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.1 – Page 8SECTION 1STRUCTURAL PRINCIPLESA. GeneralA 100 The scantling reduction101 The scantling reductions for high speed and light craft structures compared with Rules for Classificationof Ships are based on:—a certain stiffener spacing reduction ratio ---s s rs = chosen spacing in ms r = basic spacing = -------------------------- 2100 ( + L)m in general1000— longitudinal framing in bottom and strength deck— extended longitudinal and local buckling control— a sea and weather service restriction.A 200 Aluminium alloys201 The alloy grades are listed in Sec.2 Tables B1 to B4.202 The various formulae and expressions involving the factor f 1 may be applied when:σ ff 1 = --------240σ f = yield stress is not to be taken greater than 70% of the ultimate tensile strength.The material factor f 1 included in the various formulae and expressions is given in Sec.2 Tables B1 to B3 forthe un-welded condition and in Table B4 for the welded condition.B. Bottom StructuresB 100 Longitudinal stiffeners101 Single bottoms as well as double bottoms are normally to be longitudinally stiffened.102 The longitudinals should preferably be continuous through transverse members. If they are to be cut attransverse members, i.e. watertight bulkheads, continuous brackets connecting the ends of the longitudinals areto be fitted or welds are to be dimensioned accordingly.103 Longitudinal stiffeners are to be supported by bulkheads and web frames.104 Longitudinal stiffeners in slamming areas should have a shear connection to transverse members.B 200 Web frames201 Web frames are to be continuous around the cross section i.e. floors side webs and deck beams are to beconnected. Intermediate floors may be used.202 In the engine room plate floors are to be fitted at every frame. In way of thrust bearings additionalstrengthening is to be provided.B 300 Longitudinal girders301 Web plates of longitudinal girders are to be continuous in way of transverse bulkheads.302 A centre girder is normally to be fitted for docking purposes.303 Manholes or other openings should not be positioned at ends of girders without due consideration beingtaken of shear loadings.B 400 Engine girders401 Under the main engine, girders extending from the bottom to the top plate of the engine seating are to befitted.DET NORSKE VERITAS AS