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

Amended July 2011, see page 3 Rules for High Speed, Light Craft and Naval Surface Craft, January 2011Pt.3 Ch.3 Sec.10 – Page 51102 For longitudinals and other stiffeners in the direction of compressive stresses, the critical buckling stresscalculated in 101 is to be related to the actual compressive stress as follows:σ cσ a≥ -----ησ aηη b= calculated extreme compressive stress, or ordinary local load stress divided by η G from D100= 0.85 for continuous stiffeners.=1– η b , maximum 0.85 for single-span stiffenerssimultaneous bending moment at midspan= ----------------------------------------------------------------------------------------------------bending moment capacityGuidance note:The resulting maximum allowable slenderness will be:100 l 830 K J – 0= ------------ī σ cσ c=σ----- aηK J-0 from Fig. 1.---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---E 200 Torsional buckling mode201 For longitudinals and other stiffeners in the direction of compressive stresses, the ideal elastic bucklingstress for the torsional mode may in general be calculated from formulae in Rules for Classification of ShipsPt.3 Ch.1 Sec.14.202 The critical buckling stress as found from 201 and A102 is not to be less than:σ aη= calculated extreme compressive stress, or ordinary local load stress divided by η G from D100= 0.85 in general= 0.8 when the adjacent plating is allowed to buckle in the elastic mode, according to G.Guidance note:To avoid torsional buckling the height of flats should not exceed:σ cσ a≥ -----ηt w = thickness of web in mmσ aσ c = -----ηK J - 0 from Fig.1.h wFor flanged profiles, 1 < ----- < 3:b fMinimum flange breadth may be taken as:For symmetrical flanges:140h w = t w----------------- (mm)σ------------ cK J – 0For unsymmetrical flanges:b f = 5lσ------------ c(mm)K J – 0DET NORSKE VERITAS AS