design considerations for aluminum hull structures - Ship Structure ...

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-54-000000000Bottom Shell PlateSide Shell PlateDeck PlateTank Top PlateWing Bulkhead Plate (Upper and Lower)Inner Bottom Floor and Girder PlatesBottom LongitudinalDeck LongitudinalTank Top Longitudinal00Other Hull FramingStanchionsMembersIn general, — these criteria will establish minimum scantlings to resist combinationsof primary and secondary stresses, local loads, impact, abrasion, slamming, etc.,with consideration given to vibration and buckling problems. Tt will often benecessary to increase these minimum scantlings to suit hull section modulusrequirements.Design Criteria for Plates - In gene~al, the approach to converting steelplate thicknesses to equivalent aluminum thicknesses requires the derivationof an “effective” steel thickness by deducting all corrosion or abrasion allowances,then increasing this thickness by a function of the relative strengthratios, and adding back any required corrosion or abrasion allowances.The corrosion allowance to be deducted from steel will depend upon itsanticipated exposure to salt water. An allowance of I/8 inch or 10 per centof the thickness, whichever is less, is proposed for the hull envelope (deck,side and bottom plate) with a 1/16 inch allowance for the internal plates.If the owner or Regulatory Bodies have added an additional margin for abrasion,such as on the flat of bottom or on the bottom of the hold, this should alsobe deducted.The factor by which the “effectivelythickness is to be modified is basedupon the ratio of the sum of the welded yield and ultimate tensile strengthsof the materials as in.Equation (1) previously. For plates loaded primarilyin shea~, tension or compression, the full ~atio should be used. However, forplates which are loaded primarily in tertiary bending (bending betweer stiffnersdue to applied normal load) the square root of this ratio should be used, sincethe section modulus of an element.of plate is a function of (thickness)2. Forplates subjected to a combination of tertiary bendfng and tension, compressionor shears an average factor should be used.The allowance for abrasion to be added back to the resultant aluminumthiclmess is somewhat arbitrary. Howeverj the previous discussion of aluminumalloy abrasion resistance indicates that aluminum will abraid about 4 timesas fast as steel in a similar environment. Thus, for equal life, the steelallowance should be multiplied by four, unless a detailed economic analysis
-55-indicates that it is less expensive to renew the Platep~ovide steel chafing bars. However, neither o? theseeconomically or technically attractive at this time.periodically or toapproaches is consideredSummarizing the foregoing cliscussion,the conversion of mild steel pla’:ethicknesses to .&minum would be as shown in Equation (3):m97,000 n +~cEquation (3): talum ‘ ‘steel“cl “2 y+u 2(Where talum = minimum required aluminum thicknesststeel = steel thiclmess required by MS fileswithout correction for corrosion controlor increases for hull girder sectionmodulus requirementsc1 = corrosion allowance for mild steelC2 = additional allowance for abrasionY, U are as defined fo~Equa%ion (1)n is an exponent based on type of stress such asbending, shear or axialValues of Cl, C2, and n are as follows:Itemc1’32 nMinimum bottom thicl-mess I/81’or .lOt As required by Owner 1Side Plate I/8’!or .lOt o 1Deck Plate (exposed)Determined primarily by hull girder S.M.requirements. Equation (3) not applicable.Tank Top Plate “1/16“ As required by Owner 3/4or AmUpper Wing Bulkhead Plate. 1/16!1 o 3/4Lower Wing Bulkhead Plate 1/16“ As required by Owner 3/nor AMFloors and Girders 1/16!! o 1Shell Plates at Ends I/8° or .lOt o 1/2In addition ‘cothe foregoing, a safe-tyfactor of 1.2g on the critical panelbuckling strength is recommended. The panel buckling analysis can be based uponthe primary hull bend~ng stress without considering the additional stress fromsecondary bending of the plate-s-tiffenercombination, since the la%ter isgenerally,quite small. For an aluminum hull equivalent to the M/V CHALLENGER,fabricated with 5083 alloy, this maximum hull bending stress willbe 13.~ KSI
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CONTENTSI.. II.III.Iv.v.VI ●VII.I
Page 9 and 10:
LIST OF FIGURES(Cent’d)FIGURE NO.
