,,welding,and painting.1

9 ~----------------------------:-----:-------:------------1~1 E 13. 1--------------------------------------

JIIST1ICATION Decks are mre closely spaced thanmlmli

I transverse bulkhmds, therefOre, t:]elame as advantages.I span for lateral loading is smiler, 1~l.~ I I --


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--rI

---------- ------- -2. DISAOVANTAGEHi81xlM ------------------~ ,3. JllSTIFICATION

It. ~VANTAGE

I------------------dISADVANTAGE12.

------------------g 13. JUSTIFICATIONSt ~I II I

---- . _____mANSVFRSE SVSTEM

- -Improved stowage.

------------------------------------&ss of si~ificant contr.tiutionolongitudiul strength.

-- -- -- -- -- . -- -- -- -- -- --- -- -- -- --- -- -Transmits column load better totransverse side frames. If thedeckis extra thick because of wide hatch.es, bwkling MY not be of concern.

Improved stowge.

I

- ______IOFIGI,PInINAl,SYSTFH }---- ________ 1

Significant contribution to longi- Itudiml strength.

~I-------------------------------------

Im~ired stiwage. Ii/

-------------------------------------- /,@d connections with stiffeners in Itransverse bulkheads. 1:

IContributes to longitu~iml strength ISsp.eciallyif removed from neutral Iaxis.

I,----------------------------------- /-------------------------------------- ilo contribution to longitudinal I Imwired stowage.]trength. ~ :iI I-------------------------------- --- ---------------------------------------------------------------------------bouthe same as per upper deck. /~me as per upper deck.

1 /I !


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1I m.- . .jl 318 [N. PL (TYP) n

Lpp=492-?, Lw=~5-O, &u&w= 75-0,D=43-6,T(q=3t-#


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_T __

TRANSVFRSE SYSTEM MW~TllnINAI, SYSTFM-

~VANTAGE None.I.

I Significant contribution to longi-I tudinal strength.I

111

1,~ ---------------------------------------------------------------------------------------------8 2. DISAOVANTAGF tiss of significant contribution toI:lh[ None.:1 I longitudinal strength. If welding Idistortion is uncontrolled it may I

~ElIil I trigger buckling at low compressive ~Istress. I------------------8 ------------------------------------ --------------------------------------Justification It provides bottom landing for side No interference with stowage since:1 m 13. frames.~1 I the double bottom carries only liq-gl

t ;

uids.

; ~tiNone.

f . VWTAGEI Significant contribution to longi-tudinal strength as part of the heav!gunwale box girder.IE IIu I----------------- ---------:--------------------------- /--------------------------------------1 ~ 12. lSADVANTAGEbss of significant contribution to I None, since frafing is in void spaceIi I lorigitudi~l strength. I (no interference).I 1.mlmi 1------------------ ---------------------: --------------- ------ . ----, ---------------------------13. JIISTIFICATION1~~~1 No jugtification for this gtrake. Due to small extent of upper deck,I framing contribution to longitudimlI strength ia veq im~rtant.18 I ,1 I

I

1


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I--- - - __________ .....~II,.....~...l~.._ -------------

I il. 4nVANTA(;;Il I III1----------------:.l?. nlSAllVbhlTA(:FII

l-------------_----1~. , lIISTI}. ICATIO}III1

I I I----- ----

.------ -------------------- ------

------ .-___..__ -_____ .--_-__ ---?-----________________TPAFISVFPSE SVS,rFM [#a}lc,rllllFlm[,ysl$FMAssociated wit!--

--------..---.-..__................. ISide stringersare more closely Co]ltj:ibutionto 10I1Ytudi]]ilstrc~lrjt]!sl>acedthan transverse bulkheads, ! relatively smll because f [>roximity[therefore, the spn for lateral I to ~~t~~l a~i~. 1loading is smiler.heavy gunwale box girder and side I Iweb provides needed rackingstrengthj------------------------.------------l----------.----.----------.-_-_---_---/kss of smll contribution to longi-1 No contribution to racking strength Itudinal strenqth. I and supl>ortof heavy gunwale box Ii girder.

