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 11Fig. 1Wave coefficient202 The load point for which the design pressure shall be calculated is defined for various strength membersas follows:a) For plates: midpoint of horizontally stiffened plate.Half of the stiffener spacing above the lower support of vertically stiffened plate, or at lower edge of platewhen the thickness is changed within the plate.b) For stiffeners: midpoint of span.When the pressure varies other than linearly the design pressure shall be taken as the greater of:p m and p a + p---------------- b2p m’ p a and p b are calculated pressure at the midpoint and at each end respectively.c) For girders: midpoint of load area.B. AccelerationsB 100 General101 Accelerations in the craft’s vertical, transverse and longitudinal axes are in general obtained by assumingthe corresponding linear acceleration and relevant components of angular accelerations as statisticallyindependent variables. The combined acceleration in each direction may be taken as:n= number of independent variables.n2a c =a mm = 1Transverse or longitudinal component of the angular acceleration considered in the above expression shallinclude the component of gravity acting simultaneously in the same direction.102 The combined effects given in the following may deviate from the above general expression due topractical simplifications applicable to hull structural design or based on experience regarding phasing betweencertain basic components.DET 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 12B 200 Design vertical acceleration201 Design vertical acceleration at craft’s centre of gravity a cg shall be specified by the builder, and isnormally not to be less than:V 3.2a cg = ------- ------------fL L 0.76 g g 0 ( m ⁄ s 2 ).Minimum a cg =1 g 0 for service restriction R0-R4Minimum a cg =0.5 g 0 for service restriction R5-------Vneed not be taken greater than 3,0Lf g= acceleration factor (fraction of g 0 ) dependent of type and service notation and service area restrictionnotation given in Table B1.Table B1 Acceleration factor f gType and serviceService area restriction notationnotationR0 R1 R2 R3 R4 R5-R6Passenger 1) 1 1 1 1 0.5Car ferry 1) 1 1 1 1 0.5Cargo 4 3 2 1 1 0.5Patrol 7 5 3 1 1 0.5Yacht 1 1 1 1 1 0.51) Service area restriction R0 is not available for class notations Passenger and Car Ferry.The design vertical acceleration is an extreme value with a 1% probability of being exceeded, in the worstintended condition of operation.202 Unless otherwise established, the design acceleration at different positions along the craft’s length shallnot be less than:a v = k v a cgk v= longitudinal distribution factor taken from Fig.2.203 The allowable speed corresponding to the design vertical acceleration a cg , may be estimated from theformulas for the relationship between instantaneous values of a cg , V and H s , given in 204 and 205.204 When V ⁄ L ≥ 3:H sβ cg= significant wave height in m= deadrise angle at LCG in degrees= minimum 10°= maximum 30°B WL2 = water line breadth at L/2 in m.For twin- and multi hull vessels the total breadth of the hulls (exclusive tunnels) shall be usedg 0 = standard acceleration of gravity = 9.81 m/s 2k h = hull type factor given in Table B2.Table B2 Hull type factorHull typek hMonohull, Catamaran 1.0Wave Piercer 0.9SES, ACV 0.8Foil assisted hull (see 206) 0.7SWATH (see 206) 0.7k h g 0 Ha cg----------- S= -------------- + 0.084 ( 50 – β1650 B WL2 cg ) V------- 2 LB 2WL2------------------------ ( m ⁄ s 2 ) LΔDET NORSKE VERITAS AS
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RULES DET NORSKE VERITAS (DNV) = STRUCTURES = - Boat Design Net

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