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

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-44-The ABS criteria noted above were used in the preparation of a preliminarymidship section for an aluminum bulk carrier. The resultant weightper foot was approfiately!% per cent of that of an equivalent steel hull,while huu gtider deflections would be,increased by a factor of 1.75.l)urln~the desi~n of the Fast Jkplqyment Logistic (FDL} GhLpS, one ofthe criteria developed and approved by ABS for aluminum deckhouceo wag a~follow~:(a) For plating designed primarily for lateral loading fromwave slap, deck loads, etc.:‘alum =.9 TsteelII/‘TssteelUTSalum(b)For plating designed primarily for edge loading as mightbe induced by longitudinal bending or axial loads:Talm = ●9 ‘steel(UTS)steelUTSalum(c)Framiti
-45-These criteria with some modifications have been adopted into Lloyd’slatest Rules for AluminumYachts, Reference (52), which require a Is per centincrease in plate thickness and a 70 per cent increase in stiffener sectionmodulus when substituting aluminum alloy for steel. These rules apply toaluminum alloys with a 0.1 per cent proof stress of 8 tons/in.2, an ultimatetensile strength of 17 tons/in.2 and an elongation in a 2 inch and 8 inchgage length of 12 and 10 per cent respectively.The Lloyd’s Rules relative to aluminum deckhouses require the followingincreases in scantlings:Fronts, sides, aft ends and unsheathed decksSheathed deckBeams and stiffenersScantlings of small isolated houses20 per cent10 per cent70 per centO per centThese requirements are consistent with those discussed previously, and reflecta consideration of ratios of ultimate strength.Recent discussions with Lloydls relating specifically to the AluminumBulk Carrier project resulted in the following observations:(a)(b)(c)(d)(e)(f)A reduction in steel section modulus of ~ per cent should beaccepted as a basis for converting to aluminum.Consideration must be given to low-cycle fatigue properties inrelation to the hull’s life cycle stress spectrum.Extensive radiographing of welds will be required to ensureproper reliability. Butts should be staggered as much aspossible.Notch toughness is not considered a problem, and no crackarresting riveted seams are required.Hull girder deflection should generally not exceed that of asteel hull of equal length but with an L/D ratio of 16, i.e.,r = SMsteelalumx .95 x 3 x half-depth of ship. This requirementmight be modified for this speciffc case, though both wave andstill mater deflection must be considered.Deflection of local aluminum beams may be SO per cent greaterthan that of equivalent steel section.Det Norske Veritas - DNV has no rules ralating diractly to aluminumstructure at this time. However, they indicate that the procedures usedin selecting high strength steel scantlings would be applicable to aluminum.These requirements’convertmild steel scantlings to high strength steel bya factor which is based upon the ratio of yield strengths. Ultimate tensilestrengths do not enter into the conversion directly, though lower limits areplaced on the ratio of ultimate tensile strength to yield strength. Foraluminum alloys, they would consider both ultimate and yield tensile strengthratios, assuming welded strengths of aluminum alloys, and the entire areaunder the stress-strain cuwe. They would deduct an appropriate corrosionallowance frcm the steel scantlings before converting, and would not requirea corrosion allowance for aluminum. They would also not require rivetedcrack arresting seams for an aluminum hull.
Page 5: 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 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 64 and 65: -54-000000000Bottom Shell PlateSide
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
Page 116 and 117:
-106-such as iron ore, on two of th
Page 118 and 119:
-108-7)is,zg~ gg~5e mzz~E’4E!~K2j
Page 120 and 121:
-11o-(a)(b)(c)(d)Inerting system fo
Page 122 and 123:
-112-fatigue, particularly in the p
Page 124 and 125:
-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
Page 138 and 139:
-128-~gE1+0102030- .. ..—405060
Page 140 and 141:
ectintyclassification4KEYWORDSROLEL
Page 142:
SHIP STRUCTURE COMMITTEE PUBLICATIO
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