HULL STRUCTURAL DESIGN, ALUMINIUM ALLOY

Transcription

1 RULES FOR CLASSIFICATION OF HIGH SPEED, LIGHT CRAFT AND NAVAL SURFACE CRAFT STRUCTURES, EQUIPMENT PART 3 CHAPTER 3 HULL STRUCTURAL DESIGN, ALUMINIUM ALLOY JULY 2000 This booklet includes the relevant amendments and corrections shown in the January 2006 version of Pt.0 Ch.1 Sec.3. CONTENTS PAGE Sec. 1 Structural Principles... 5 Sec. 2 Materials and Material Protection... 9 Sec. 3 Manufacturing Sec. 4 Hull Girder Strength Sec. 5 Plating and Stiffeners Sec. 6 Web Frames and Girder Systems Sec. 7 Pillars and Pillar Bulkheads Sec. 8 Weld Connections Sec. 9 Direct Strength Calculations Sec. 10 Buckling Control Veritasveien 1, NO-1322 Høvik, Norway Tel.: Fax:

2 CHANGES IN THE RULES General The present edition of the rules includes additions and amendments decided by the Board as of June 2000, and supersedes the July 1996 edition of the same chapter. The rule changes come into force on 1 January This chapter is valid until superseded by a revised chapter. Supplements will not be issued except for an updated list of minor amendments and corrections presented in Pt.0 Ch.1 Sec.3. Pt.0 Ch.1 is normally revised in January and July each year. Revised chapters will be forwarded to all subscribers to the rules. Buyers of reprints are advised to check the updated list of rule chapters printed in Pt.0 Ch.1 Sec.1 to ensure that the chapter is current. Sec.2 Materials and Material Protection Item C200 containing requirements for documentation for information and approval is rewritten. Previous item C300 on survey and maintenance is moved to Pt.7 Ch.2 Previous items C400 to C600 are renumbered C300 to C500 and are expanded and completely rewritten. They now cover Coating, Cathodic protection and Other materials in contact with aluminium, respectively. Sec.8 Weld Connections In item B202, double continuous welds are now also required for all structures in tanks holding corrosive liquids. Main changes Sec.1 Structural Principles A new item H103 on coating is added. Corrections and Clarifications Besides the above stated rule changes, some corrections and clarifications have been made in the rule wording in compliance with current interpretations and the updating of other chapters of the rules. Comments to the rules may be sent by to rules@dnv.com For subscription orders or information about subscription terms, please use distribution@dnv.com Comprehensive information about DNV and the Society's services is found at the Web site Det Norske Veritas Computer Typesetting (FM+SGML) by Det Norske Veritas Printed in Norway If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas, then Det Norske Veritas shall pay compensation to such person for his proved direct loss or damage. However, the compensation shall not exceed an amount equal to ten times the fee charged for the service in question, provided that the maximum compensation shall never exceed USD 2 million. In this provision "Det Norske Veritas" shall mean the Foundation Det Norske Veritas as well as all its subsidiaries, directors, officers, employees, agents and any other acting on behalf of Det Norske Veritas.

3 Amended, Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 see Pt.0 Ch.1 Sec.3, January 2006 Pt.3 Ch.3 Contents Page 3 CONTENTS SEC. 1 STRUCTURAL PRINCIPLES... 5 A. General...5 A 100 The scantling reduction...5 A 200 Aluminium alloys...5 B. Bottom Structures...5 B 100 Longitudinal stiffeners...5 B 200 Web frames...5 B 300 Longitudinal girders...5 B 400 Engine girders...5 B 500 Double bottom, if fitted...5 C. Side Structure...5 C 100 Stiffeners...5 D. Deck Structure...5 D 100 Longitudinal stiffeners...5 D 200 Bulwarks...5 E. Flat Cross Structure...6 E 100 Definition...6 E 200 Longitudinal stiffeners...6 F. Bulkhead Structures...6 F 100 Transverse bulkheads...6 F 200 Corrugated bulkheads...6 G. Superstructures and Deckhouses...6 G 100 Definitions...6 G 200 Structural continuity...6 H. Structural Design in General...6 H 100 Craft arrangement...6 H 200 Soft local transitions...7 H 300 Impact strength...7 I. Some Common Local Design Rules...7 I 100 Definition of span...7 I 200 Effective girder flange...7 I 300 Sniped stiffeners...7 J. Support of Equipment and Outfitting Details...8 J 100 Heavy equipment, appendages etc...8 J 200 Minor outfitting details...8 K. Structural Aspects not Covered by Rules...8 K 100 Deflections...8 K 200 Local vibrations...8 SEC. 2 MATERIALS AND MATERIAL PROTECTION... 9 A. General...9 A 100 Application...9 A 200 Material certificates...9 B. Structural Aluminium Alloy...9 B 100 General...9 B 200 Aluminium grades...9 B 300 Chemical composition...9 B 400 Mechanical properties...9 C. Corrosion Protection...10 C 100 General...10 C 200 For information and approval...10 C 300 Coating...10 C 400 Cathodic protection...10 C 500 Other materials in contact with aluminium...11 D. Other Materials...11 D 100 Steel...11 D 200 Connections between steel and aluminium...11 D 300 Fibre Reinforced Plastic (FRP)...11 SEC. 3 MANUFACTURING A. General A 100 Basic requirements...12 B. Inspection B 100 General...12 B 200 Penetrant testing...12 B 300 Radiographic testing...12 B 400 Ultrasonic examination...12 C. Extent of Examination C 100 General...12 D. Acceptance Criteria for NDT D 100 Acceptance criteria...12 E. Testing E 100 Tanks...12 E 200 Closing appliances...12 SEC. 4 HULL GIRDER STRENGTH A. General A 100 Introduction...13 A 200 Definitions...13 B. Vertical Bending Strength B 100 Hull section modulus requirement...13 B 200 Effective section modulus...13 B 300 Hydrofoil on foils...13 B 400 Longitudinal structural continuity...13 B 500 Openings...14 C. Shear Strength C 100 Cases to be investigated...14 D. Cases to be Investigated D 100 Inertia induced loads...14 E. Transverse Strength of Twin Hull Craft E 100 Transverse strength...14 E 200 Allowable stresses...14 SEC. 5 PLATING AND STIFFENERS A. General A 100 Introduction...15 A 200 Definitions...15 A 300 Allowable stresses...15 B. Plating B 100 Minimum thicknesses...15 B 200 Bending...15 B 300 Slamming...15 C. Stiffeners C 100 Bending...16 C 200 Slamming...16 SEC. 6 WEB FRAMES AND GIRDER SYSTEMS A. General A 100 Introduction...18 A 200 Definitions...18 A 300 Minimum thicknesses...18 A 400 Allowable stresses...18 A 500 Continuity of strength members...18 B. Web Frames and Girders B 100 General...18 B 200 Effective flange...19 B 300 Effective web...19 B 400 Strength requirements...19 B 500 Girder tripping brackets...19 B 600 Girder web stiffeners...20