I------------------------------------i--------------------------------------With the addition Of side WebS, prO-l None.vides god sup~rt for heavy gunwalelbox girder. I- ___ I- ------None. i Significant contribution to longi-~ tudinal strength.

I------------------------------------l----------------USS Of significant contribution to [ None, since framing is i vOidlongitudinal strength. I (no interference).I1------------------------------.----- --------------------------------------I Same as advantage.1

IIII I--. ___ _______________ -_


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BOTIOM 0.89 IN. Slm mmlNN~ S0T70M 0.60 N, WW WRW 1.18w

Lw= 719-0, LPP=675-O,(wm=95-O,b.~: 41 SIDE)u54-0T- =31-O,A=B,8OOG.TON


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-SV~SE SYSTFA mNGITIIDINAL SYSTEM

1. AOVANTAGE None. Significant contribution to longi-tudiml strength.u~$ ------------------------------------------------------- --------------------------------------2, DISAOVANTAGRQ Loss of significant contribution None.~ to longitudiml strength. If$ g welding distortion is uncontrolledh & it my trigger buckling at lowo z compressive stress.m

E-------------------------------------------------------- --------------------------------------zZ 3, JUSTIFICATION It provides bottom landing for No interferencewith stowage since

& side frams the double bottom carries only liq-2 I uids.i;;ZY--i;-~~~;-;-~-C;;;;;;;;Gi~-2;;;;5-2;Si;-g~C~&-ZE-ZgGG;-------7-----7-y----------T-----his ls def~nltely undesirablew or a shiD of this SiZe.and requires special considerationunder ABS rle~.; 1. fVANTAGE Transmits deck lads downward bette

.1

On ~rtions removed from neutral axisX (frames acting as columns). the contribution to longitudinalE strength my be significant.u~g

------------------I-------------------------------------------------------------------. DXSAOVANTAGE Loss of contribution to longitud- Impeired stowage because of webinal strength in regions removed frames.b 3 from neutral axis.~ g

~ ------------------------------------------------------- -------------------------------------a : 3. sTIF1cAT1oN Decks are more closely s~ced then Same as advantages.A transverse bulkheads, therefore, I8 the span for lateral loading is

I . .smeller.

..


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--.-_r__ _

~

---. --- _: ________

TRA}ISVFBS F SYSTEP1---- t ~- -1. MVANTAGEI

For a given bween deck heighta11OWS la,rge~head room, if webframes are not otherwise required.Depends on traffic patterns, i.e.,ramp arrangements.i

------------------ ------: ------------------------------2. DISAOVBNTAGR Nocontribution to longitudinalI strength..

g ~S .,f l. 1-----------------------------------------------------JIISTIPICATION *me aa per advantage.I1

1. AOVANTAGEISame as per upper deck..

i, .,, 1------------------:1---------------------------. DISADVANTAGE Same as per upper deck.1j~: [ ;-----------------8

.7[)sTIFICAT10N1.I!

. -- . ---------, --------- ---------------In figure 8 the 4th deck showstransverse framing chosen probablyto improve head room for a giventween deck height.

Significant contribution to longi- 1tudinal strength. II

I--------------- ,---------------------- IIf web frames are not otherwiserequired, a giveq deck height will /result: in.smiler head room. I,--------------- ---------------------- IIsame as:advantage.

1:

Contributes to longitudinal strength,iespecially if removed ,from neutral Iaxis. I!-----------------------------Same as per upper deck. I1I

,/--------------- .----------------------In figure 8 the 2nd and 3rd deck, Iwhich probably required deep beams aslweb frame components, show logitdi-1m 1 framing. the longitudinal wouldlbe spanning the shortest distance in Itheir SUPPort of wheel loadiqs. I


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-16-

8IIIi

III1

18.02, ., %.6 LB rl -,Cf 18s4.2 w,. % co c,

(0)W TWSV wEB FWE(- em-3MJ


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I[---y ~------- - .-- - -,-WA}ISVFRS E SYSTFM [.3 P1GI,PIIIIINA[. SVSTFP/

h

iIlI : t 1. MVANTAGE ~ None.