Page 11 and 12:
I. INTRODUCTIONThis report summariz
Page 13: art in fabricating and maintaining
Page 16 and 17: MONTEROSSO GRANA /17VALGRANA / CARA
Page 18 and 19: -8-Numerous references have been re
Page 20 and 21: .10.TABLE 2. Mechanical Properties
Page 22 and 23: TABLE 2 Mechanical Properties of Al
Page 24 and 25: TABLE 3 Mechanical Property Limits
Page 26 and 27: -16-l?igures5, 6, 7 ati 8 present f
Page 28 and 29: -18-ti-’”’-”-””””-L
Page 30 and 31: -20-60 .r---.— ..,.— -——,L-
Page 32 and 33: .22-each stress level, rate of load
Page 34 and 35: -24-!Z456-H321 = 0.485083-H321 = 0.
Page 36 and 37: -26-(c)Members with partial or cont
Page 38 and 39: -28-AllOyS 5083 and 54.56(~ content
Page 40 and 41: -30-The previous paragraphs have de
Page 42 and 43: -32-The problem of cargo hold abras
Page 44 and 45: -34-The question of residual stress
Page 46 and 47: .36-Each alloy was given a relative
Page 48 and 49: -38-GENERAL OBSERVATIONSFYior to a
Page 50 and 51: -40-The question of comparative imp
Page 52 and 53: -42-(d)(e)Poor quality welds due to
Page 54 and 55: -44-The ABS criteria noted above we
Page 56 and 57: -46-DNV would consider fatigue in e
Page 58 and 59: -48-is less, for the exposed side s
Page 60 and 61: Equation (2):-50-Hu1l SMa~um = Hull
Page 62 and 63: -52-Another aspect of vibrations wh
Page 66 and 67: -56-at the deck and keel. This stre
Page 68 and 69: -58-AT is the change inUT= Thermal
Page 70 and 71: -60-SUl@!ARYAll parties contacted f
Page 72 and 73: -62-(c)(d)(e)(f)T~e exterior side o
Page 74 and 75: TABLE 12 Aluminum Bulk Carrier - Su
Page 76 and 77: .66-INSUT.ATION AND SHEATHINGShell8
Page 78 and 79: -68-(b)(c)(d)(e)(f)(g)(h)(i)(j)At l
Page 80 and 81: -70-IIF.INSTALLATION OF SYSTEMS AND
Page 82 and 83: Rudder Assembly -carrier should be
Page 84 and 85: -74-(b)MechanicalTensile Strength 6
Page 86 and 87: -76-(e)The steel piping must be of
Page 88 and 89: -78-Other Piping Systems and Valves
Page 90 and 91: -80-struetion for the aluminum hull
Page 92 and 93: -82-Large heavy type machine~ must
Page 94 and 95: suffers attack in an alkaline envir
Page 96 and 97: -86-REPAIRSObtaining proper repairs
Page 98 and 99: -88-The design of the midship s~cti
Page 100 and 101: -90-assuming the increase is applic
Page 102 and 103: LIGHT SHIP WEIGHT ESTIMATE-92-In or
Page 104 and 105: -94-TABLE 20 Aluminum Bulk Carrier
Page 106 and 107: TABLE 22 Trim and StabilityFull Loa
Page 108 and 109: -98-TABLE 24 Price of Steel Bulk Ca
Page 110 and 111: GaseNumber. . . -.,- .TABLE 27 Comp
Page 112 and 113: -1o2-TABLE 28CarriersComparison of
Page 114 and 115:
12 ---n..T.[T7%l,=LEGS IU ORF=ErY
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-106-such as iron ore, on two of th
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-108-7)is,zg~ gg~5e mzz~E’4E!~K2j
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-11o-(a)(b)(c)(d)Inerting system fo
Page 122 and 123:
-112-fatigue, particularly in the p
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-114-2k* Installation of Systems an
Page 126 and 127:
-116-LIST OF REFERENCES(7)Fatigue P
Page 128 and 129:
-11.8-LLST OF REFERENCES(Cent’d)(
Page 130 and 131:
-120-ADDITIONAL SOURCES OF INFORMAT
Page 132 and 133:
-122-redistribution of the still wa
Page 134 and 135:
-124-APPENDIX BEXCERPTS FROMRULES A
Page 136 and 137:
-126-92.07-10(d)(~) Interior stairs
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-128-~gE1+0102030- .. ..—405060
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ectintyclassification4KEYWORDSROLEL
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SHIP STRUCTURE COMMITTEE PUBLICATIO
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