4 Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 Amended, Pt.3 Ch.3 Contents Page 4 see Pt.0 Ch.1 Sec.3, January 2006 SEC. 7 PILLARS AND PILLAR BULKHEADS A. General...21 A 100 Introduction...21 A 200 Definitions...21 B. Pillars...21 B 100 Arrangement of pillars...21 B 200 Cross-section particulars...21 B 300 Pillar scantlings...21 B 400 Pillars in tanks...22 C. Supporting Bulkheads...22 C 100 General...22 SEC. 8 WELD CONNECTIONS A. General...23 A 100 Introduction...23 A 200 Welding particulars...23 B. Types of Welded Joints...23 B 100 Butt joints...23 B 200 Tee or cross joints...23 C. Size of Connections...23 C 100 Fillet welds, general...23 C 200 Fillet welds and penetration welds subject to high tensile stresses...24 C 300 End connections of girders, pillars and cross ties...24 C 400 End connections of stiffeners...24 SEC. 9 DIRECT STRENGTH CALCULATIONS A. General...26 A 100 Introduction...26 A 200 Application...26 B. Plating...26 B 100 General...26 B 200 Calculation procedure...26 B 300 Allowable stresses...26 C. Stiffeners...26 C 100 General...26 C 200 Calculation procedure...26 C 300 Loads...26 C 400 Allowable stresses...26 D. Girders...26 D 100 General...26 D 200 Calculation methods...26 D 300 Design load conditions...27 D 400 Allowable stresses...27 SEC. 10 BUCKLING CONTROL A. General...28 A 100 Definitions...28 B. Longitudinal Buckling Load...28 B 100 Longitudinal stresses...28 C. Transverse Buckling Load...28 C 100 Transverse stresses...28 D. Plating...28 D 100 Plate panel in uni-axial compression...28 D 200 Plate panel in shear...29 D 300 Plate panel in bi-axial compression and shear...29 E. Stiffeners in Direction of Compression...30 E 100 Lateral buckling mode...30 E 200 Torsional buckling mode...30 E 300 Web and flange buckling...31 F. Stiffeners Perpendicular to Directionof Compression...31 F 100 Moment of inertia of stiffeners...31 G. Elastic Buckling of Stiffened Panels...31 G 100 Elastic buckling as a design basis...31 G 200 Allowable compression...32 H. Girders...32 H 100 Axial load buckling...32 H 200 Girders perpendicular to direction of compression...32 H 300 Buckling of effective flange...32 H 400 Shear buckling of web...32

5 Amended, Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 see Pt.0 Ch.1 Sec.3, January 2006 Pt.3 Ch.3 Sec.1 Page 5 SECTION 1 STRUCTURAL PRINCIPLES A. General A 100 The scantling reduction 101 The scantling reductions for high speed and light craft structures compared with Rules for Classification of Ships are based on: longitudinal framing in bottom and strength deck extended longitudinal and local buckling control a sea and weather service restriction. A 200 Aluminium alloys 201 The alloy grades are listed in Sec.2 Tables B1 to B The various formulae and expressions involving the factor f 1 may be applied when: f a certain stiffener spacing reduction ratio --- s s r s chosen spacing in m s r basic spacing ( L) m in general 1000 f 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 for the un-welded condition and in Table B4 for the welded condition. B. Bottom Structures B 100 Longitudinal stiffeners 101 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 at transverse members, i.e. watertight bulkheads, continuous brackets connecting the ends of the longitudinals are to 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 frames 201 Web frames are to be continuous around the cross section i.e. floors side webs and deck beams are to be connected. Intermediate floors may be used. 202 In the engine room plate floors are to be fitted at every frame. In way of thrust bearings additional strengthening is to be provided. B 300 Longitudinal girders 301 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 being taken of shear loadings. B 400 Engine girders 401 Under the main engine, girders extending from the bottom to the top plate of the engine seating are to be fitted. 402 Engine holdingdown bolts are to be arranged as near as practicable to floors and longitudinal girders. 403 In way of thrust bearing and below pillars additional strengthening is to be provided. B 500 Double bottom, if fitted 501 Manholes are to be cut in the inner bottom, floors and longitudinal girders to provide access to all parts of the double bottom. The vertical extension of lightening holes is not to exceed one half of the girder height. The edges of the manholes are to be smooth. Manholes in the inner bottom plating are to have reinforcement rings. Manholes are not to be cut in the floors or girders in way of pillars. 502 In double bottoms with transverse stiffening, longitudinal girders are to be stiffened at every transverse frame. 503 The longitudinal girders are to be satisfactorily stiffened against buckling. C. Side Structure C 100 Stiffeners 101 The craft's sides may be longitudinally or vertically stiffened. It is advised that longitudinal stiffeners are used near bottom and strength deck. 102 The continuity of the longitudinals is to be as required for bottom and deck longitudinals respectively. D. Deck Structure D 100 Longitudinal stiffeners 101 Decks are normally to be longitudinally stiffened. 102 The longitudinals should preferably be continuous through transverse members. If they are to be cut at transverse members, i.e. watertight bulkheads, continuous brackets connecting the ends of the longitudinals are to be fitted. 103 The plate thickness is to be such that the necessary transverse buckling strength is achieved, or transverse buckling stiffeners may have to be fitted intercostally. D 200 Bulwarks 201 The thickness of bulwark plates is not to be less than required for side plating in a superstructure in the same position. 202 A strong bulb section or similar is to be continuously welded to the upper edge of the bulwark. Bulwark stays are to be in line with transverse beams or local transverse stiffening. The stays are to have sufficient width at deck level. The deck beam is to be continuously welded to the deck in way of the

