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

Rules for High Speed, Light Craft and Naval Surface Craft, January 2011 Amended July 2011, see page 3Pt.3 Ch.3 Sec.6 – Page 30SECTION 6WEB FRAMES AND GIRDER SYSTEMSA. GeneralA 100 Introduction101 In this section the general requirements for simple girders and procedures for the calculations of complexgirder systems are given.A 200 Definitions201 Symbols:s = girder span in m. The web height of in-plane girders may be deductedb = breadth of load area in m (plate flange) b may be determined from Table A1p = design pressure in kN/m 2 according to Ch. 1 Sec.2P = design axial force in kNσ = nominal allowable bending stress in N/mm 2 due to lateral pressureτ = nominal allowable shear stress in N/mm 2σ c = critical buckling stress in N/mm 2σ el = ideal elastic buckling stress in N/mm 2Z = rule section modulus in cm 3A W = rule web area in cm 2A = rule cross-sectional area in cm 2t w = web thickness in mmh w = web height in mm= flange breadth in mm.b fA 300 Minimum thicknesses301 The thickness of structures are in general not to be less than:t 0 + kL st = ---------------- ---- ( mm)f s Rf =σ fss Rs-----s R= yield stress in N/mm 2 at 0.2% offset for unwelded alloy. σ f is not to be taken greater than 70% of theultimate tensile strength. For unwelded material, f may be taken as f 1 in Sec.2 Tables B1 to B3.= actual stiffener spacing in m= basic stiffener spacing in m=σ-------- f2402100 ( + L)--------------------------1000is not to be taken less than 0.5 or greater than 1.0.t 0 and k according to Table A2.Table A1 Breadth of load areaFor ordinary girders b = 0.5 (l 1 + l 2 (m)l 1 and l 2 are the spans in m of the supported stiffenersFor hatch side coamings b = 0.2 (B 1 - b 2 ) (m)B 1 = breadth of craft in m measured at the middle of the hatchwayb 2 = breadth of hatch in m measured at the middle of the hatchwayFor hatch end beams b = 0.4 b 3 (m)b 3 = distance in m between hatch end beam and nearest deep transverse girder or transversebulkheadDET NORSKE VERITAS AS