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.1 Sec.2 – Page 13The hull type factor k h is an estimate for correction of the vertical acceleration depending on the different typesof hull forms.205 When V ⁄ L < 3:a cg=6 H S------ V0.85 + 0.35------- g0 ( m ⁄ s 2 )L L206 Unless other values are justified by calculations according to accepted theories, model tests or full scalemeasurements, the speed reductions implied by 204 and 205 shall be applied. For SWATH and craft with foilassisted hull, accelerations shall normally be determined in accordance with the above direct methods.207 Relationships between allowable speed and significant wave height will be stated in the “Appendix toClassification Certificate”.2.4k v2.00.41.61.20.8AP 0.2L 0.4L 0.6L 0.8L FPMidshipFig. 2Longitudinal distribution factor for vertical design accelerationB 300 Horizontal accelerations301 The craft shall be designed for a longitudinal (surge) acceleration not less thana l=2.5 C W------- 0.85 + 0.25-------V 2 gL L0-------Vneed not be taken greater than 4LTentative formula for the relation between instantaneous values of a l , H S and V:a l ( 1.67) H S= ------ 0.85 + 0.35-------V 2 gL L0a l is intended for calculation of forward directed inertia forces and may have to be increased based on theoverall impact possibilities in craft’s front.a l may be simultaneous with downward vertical inertia in forebody.302 It may be necessary to pay attention to transverse acceleration from forced roll in bow seas.Period of forced roll to be taken:LT R = ---------------------------------------1.05 + 0.175-------V ( s)LDET NORSKE VERITAS AS
Rules for High Speed, Light Craft and Naval Surface Craft, January 2011 Amended July 2011, see page 3Pt.3 Ch.1 Sec.2 – Page 14V------- need not be taken greater than 4LMaximum roll inclination:Resulting transverse acceleration:a tθ r=π h--------- w(radians)2L= 2-------π 2 θ T R r r r ( m ⁄ s 2 )Static component g 0 sin θ r to be added, when above axis of roll.h w = maximum wave height in which 70% of maximum service speed will be maintained, minimum 0.6 C wr r = height above axis of roll.Axis of roll to be taken— at waterline for twin hull craft— at D/2 for monohull craft.C. Pressures and ForcesC 100 General101 The external and internal pressures and forces considered to influence the scantlings of stiffened panelsare:— static and dynamic sea pressures— static and dynamic pressures from liquids in a tank— static and dynamic loads from dry cargoes, stores and equipment.102 The design sea pressures are assumed to be acting on the craft’s outer panels at full draught.103 The internal pressures are given for the panel in question irrespectively of possible simultaneous pressurefrom the opposite side.104 The bottom structure, forebody side/bow structure and flat cross structures shall be strengthened to resistthe effects of slamming and impact.105 The gravity and acceleration forces from heavy units of cargo and equipment may influence thescantlings of primary strength members.C 200 Slamming pressure on bottom201 The design slamming pressure on bottom of craft with speed V ⁄ L ≥ 3 shall be taken as:k l = longitudinal distribution factor from Fig. 3n = number of hulls, 1 for monohulls, 2 for catamarans. Trimarans and other multihulls will be speciallyconsidered.A = design load area for element considered in m 2 .For plating A shall not be taken greater than 2.5 s 2 .For stiffener and girder A is taken as the product:spacing x spanA need not for any structure be taken less than 0.002 Δ T --T OP sl 1.3k Δl------ 0.3 0.7T 50 – β x=nAO------------------- a50 – β cg ( kN ⁄ m 2 )cg= draught at L/2 in m at normal operation condition at service speedΔ = fully loaded displacement in tonnes in salt water on draught Tβ x = deadrise angle in degrees at transverse section considered (minimum 10°, maximum30 °)β cg = deadrise angle in degrees at LCG (minimum 10°, maximum 30°)a cg = design vertical acceleration at LCG from B200 (a V calculated at LCG).DET NORSKE VERITAS AS
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RULES DET NORSKE VERITAS (DNV) = STRUCTURES = - Boat Design Net

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