_____}__ ------------: ,1 Significant contribution to Longi- \

1:21 I[g~~ /1 tudiml strength. I

I1%11 IIm {----------------- - -------- ------------ ----------------- --------------------------------------I8 # 2, DIS~VANTAGF Ibss of significant contribution to None. :~g,~ ;[ 1 longitudiml strength. /la I 1

1!11% III I1 I----------------------------------------------------------1! Provides tittom landing for side /J(ISTIFICATION No interference with stowage since 11: I 13. frames. 1 dotile bottom carries liquids. 1

1~~~ II 1Ig I3 .1

- ___1. ~VANTAGF Provides efficient connections be-& I Small,contribution to longitudinaltween upper wing bnks and lowerz I strength.-nks. 1

II II1

I /------------------ ---------- -------------------------- I -------------------------------------- /Since this plating is close to the I Interferes with wloading of solid IIi I 12 lsAnvANTAGE neutral axis, the loss of contri- ] cargo and liquids. The drain holes Iw 51 I bution to longitudiml strengthis I get clogged and are subject toI almst nil.1~1~~.

{I ewessive corrosion.I

& ------------------ ------------------------------------ --------------------------------------.,~ ~ ~ ~~. ,IIISTIFICATION These are the only frams inside %me as per advantige. I~ the cargo holds, and being vertical I!B ,

I \ do not interfere with cleaning. IIl. I l--- I

--- . . . . .


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r___II

uE13.{ISTIFICATIOP-------.---.---.--

I$[n1------------------~ 12. ISMVANTAGE

i1. ~VWTAGE1---------- --------

DISADVANTAGE12.I-----------------,~3. JUSTIFICATION

, I

------ -- ____WANS,VFRS F SVSTFM

-_ _______Lighter cargo when carried in upperwing tanks is easier to unload.

,------------------------------------No contribution to longitudimlstrength..

------------------ -------- ----------Same aa per advantage.

---------------------------- --------

------------------------------------

___ - ___l~n$l~ I,PID I}IA1, SYSTFM

-. -_-_. --_ _________Significant contribution to long:tudiml strength.

-------------------------------------*W as per side shell.

------------------------------------- .%me as per advantage.

_

,-------------------------------------

-------------------------------------


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-19-

1._

TI. ._._ ._,t.. .-..

*CTION IN WAY OF.. \ WE3 FRAME SECTION INWAYOFOROINARYFRMEPLW*SWuo , ,,,0..,, . . . . . . . -. 1.cs,- , n. ---- .. . . . .,..=-. lK wCS, ,.0S(DC w, , -ZD ~ ,,

I

,.,!,, w. mLOA = 709-0$, L !,PP 673 O , BWOUJ = 10[-s, o{~o,. 594-,.,T (OSW) =37-0, A , 63,200 L~ TON

69. a oceangoing dry bulk carrier with shallow d..bl. bet!i~


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I. L1. MvMTAG~

------------------2. DISMVbNTAGR!

I ----------------- .JIISTIFICATION

13.

1. ADVANTAGE

~ ~ 1------------------,.3. JNSTIFICATIONlm

I

~ANSVERSE SYSTEM

None.

------------------------------------bss of significant contribution tolongitudiml strength.

----------------- -------------------None.

None.

------- -----------------------------No contribution to longitudimlstrength.

------------ ------ A - -------- --------gone.

IONGITIIDINAI,YSTFMSignificant contribution to longi-tudiml strength.

--------------------------------------None.

--------------------------------------same aa per advantage.

On portions r~ved from neutral axiscontribution to longitudiml strength~Y be significant.

--------------------------------------None.

,-------------------------------------- as Per advantage.