6 Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 Amended, Pt.3 Ch.3 Sec.1 Page 6 see Pt.0 Ch.1 Sec.3, January 2006 stay. Bulwarks on forecastle decks are to have stays fitted at every frame. Stays of increased strength are to be fitted at ends of bulwark openings. Openings in bulwarks should not be situated near the ends of superstructures. 203 Where bulwarks on exposed decks form wells, ample provision is to be made to freeing the decks for water. E. Flat Cross Structure E 100 Definition 101 Flat cross structure is horizontal structure above waterline like bridge connecting structure between twin hulls, etc. E 200 Longitudinal stiffeners 201 Flat cross structures are normally to be longitudinally stiffened. 202 The longitudinals should preferably be continuous through transverse members. If they are to be cut at transverse members, i.e. watertight bulkheads, continuous brackets connecting the ends of the longitudinals are to be fitted or welds are to be dimensioned accordingly. 203 Longitudinal stiffeners are to be supported by bulkheads and web frames. F. Bulkhead Structures F 100 Transverse bulkheads 101 Number and location of transverse watertight bulkheads are to be in accordance with the requirements given in Ch.1 Sec.1 B The stiffening of the upper part of a plane transverse bulkhead is to be such that the necessary transverse buckling strength is achieved. F 200 Corrugated bulkheads 201 Longitudinal and transverse bulkheads may be corrugated. 202 For corrugated bulkheads the following definition of spacing applies (see Fig. 1): s s 1 for section modulus calculations 1,05 s 2 or 1,05 s 3 for plate thickness calculations. freeboard deck, extending from side to side of the ship or with the side plating not inboard of the shell plating more than 4% of the breadth (B). 102 Deckhouse is defined as a decked structure above the strength deck with the side plating being inboard of the shell plating more than 4% of the breadth (B). Long deckhouse - deckhouse having more than 0,2 L of its length within 0,4 L amidships. Short deckhouse - deckhouse not defined as a long deckhouse. G 200 Structural continuity 201 In superstructures and deckhouses, the front bulkhead is to be in line with a transverse bulkhead in the hull below or be supported by a combination of girders and pillars. The after end bulkhead is also to be effectively supported. As far as practicable, exposed sides and internal longitudinal and transverse bulkheads are to be located above girders and frames in the hull structure and are to be in line in the various tiers of accommodation. Where such structural arrangement in line is not possible, there is to be other effective support. 202 Sufficient transverse strength is to be provided by means of transverse bulkheads or girder structures. 203 At the break of superstructures, which have no set-in from the ship's side, the side plating is to extend beyond the ends of the superstructure, and is to be gradually reduced in height down to the deck or bulwark. The transition is to be smooth and without local discontinuities. A substantial stiffener is to be fitted at the upper edge of plating. The plating is also to be additionally stiffened. 204 In long deckhouses, openings in the sides are to have well rounded corners. Horizontal stiffeners are to be fitted at the upper and lower edge of large openings for windows. Openings for doors in the sides are to be substantially stiffened along the edges. The connection area between deckhouse corners and deck plating is to be increased locally. Deck girders are to be fitted below long deckhouses in line with deckhouse sides. 205 Deck beams under front and aft ends of deckhouses are not to be scalloped for a distance of 0,5 m from each side of the deckhouse corners. 206 For deckhouse side stiffeners the scantlings need not be greater than required for tween deck frames with equivalent end connections. 207 Casings supporting one or more decks above are to be adequately strengthened. Fig. 1 Corrugated bulkhead G. Superstructures and Deckhouses G 100 Definitions 101 Superstructure is defined as a decked structure on the H. Structural Design in General H 100 Craft arrangement 101 Attention is drawn to the importance of structural continuity in general. 102 The craft arrangement is to take into account: continuity of longitudinal strength, including horizontal shear area to carry a strength deck along transverse bulkheads or strongwebs web or pillar rings in engine room twin hull connections access for inspection superstructures and deckhouses: direct support transitions deck equipment support multi-deck pillars in line, as practicable

