RULES DET NORSKE VERITAS (DNV) = STRUCTURES = - Boat Design Net

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Amended July 2011, see page 3 Rules for High Speed, Light Craft and Naval Surface Craft, January 2011Pt.3 Ch.3 Sec.7 – Page 35SECTION 7PILLARS AND PILLAR BULKHEADSA. GeneralA 100 Introduction101 In this section requirements for pillars and for bulkhead stiffeners substituting pillars are given.A 200 Definitions201 Symbols:L, B, D, T, C B , see Ch.1.t = thickness of plating in mms = stiffener spacing in m, measured along platel = length of pillars, cross ties, bulkhead stiffeners etc. between effective supports normal to their axis in mI = smallest moment of inertia in cm 4 , including 40 x plate thickness as flange for bulkhead stiffenerA = cross-sectional area in cm 2 , including 40 x plate thickness for bulkhead stiffenerp = design pressure as given in Ch.1.B. PillarsB 100 Arrangement of pillars101 Where practicable, deck pillars are to be located in line with pillars above or below.If arrangement with pillars in line is not possible, deck beams or girders will have to be reinforced.102 Pillars or equivalent supports are to be arranged below deckhouses, windlasses, winches and other heavyweights.103 The engine room casing is to be supported.104 Doubters are to be fitted on deck and inner bottom, except in tanks where doublers are not allowed.Brackets may be used instead of doublers. Where pillar tension may occur, brackets are required.105 Structural reinforcement below pillars will be considered in the individual cases.B 200 Cross-section particulars201 The radius of gyration of a member is to be taken as:I a= moment of inertia as built in cm 4 about the axis perpendicular to the expected direction of bucklingA a = cross-sectional area as built in cm 2 .If the end conditions are different with respect to the principle axes of the member, the i-value may have to bechecked for both axes.B 300 Pillar scantlings301 The cross-sectional area of members subjected to compressive loads is not to be less than:η =Plikk--------------- minimum 0,3 l1 + - iiA==I----- a( c m )A a10 P---------- ( cm 2 )ησ c= axial load in kN as given for various strength members in 302 and 303. Alternatively, P may beobtained from direct stress analysis. See Sec.9 D= length of member in m= radius of gyration in cm= 0.7 in generalDET NORSKE VERITAS AS
Rules for High Speed, Light Craft and Naval Surface Craft, January 2011 Amended July 2011, see page 3Pt.3 Ch.3 Sec.7 – Page 36= 0.6 when design loads are primarily dynamicσ c ==σ E when σ Eσ Fσ F< -----2σ F 1 – --------- 4σ E when σ > -----σ FE 2σ E =σ F = minimum upper yield stress of material in N/mm 2E = modulus of elasticity for aluminium = 69 000 N/mm 2 .The formula given for σ E is based on hinged ends and axial force only.If, in special cases, it is verified that one end can be regarded as fixed, the value of σ E may be multiplied by 2.If it is verified that both ends can be regarded as fixed, the value of σ E may be multiplied by 4.In case of eccentric force additional end moments or additional lateral pressure, the strength member is to bereinforced to withstand bending stresses.302 The nominal axial force in pillars is normally to be taken as:P = n FnFπ 2 iE------------ 2 (N ⁄ mm100 l2 )= number of decks above pillar. In case of a large number of decks (n > 3), a reduction in P will beconsidered based upon a special evaluation of load redistribution= the force contribution in kN from each deck above and supported by the pillar in question given by:F = p A D (kN)p = design pressure on deck as given in Ch.1 Sec.2A D = deck area in m 2 supported by the pillar, normally taken as half the sum of span of girders supported,multiplied by their loading breadth.For centre line pillars supporting hatch end beams (see Fig.1 and Fig.2):A D ==4A ( 1 + A 2 ) b 1---- when transverse beamsB4A ( 3 + A 4 + A 5 ) b 1---- when longitudinalsBb 1= distance from hatch side to craft's side.303 The nominal axial force in cross ties and panting beams is normally to be taken as:P = e b p (kN)ebp= mean value of spans in m on both sides of the cross tie= load breadth in m= the larger of the pressures in kN/m 2 on either side of the cross tie (e.g. for a side tank cross tie, thepressure head on the craft's side may be different from that on the longitudinal bulkhead).B 400 Pillars in tanks401 Hollow pillars are not accepted.402 Where the hydrostatic pressure may give tensile stresses in the pillars and cross members, their sectionalarea is not to be less than:A = 0.07 A dk p t (cm 2 )A dk = deck or side area in m 2 supported by the pillar or cross memberp t = design pressure, p in kN/m 2 giving tensile stress in the pillar.The formula may be used also tension control of panting beams and cross ties in tanks.Doubling plates at ends are not allowed.DET NORSKE VERITAS AS
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RULES DET NORSKE VERITAS (DNV) = STRUCTURES = - Boat Design Net

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