I

z

---


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1. MVANTAGE

---------- -------2. DISADVANTAGE

----------------- .3. JUSTIFICATION

1. AOVANTAGF

------------------?. DISADVANTAGE

------------------1. JIISTIFICATION

mANsVFRSE SYSTEM

None.

------------------------------------tiss of significant contribution tolongitudinal strength.

------------------------ ; -----------None.

,-------- ---------------------------

----------------------------------- I

IONGITIlOIIIAI, SYSTFM /

ISignificant contribution to longi- Itudiml strength. II/-------------------------------------

None. I~

--------------------------------------same as per advantige.

IIIi-------------------------------------- /II

------------------------------------- ~III

4N

1


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-22-


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I~ANSVFRSE SYSTEM I I~NGITIIDINALSYSTEM

I1. ~VANTAGR None. I Significant contribution to longi-I tudiml strength.

I I

,1

I I----------------- ---------------------------------------------------------------------------DISAOVAWTACE Loss of significant contributionl! 2. I None.to longitudinal strength. ~

g~l

!gl I

I

------------------------------------------------------ --------------------------------------$

3. JUSTIFICATION None. same as per advantige.

8%.~ 1. AOVANTAGE Cleaning of ti~s is easier., h portions-removed from neutral axisE contribution to longitudinal strength

=Y be significant.z01 I1El ;------------------------------------------------------l-:----------:-------------------------DISADVANTAGE No contribution to longitudinal I Interfereswithtank cleaning.gl .k I strength.

IiIa

~ ; I------------------------------------------------------------------. JUSTIFICATION In ~ller size,vessels (say, below Ssme as per advantige.& :!

! 300 ft. long) the contrfitionto Ilongitudinal strength my not be es-I IhI

sential.I I I


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- ~----- __TRANSVERSE SYSTEM

L1. AnVANTACE I None.

------------------ I-----------------------------------2. nISAOVANTAGE uss of significant contribution toI longitudiml strength.I.1 I------------------t-------------------------------------

3. JllSTIFICATION None.

1. mVANTAGF

I------------------ I------------------------------------!. DISAnVANTAGR~

- __ _ I[flhl~ I-PI lnIFIAI, SysT~M

-- _- _ _______Significant contribution to longi- Itudiml strength. II

.i--------------------------------------None. I

,-------------------------------------same aa Per advantage. I~;iI!------------------------------~II i----------------- ---------------------: --- ------------. JNSTIFICATION I I

i ---~1

I------------------------------1II


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-25-

DECK 1-1/8 IN, PL ,HSS

I DECK LONG. 16 s 1/2 IN, WEB , HSS5-1/8 x 7/8 IN, FkG ,HSS1-. 1-. ~ - --i ,\,

0.625 IN, PL , HSSZ ;& .]~~{l!G.r- -- d_i.0.547 [N. PL I !~ *

~,. 0,S0 IN. PL

1L.. ._

0.547 IN. PL A .(

l.\ ;. _~ , +, f ; -.62S IN. PL ~ I

..;

0.672 IN. K M

t0.735 IN. PL M

0.760 IN. PLM 1.h

- A-

$lOEI IN

i 91x1-3/16 IN. PL,MSS 80TTO~ SHELL 1-1/8 IN. PL , NSS001 LONG. 29- !/2 z 510 IN. WEB , HSS

7-1/16 x 1-1/+ IN FL G,HSS

1-!/8PL, H

SHELPL

LPP =1027-On,w: 1050-On,moJ. 15E-o,=83-81,T [OSW)=54-3,DWT (-} .175,0~ LG TON

fig.0 Mdtip sedi~ of a ta&e, of oboti 175,000 toni dwt


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-26-

VI. REFERENCES1. J. Harvey Evans, Second Cycle Ship Structural DesignConcepts, Chapter 7, Preliminary Choice of FramingSysceme.

2. Shi SNAME 1969, edited byAmelio M. DArcangelo.3. Ship Design and Construction, SNAME 1980, edited byRobert Taggart.

study of ship framin.jan.1990.t-r

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