7 Amended, Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 see Pt.0 Ch.1 Sec.3, January 2006 Pt.3 Ch.3 Sec.1 Page 7 external attachments, inboard connections. 103 Structural details in spaces that will be coated are to be designed in such way that a sound layer of coating can be achieved everywhere. H 200 Soft local transitions 201 Gradual taper or soft transition is specially important in high speed aluminium vessels, to avoid: stress corrosion and fatigue in heavy stressed members impact fatigue in impact loaded members. 202 End brackets, tripping brackets etc. are not to terminate on unsupported plating. Brackets are to extend to the nearest stiffener, or local plating reinforcement is to be provided at the toe of the bracket. H 300 Impact strength 301 The slamming pressure in Ch.1 is (contrary to the Rules for Classification of Ships) expressed as an equivalent static load, and is to be compared with ordinary allowable stresses. I. Some Common Local Design Rules I 100 Definition of span 101 The effective span of a stiffener (l) or girder (S) depends on the design of the end connections in relation to adjacent structures. Unless otherwise stated the span points at each end of the member, between which the span is measured, is to be determined as shown on Fig.1. It is assumed that brackets are effectively supported by the adjacent structure. For stiffeners, see also Fig. 2 or Sec.5. l R S effective area of the flange is given by: A e k t f b f (mm 2 ) b f total face plate breadth in mm k flange efficiency coefficient, see also Fig. 3 rt k f b 1,0 maximum k 1 b s t f t w r β 0643, ( sinhβcoshβ + sinβcosβ) sinh 2 β + sin 2 β for symmetrical and unsymmetrical free flange , ( sinhβ + sinβ) ( coshβ cosβ) sinh 2 β + sin 2 β for girder flange with two webs 156, ( coshβ cosβ) sinhβ + sinβ for box girder flange with multiple webs , 285b (rad) rt f 0,5 (b f t w ) for symmetrical free flanges b f for unsymmetrical free flanges s t w for box girder flanges spacing of supporting webs for box girder (nun) face plate thickness in general (mm) t w (maximum) for unsymmetrical free flanges web plate thickness (mm) radius of curved face plate (mm) b 2 3 b 2 3 R l S l b 2 3 b Fig. 3 Effective width of curved face plates for alternative boundary conditions Fig. 2 Span points STIFFENERS GIRDERS I 200 Effective girder flange 201 For girders with curved face plate, e.g. web frames, the 202 The effective width of curved plate flanges, or effective width of plate at knuckles, is to be specially considered. I 300 Sniped stiffeners 301 Stiffeners with sniped ends may be allowed where dynamic loads are small and vibrations considered to be of small importance.

8 Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 Amended, Pt.3 Ch.3 Sec.1 Page 8 see Pt.0 Ch.1 Sec.3, January 2006 J. Support of Equipment and Outfitting Details J 100 Heavy equipment, appendages etc. 101 Whether the unit to be supported is covered by classification or not, the forces and moments at points of attachment have to be estimated and followed through hull reinforcements in line, through craft girder and pillar system (taking into account hull stresses already existing) until forces are safely carried to craft's side or bulkheads. 102 Doublers should be avoided normal to a tensile force. J 200 Minor outfitting details 201 Generally connections of outfitting details to the hull are to be such that stress-concentrations are minimized and welding to high stressed parts are avoided wherever possible. Connections are to be designed with smooth transitions and proper alignment with the hull structure elements. Terminations are to be supported. 202 Connections to topflange of girders and stiffeners are to be avoided if not well smoothened. Preferably supporting of outfittings are to be welded to the stiffener web. K. Structural Aspects not Covered by Rules K 100 Deflections 101 Requirements for minimum moment of inertia or maximum deflection under load are limited to structure in way of hatches and doors and some other special cases. 102 Deflection problems in general are left to designer's consideration. K 200 Local vibrations 201 The evaluation of structural response to vibrations caused by impulses from engine and propeller blades and jet units are not covered by the classification, but the builder is to provide relevant documentation. HSC Code 3.4: Cyclic loads, including those from vibrations which can occur on the craft should not: a) impair the integrity of structure during the anticipated service life of the craft or the service life agreed with the Administration; b) hinder normal functioning of machinery and equipment; and c) impair the ability of the crew to carry out its duties. Upon request such evaluation may be undertaken by the Society.

9 Amended, Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 see Pt.0 Ch.1 Sec.3, January 2006 Pt.3 Ch.3 Sec.2 Page 9 SECTION 2 MATERIALS AND MATERIAL PROTECTION A. General A 100 Application 101 The rules in this chapter apply to wrought aluminium alloys for objects classified or intended for classification with the Society. A 200 Material certificates 201 Rolled and extruded wrought aluminium alloys, glass reinforced plastic and core materials for hull structures and rolled steel are normally to be supplied with DNV material certificates. 202 For class certificate requirement for chemical composition, mechanical properties, heat treatment and repair of defects, see Pt.2 Ch Particular attention is to be given to aluminium hull materials specification in Pt.2 Ch Requirements for material certificates for forgings, castings and other materials for special parts and equipment are stated in connection with the rule requirements for each individual part. B. Structural Aluminium Alloy B 100 General 101 Aluminium alloy for marine use may be applied in hulls, superstructures, deckhouses, hatch covers and sundry items. B 200 Aluminium grades 201 Aluminium alloys are to have a satisfactory resistance to corrosion in marine environments. Grades for welded structures are to be weldable, applying one of the welding methods approved by the Society. 202 For major hull structural components, alloys with temper H116/H321 for rolled products, and alloys with temper T5/ T6 for extruded products, are normally to be used. The use of 0- or F temper must be agreed with the Society. 203 The use of 6000 series aluminium alloys in direct contact with sea water may be restricted depending on application and corrosion protection system. The use of these alloys are to be agreed with the Society. 204 In weld zones (HAZ) of rolled or extruded products, the factor f 1 given in Table B4 may in general be used as basis for the scantling requirements. 205 Welding consumables are to be chosen according to Table C2 in Pt.2 Ch.3 Sec.2. The consumable chosen are to have minimum mechanical properties not less than specified for the parent alloy in the welded condition. B 300 Chemical composition 301 The chemical composition is to satisfy the requirements in Pt.2 Ch.2. Other alloys or alloys which do not fully comply with Pt.2 Ch.2, may be accepted by the Society after consideration in each particular case. Special tests and/or other relevant information, e.g. which confirm a satisfactory corrosion resistance and weldability, may be required. B 400 Mechanical properties 401 Requirements to mechanical properties for different delivery conditions are given in Tables B1 and B2 for wrought products, extruded products and rivet bars/-rivets, respectively. Other delivery conditions with related mechanical properties may be accepted by the Society after consideration in each particular case. Table B1 Factor f 1 for wrought aluminium alloy sheets, strips and plates, t: 2 mm t 40 mm DNV Designation Temper f 1 NV-5052 H32 H NV-5154A 0, H NV-5754 H NV-5454 H32 H V-5086 H116, H32 H NV-5083 H116, H NV-5383 H116, H Note: For tempers 0 and H111, the factor f 1 is to be taken from Table B4. Table B2 Factor f 1 for extruded aluminium alloy profiles, rods and tubes, t: 2 mm t 25 mm DNV Designation Temper f 1 NV-6060 T NV-6061 T4 T5/T NV-6063 T5 T NV-6005A T5/T NV-6082 T4 T5/T Note: Table B2 only applies when the main loading direction is logitudinal to the extrusion, see also Table B3. Table B3 Factor f 1 for extruded aluminium alloy profiles, rods and tubes, t: 2 mm t 25 mm, transverse to extruding direction DNV Designation Temper f 1 NV-6060 T NV-6061 T4 T5/T NV-6005A T5/T6 6 < t < < t < NV-6082 T5 / T Note: Table B2 only applies when the main loading direction is logitudinal to the extrusion Table B4 Factor f 1 in the welded condition DNV Designation Temper Filler f 1 NV , H111, H32, H NV-5154A 0, H NV , H111, H NV , H111, H32, H NV , H111, H116, H32, H34 NV-5083 H116, H321 H116, H ) )

10 Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 Amended, Pt.3 Ch.3 Sec.2 Page 10 see Pt.0 Ch.1 Sec.3, January 2006 Table B4 Factor f 1 in the welded condition (Continued) DNV Designation Temper Filler f 1 NV-5383 H116, H ) NV-6060 T NV-6061 T4 T5/T NV-6063 T T6 NV-6005A T5/T NV-6082 T4 T5/T ) The utilisation of the material is higher than given by the f 1 factor as given in Sec. 1 A. This is due to extended utilisation in Rules for HS, LC and NSC, f 1 ( 1 /240) x ) The utilisation of the material is higher than given by the f 1 factor as given in Sec. 1 A. This is due to extended utilisation in Rules for HS, LC and NSC, f 1 ( 1 /240) x 1.10 C. Corrosion Protection C 100 General 101 Loss of structural strength due to corrosion is not acceptable. 102 All surfaces that are not recognised as inherently resistant to the actual marine environment are to be adequately protected against corrosion. In these rules, corrosion is defined as degradation of material due to environmental influence. C 200 For information and approval 201 Specifications for corrosion protection, i.e. for coating, if applied, see 301, and for cathodic protection (including calculations), see 403, are to be submitted for information. The specifications are basis for approval of drawings of the cathodic protection system. 202 Drawings of cathodic protection system, e.g. fastening, numbers and distribution of anodes and reference electrodes (if impressed current), are subject to approval. 203 Selection and combination of materials for exposure to sea water and/or marine atmosphere are subject to approval. C 300 Coating 301 If coating is applied, the specification is to be submitted for information. Coating of aluminium hulls is normally not required (see B200). However, hulls normally need to be coated for anti-fouling purposes. When coating is applied, it will influence the corrosion resistance of the hull, and constitute a basis for cathodic protection design. The coating system including surface preparation before coating should therefore be submitted for information. The following is normally included in a specification for coating: metal surface cleaning and preparation before application of the primer coat, including treatment of edges and welds build-up and application of coating system with individual coats curing times and over-coating intervals acceptable temperatures of air and metal surface and dryness or humidity conditions during the above mentioned operations (normally, the metal surface is minimum 3 C above the dew point and the relative humidity is below 85 %) thickness of individual coats and final coating system resistance to cathodic disbonding (for coatings to be used in connection with impressed current). 302 A sound anti-corrosion coating should always be combined with the anti-fouling coating on the external hull. 303 Anti-corrosion coating is not to contain copper or other constituents that may cause galvanic corrosion on the aluminium hull. 304 Hull integrated water ballast tanks and other tanks holding corrosive liquids are to be coated. All stiffeners and frames in these tanks are to be welded to plating with double continuous welding, see Sec.8 B In other internal compartments of the hull where corrosive water is likely to occur, the lower 0.5 m of the internal bottom surface, measured along the plate on each side of the keel, and the corresponding section of the bulkheads, is normally to be coated. The preparation of surfaces including welds and edges shall be such that the coating can be properly applied. The use of 6000 alloys containing more than 0,15% Cu in internal compartments without coating may be restricted. Stagnant, chloride-containing water in internal compartments, e.g. condensation water, may cause corrosion on aluminium alloy plates and structures. Corrosion attacks will usually be of localised type, e.g. in the form of pitting. Corrosion attacks of galvanic type may also occur, see also 500, e.g. if equipment made of other metal alloy remains in electrical contact with aluminium alloy material. Corrosion attacks of the above mentioned types can be reduced by means of e.g.: coating applied as described above regular cleaning, drying and inspection of the actual compartment electrical isolation of any other metallic part from aluminium alloy plates and structures use of dehumidifying equipment in a closed compartment ventilation holes (minimum 2) drainage holes hot air fans. C 400 Cathodic protection 401 Cathodic protection of aluminium hulls can be obtained with aluminium or zinc sacrificial anodes or impressed current. Magnesium based sacrificial anodes are not to be used, and impressed current is not to be used in internal hull compartments. 402 Cathodic protection is normally to be applied to aluminium hull craft due to electrical connection of the aluminium with another metals (in propeller, water jet, etc.), which may initiate galvanic corrosion, and to protect the hull against local corrosion and damage that normally will occur in protective coatings. 403 The following is normally to be included in a cathodic protection specification: areas to be protected (m 2 ) for hull and attached metallic components such as water jet unit and water jet duct stipulated protective current density demand (ma/m 2 ) for coated and not coated surfaces of hull and attached components, respectively total current demand (A) target design life of cathodic protection system anode material and manufacturer for sacrificial anodes; calculation of anode mass, distribution, total number for impressed current systems; current capacity of rectifiers and anodes

11 Amended, Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 see Pt.0 Ch.1 Sec.3, January 2006 Pt.3 Ch.3 Sec.2 Page 11 for impressed current systems; reference electrodes, system control and monitoring arrangement, cabling and procedures for exchange or renewal of components target protective potential difference to be obtained drawings of cathodic protection systems, showing anode types, mass, distribution, location and attachment details (for sacrificial anodes or impressed current anodes with reference electrodes) cathodic protection system drawings shall be in compliance with the specification and calculations for the same. The current density demand will vary dependent upon the speed of hull, the speed of propeller, and the type of metallic material to be protected (aluminium, stainless steel, etc.). The target protective potential difference for aluminium alloy surfaces may be minus 950 mv versus the Ag/AgCl/seawater reference electrode, with an acceptable potential difference range of minus 800 mv to minus 1150 mv, i.e. approximately as for carbon steel and stainless steel. Due concern must be given to the possibility of detrimental overprotection of aluminium. Stainless steel surfaces in water jet units of high speed craft may need a current density of up to about 300 ma/m 2 to be protected, while values as high as 500 ma/m 2 may give overprotection problems. 404 For documentation of instrumentation and automation, including computer based control and monitoring, see Pt.4 Ch.9 Sec The designed (target) service life of a cathodic protection system is normally to be at least as long as the expected time interval between dockings. 406 With impressed current cathodic protection systems, precautions are to be taken to avoid: 1) overprotection or excessive negative potential differences locally, especially on aluminium surfaces (implying transpassive corrosion) as well as 2) loss of protection, by means of anode screens, automatic voltage control, overprotection alarm, or similar. The protective potential difference is to be kept within a specified and agreed range, see Guidance note to Direct voltage stray currents may impose rapid electrolytic corrosion damage to hulls and is to be avoided. Stray D.C. sources may be shore connections (e.g. ramps, cranes, cables, etc.), not properly grounded welding machines, etc. Special precautions should be taken if welding is carried out with the craft afloat, or if the craft is connected to electrical power in port. C 500 Other materials in contact with aluminium 501 If other metallic materials are used in propellers or impellers, piping, pumps, valves, etc. and are in contact with the aluminium hull, provisions are to be made to avoid galvanic corrosion. Acceptable provisions are either one of or a combination of: coating of water or moisture exposed surfaces electrical isolation of different materials from each other cathodic protection. Full electrical isolation of e.g. propeller or impeller from hull is usually difficult. Contact will be established when the propeller is idle. Wooden material, cloth, debris, non-adherent coating or other organic material remaining in durable contact with aluminium may cause under-deposit corrosion on aluminium due to local oxygen deficiency at the surface. D. Other Materials D 100 Steel 101 Structural steel may be used in sundry items such as rudders, foils, propeller shaft brackets, etc. 102 For requirements for chemical composition, mechanical properties, heat treatment, testing and repair of defects, see Pt The material factor f 1 1 for ordinary ship quality steel. 104 All steel surfaces are to be protected against corrosion by paint of suitable composition or other effective coating. 105 Shop primers applied over areas which will subsequently be welded, are to be of a quality accepted by the Society as having no detrimental effect on the finished weld. See Register of Approved Manufacturers and Register of Type Approved Products. 106 Coating systems are to be suitable for use on any previously applied shop primer. The coating and the assumed application conditions must have been approved by the Society. Such approval will normally be given as a «Type approval». The shipbuilders are to present a written declaration stating that the coating has been applied as specified. Upon request approval programs for coating systems may be obtained from the Society. D 200 Connections between steel and aluminium 201 If there is risk of galvanic corrosion, provisions are to be made, see C Aluminium plating connected to a steel boundary bar is wherever possible to be arranged on the side exposed to moisture. 203 Direct contact between exposed wooden materials, e.g. deck planking, and aluminium is to be avoided. 204 Bolts with nuts and washers are either to be of stainless steel or hot galvanized steel. The bolts are in general to be fitted with sleeves of insulating material. D 300 Fibre Reinforced Plastic (FRP) 301 FRP materials, core materials and fillers are to be approved according to Sec Other reinforcement and plastic materials may be approved on the basis of relevant documentation and testing in each individual case.

12 Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 Amended, Pt.3 Ch.3 Sec.3 Page 12 see Pt.0 Ch.1 Sec.3, January 2006 SECTION 3 MANUFACTURING A. General A 100 Basic requirements 101 Welding of hull structures, machinery installations and equipment are to be carried out by approved welders, with approved welding consumables and at welding shops recognised by the Society. See Sec Shot blasting, priming and coating are to be carried out under indoor conditions. For coating specification and documentation, see Sec For vessels longer than 50 m, a plan for non-destructive testing (NDT) is to be submitted for approval. B. Inspection B 100 General 101 Welds are to be subject to visual survey and inspection as fabrication proceed. NDT is to be performed according to established procedures and if required, qualified for the work. 102 All examinations are to be carried out by competent personnel. The NDT operators are to be qualified according to a recognised certification scheme accepted by the Society. The certificate is clearly to state the qualifications as to which examination method and within which category the operator is qualified. B 200 Penetrant testing 201 Penetrant testing is to be carried out as specified in the approved procedures. B 300 Radiographic testing 301 Radiographic testing is to be carried out as specified in the approved procedures. 302 Processing and storage are to be such that the films maintain their quality throughout the agreed storage time. The radiographs are to be free from imperfections due to development processing. B 400 Ultrasonic examination 401 Ultrasonic testing is to be carried out as specified in the approved procedures. Ultrasonic examination procedures are to contain sketches for each type of joint and dimensional range of joints which clearly show scanning pattern and probes to be used. 402 The examination record is to include the imperfection position, the echo height, the dimensions (length), the depth below the surface and, if possible, the defect type. C. Extent of Examination C 100 General 101 All welds are to be subject to visual examination. In addition to the visual examination, at least 2 to 5 % of total welded length are to be examined by penetrant examination and/or radiographic examination. For highly stressed areas the extent of examination may be increased. 102 If defects are detected, the extent of examination is to be increased to the surveyor s satisfaction. D. Acceptance Criteria for NDT D 100 Acceptance criteria 101 All welds are to show evidence of good workmanship. The quality is normally to comply with ISO quality level C, intermediate. For highly stressed areas more stringent requirements, such as ISO level B, may be applied. E. Testing E 100 Tanks 101 Protective coating systems may be applied before water testing. All pipe connections to tanks are to be fitted before testing. If engine bed plates are bolted directly on the inner bottom plating, the testing of the double bottom tank is to be carried out with the engine installed. 102 Unless otherwise agreed, all tanks are to be tested with a water head equal to the maximum pressure to which the compartment may be exposed. The water is in no case to be less than to the top of the air pipe or to a level h 0 above the top of the tank except where partial filling alone is prescribed. h 0 0,03 L - 0,5 (m), minimum 1, generally pressure valve opening pressure when exceeding the general value. E 200 Closing appliances 201 Inner and outer doors below the waterline are to be hydraulically tested. 202 Weathertight and watertight closing appliances not subjected to pressure testing are to be hose tested. The nozzle inside diameter is to be 12,5 mm and the pressure at least 250 kn/ m 2. The nozzle should be held at a distance of maximum 1,5 m from the item during the test. Alternative methods of tightness testing may be considered. 203 All weathertight or watertight doors and hatches are to be function tested.

13 Amended, Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 see Pt.0 Ch.1 Sec.3, January 2006 Pt.3 Ch.3 Sec.4 Page 13 SECTION 4 HULL GIRDER STRENGTH A. General A 100 Introduction 101 In this section requirements for longitudinal and transverse hull girder strength is given. In addition, buckling control according to Sec. 10 may be required. 102 Longitudinal strength has generally to be checked for the craft types and sizes mentioned in the introduction to Ch.1 Sec For new designs (prototypes) of large and structurally complicated craft (e.g. multi-hull types) a complete 3-dimensional global analysis of the transverse strength, in combination with longitudinal stresses, is to be carried out. 104 Buckling strength in bottom and deck may, however, have to be checked also for the other craft. A 200 Definitions 201 Moulded deck line, Rounded sheer strake, Sheer strake and Stringer plate are as defined in Fig.1. B 200 Effective section modulus 201 Where calculating the moment of inertia and section modulus of the midship section, the effective sectional area of continuous longitudinal strength members is in general the net area after deduction of openings. Superstructures which do not form a strength deck are not to be included in the net section. This applies also to deckhouses and bulwarks. 202 The effect of openings are assumed to have longitudinal extensions as shown by the shaded areas in Fig.2, i.e. inside tangents at an angle of 30 to each other. Example for transverse section III: b III b' + b + b 203 For twin hull vessels the effective breadth of wide decks without longitudinal bulkhead support will be considered separately. B 300 Hydrofoil on foils 301 For hydrofoils in addition to the calculation for the midship section, the sections in way of the foils are required to be checked. B 400 Longitudinal structural continuity 401 The scantling distribution of structures participating in the hull girder strength in the various zones of the hull is to be carefully worked out so as to avoid structural discontinuities resulting in abrupt variations of stresses. 402 At ends of effective continuous longitudinal strength members in deck and bottom region large transition brackets are to be fitted. Fig. 1 Deck corners B. Vertical Bending Strength B Hull section modulus requirement M Z ( cm 3 ) M the longitudinal midship bending moment in knm from Ch.1 Sec. 3 sagging or hogging bending moment hollow landing or crest landing bending moment maximum still water + wave bending moment for high speed displacement craft and semi-planing craft in the displacement mode maximum total moment for hydrofoil on foils 175 f 1 N/mm 2 in general. Simultaneous end impacts over a hollow are considered less frequent and giving lower moments than the crest landing. Need not be investigated if deck buckling resistance force is comparable to that of the bottom. Fig. 2 Effect of openings

14 Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 Amended, Pt.3 Ch.3 Sec.4 Page 14 see Pt.0 Ch.1 Sec.3, January 2006 B 500 Openings 501 A keel plate for docking is normally not to have openings. In the bilge plate, within 0,5 L amidships, openings are to be avoided wherever practicable. Any necessary openings in the bilge plate are to be kept clear of a bilge keel. 502 Openings in strength deck are wherever practicable to be located well clear of the craft s side and hatch corners. 503 Openings in strength members should generally have an elliptical form. Larger openings in deck may be accepted with well rounded corners and are to be situated as near to the craft's centreline as practicable. 504 For corners with rounded shape the radius is not to be less than: r 0,025 B dk (m) B dk breadth of strength deck. r need not be taken greater than 0,1 b (m) where b breadth of opening in m. For local reinforcement of deck plating at circular corners, see Sec. 5 B. 505 Edges of openings are to be smooth. Machine flame cut openings with smooth edges may be accepted. Small holes are to be drilled. 506 Studs for securing small hatch covers are to be fastened to the top of a coaming or a ring of suitable thickness welded to the deck. The studs are not to penetrate the deck plating. C. Shear Strength C 100 Cases to be investigated 101 If doors are arranged in the craft's side, the required sectional area of the remaining side plating will be specially considered. 102 If rows of windows are arranged below strength deck, sufficient horizontal shear area must be arranged to carry down the midship tension and compression. 103 In these and other locations with doubtful shear areas, allowable shear stress may be taken as: allowable bending stress τ D. Cases to be Investigated D 100 Inertia induced loads 101 Transversely framed parts of forebody are to be checked for the axial inertia force given in Ch.1 Sec.3 A700: F L a l (kn) a l maximum surge acceleration, not to be taken less than: V 0,4 g for L 0,2 g for V L The distribution of stresses will depend on instantaneous forward immersion and on location of cargo. 102 Bottom structure in way of thrust bearings may need a check for the increased thrust when vessel is retarded by a crest in front. 103 Allowable axial stress and associated shear stresses will be related to the stresses already existing in the region. 104 For passenger craft, a separate analysis is to be performed to investigate the structural consequence when subject to the collision load as given in the International Code of Safety for High-Speed Craft, paragraph (see Ch.7 Sec.1 B300). Inertia forces from the collision deceleration should be considered for shear and buckling in the foreship area, and for the forces acting on the supporting structure for cargo. E. Transverse Strength of Twin Hull Craft E 100 Transverse strength 101 The twin hull connecting structure is to have adequate transverse strength related to the design loads and moments given in Ch When calculating the moment of inertia, and section modulus of the longitudinal section of the connecting structure, the effective sectional area of transverse strength members is in general to be taken as the net area with effective flange after deduction of openings. The effective shear area of transverse strength members is in general to be taken as the net web area after deduction of openings. E 200 Allowable stresses 201 The equivalent stress is defined as: x y τ V linear interpolaton of a l for 3 < < 5 l total normal stress in x-direction total normal stress in y-direction total shear stress in the xy-plane. By total stress is meant the arithmetic sum of stresses from hull girder and local forces and moments. 202 The following total stresses are normally acceptable: normal stress: 160 f 1 (N/mm 2 ) mean shear stress: τ 90 f 1 (N/mm 2 ) equivalent stress: e 180 f 1 (N/mm 2 ). c 2 x + 2 y x y + 3τ 2

15 Amended, Rules for High Speed, Light Craft and Naval Surface Craft, July 2000 see Pt.0 Ch.1 Sec.3, January 2006 Pt.3 Ch.3 Sec.5 Page 15 SECTION 5 PLATING AND STIFFENERS A. General A 100 Introduction 101 In this section the general requirements for plate thicknesses and local strength of panels of aluminium alloy are given. 102 Buckling strength requirements are related to longitudinal hull girder stresses. Panels subjected to other compressive, shear or biaxial stresses will be specially considered. Table A1 Allowable bending stresses Item Plate Stiffener (N/mm 2 ) Bottom, slamming load 200 f f 1 Bottom, sea load 180 f f 1 Side 180 f f 1 Deck 180 f f 1 Flat cross structure, slamming load 200 f f 1 Flat cross structure, sea load 180 f f 1 Bulkhead, collision 180 f f 1 Superstructure/deckhouse front 160 f f 1 Superstructure/deckhouse side/ deck 180 f f 1 Bulkhead, watertight 220 f f 1 Tank bulkhead 180 f f 1 A 200 Definitions 201 Symbols: t rule thickness of plating in mm Z rule section modulus of stiffener in cm 3 s stiffener spacing in m, measured along the plating l stiffener span in m, measured along the top flange of the member. The depth of stiffener on crossing panel may be deducted when deciding the span. For curved stiffeners l may be taken as the chord length p design pressure in kn/m 2 as given in Ch.1 Sec.2 nominal allowable bending stress in N/mm 2 due to lateral pressure (see Table A1) f 1 see Sec.l A202 τ nominal allowable shear stress in N/mm 2. A 300 Allowable stresses 301 Maximum allowable bending stresses in plates and stiffeners are to be according to Table A1. B. Plating B 100 Minimum thicknesses 101 The thickness of structures is in general not to be less than: f f 240 t t 0 + kl f s ---- (mm) s R f s s R s ---- is not to be taken less than 0.5 or greater than 1.0. s R t 0 and k according to Table B1. B 200 Bending 201 The general requirement for thickness of plating subject to lateral pressure is given by: C yield stress in N/mm 2 at 0.2% offset for unwelded alloy. f is not to be taken greater than 70 % of the ultimate tensile strength actual stiffener spacing (m) basic stiffener spacing (m) Table B1 Values of t 0 and k Item t 0 k Bottom, bilge and side to loaded water line Shell plating Side above loaded water line Bottom aft in way of rudder, shaft brackets etc. Strength deck weather part forward of amidships Strength deck weather part aft of amidships Deck and Inner bottom inner bottom plating Car deck Accommodation deck Deck for cargo Superstructure and deckhouse decks Bulkhead plating Other structures 2100 ( + L) Collision bulkhead Tank bulkhead Other watertight bulkheads Superstructure and deckhouse front Superstructure and deckhouse sides and aft Foundations Structures not mentioned above t s Cp (mm) correction factor for aspect ratio ( s/l) of plate field and degree of fixation of plate edges given in Table B The thickness requirement for a plate field clamped along all edges and with an aspect ratio 0.5: 22.4s p t (mm). B 300 Slamming 301 The bottom plating is to be strengthened according to the requirements given in 302 to 303.