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RULES FOR CLASSIFICATION. Ships. Part 3 Hull Chapter 5 Hull girder strength. Edition January 2017 DNV GL AS - PDF
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1 RULES FOR CLASSIFICATION Ships Edition January 2017 Part 3 Hull Chapter 5 The content of this service document is the subject of intellectual property rights reserved by ("DNV GL"). The user accepts that it is prohibited by anyone else but DNV GL and/or its licensees to offer and/or perform classification, certification and/or verification services, including the issuance of certificates and/or declarations of conformity, wholly or partly, on the basis of and/or pursuant to this document whether free of charge or chargeable, without DNV GL's prior written consent. DNV GL is not responsible for the consequences arising from any use of this document by others. The electronic pdf version of this document, available free of charge from is the officially binding version.
2 FOREWORD DNV GL rules for classification contain procedural and technical requirements related to obtaining and retaining a class certificate. The rules represent all requirements adopted by the Society as basis for classification. January 2017 Any comments may be sent by to If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of DNV GL, then DNV GL 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 "DNV GL" shall mean, its direct and indirect owners as well as all its affiliates, subsidiaries, directors, officers, employees, agents and any other acting on behalf of DNV GL.
3 CHANGES CURRENT This document supersedes the July 2016 edition. Changes in this document are highlighted in red colour. However, if the changes involve a whole chapter, section or sub-section, normally only the title will be in red colour. Main changes January 2017, entering into force as from date of publication Sec.2 Vertical hull girder bending and shear strength Sec.2 [2.3.1]: Error correction. Sec.3 Hull girder yield check Sec.3 [3.1.1]: A new factor C ht is introduced in connection with modified horizontal wave bending moment in Ch.4. Editorial corrections In addition to the above stated changes, editorial corrections may have been made. Part 3 Chapter 5 Changes - current Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 3
4 CONTENTS Changes current... 3 Section 1 Strength characteristics of hull girder transverse sections General Scope Hull girder transverse sections General Structural members not contributing to hull girder sectional area Continuous trunks and longitudinal continuous hatch coamings Longitudinal stiffeners or girders welded above the strength deck Longitudinal bulkheads with corrugations Members in materials other than steel Definitions of openings Large openings Isolated small openings Lightening holes, draining holes and single scallops Non-continuous decks and longitudinal bulkheads Longitudinal members with reduced effectiveness... 9 Part 3 Chapter 5 Contents Section 2 Vertical hull girder bending and shear strength Vertical hull girder bending strength General Definition of hull girder section modulus Minimum section modulus at midship part Section modulus Minimum moment of inertia at midship part Extent of high tensile steel Permissible still water bending moments for harbour/sheltered water operations Vertical hull girder shear strength Total hull girder shear capacity Seagoing condition Harbour/sheltered water operations Shear force correction Section 3 Hull girder yield check General Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 4
5 1.1 Scope Ships without large deck openings Hull girder longitudinal stresses Hull girder shear stresses Ships with large deck openings Hull girder longitudinal stresses Hull girder shear stresses Equivalent stress Definitions of hull girder stress components Longitudinal stress Shear stresses...22 Section 4 Hull girder ultimate strength check Application General Checking criteria General Hull girder ultimate bending loads Hull girder ultimate bending capacity Part 3 Chapter 5 Contents Changes historic...27 Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 5
6 SECTION 1 STRENGTH CHARACTERISTICS OF HULL GIRDER TRANSVERSE SECTIONS Symbols For symbols not defined in this section, refer to Ch.1 Sec.4. 1 General 1.1 Scope This section specifies the criteria for calculating the hull girder strength characteristics. 2 Hull girder transverse sections 2.1 General Hull girder transverse sections shall be considered as being constituted by the members contributing to the hull girder longitudinal strength, i.e. all continuous longitudinal members. Part 3 Chapter 5 Section Structural members not contributing to hull girder sectional area The following members shall not be considered in the calculation as they are considered not contributing to the hull girder sectional area: superstructures extending less than 0.15 L deckhouses extending less than 0.15 L vertically corrugated bulkheads, according to [2.5] bulwarks and gutter plates bilge keels sniped or non-continuous longitudinal stiffeners non-continuous hatch coaming. 2.3 Continuous trunks and longitudinal continuous hatch coamings Continuous trunks and longitudinal continuous hatch coamings may be included in the hull girder transverse sections, provided that they are effectively supported by longitudinal bulkheads or primary supporting members. 2.4 Longitudinal stiffeners or girders welded above the strength deck Longitudinal stiffeners or girders welded above the strength deck, including the deck of any trunk fitted as specified in [2.3], shall be included in the hull girder transverse sections. 2.5 Longitudinal bulkheads with corrugations For longitudinal bulkheads with vertical corrugations, the vertical corrugations shall not be included in the hull girder transverse section. Longitudinal bulkheads with vertical corrugations are not effective for hull girder bending, but they are effective for hull girder shear force. Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 6
7 2.5.2 For the purpose of calculating the unit shear flow for hull girder vertical shear flow, q vi-gr, as defined in Sec.2 and q vi-n50, as defined in Sec.3 for vertical corrugations, the following reduction factor shall be used to obtain the effective thickness of the corrugation: where s c, a and c are defined in Ch.3 Sec.6 [5.1]. For the thickness applied in the hull girder shear capacity as given in Sec.2 [2.1], t i-gr and in the shear stress calculation as given in Sec.3 [4.2], t i-n50, this thickness reduction is not applicable. 2.6 Members in materials other than steel Where a member contributing to the longitudinal strength is made of a material other than steel having a Young s modulus, E different from N/mm 2, the steel equivalent sectional area that may be included in hull girder transverse section is obtained by applying the following factor: Part 3 Chapter 5 Section Definitions of openings The following definitions of openings shall be applied: a) Large openings are: elliptical openings exceeding 2.5 m in length or 1.2 m in breadth circular openings exceeding 0.9 m in diameter. b) Small openings (i.e. manholes, lightening holes, etc.) are openings that are not large ones. c) Isolated openings are openings spaced not less than 1 m apart in the ship s transverse/vertical direction. 2.8 Large openings Large openings shall be deducted from the sectional area used in hull girder moment of inertia and section modulus. 2.9 Isolated small openings Smaller openings (manholes, lightening holes, single scallops in way of seams etc.) need not to be deducted provided that the sum of their breadths or shadow area breadths in one transverse section does not reduce the section modulus at deck or bottom by more than 3% and provided that the height of lightening holes, draining holes and single scallops in longitudinals or longitudinal girders does not exceed 25% of the web depth, for scallops maximum 75 mm. A deduction-free sum of smaller openings breadths in one transverse section in the bottom or deck area equal to: may be considered equivalent to the above reduction in section modulus. Σb = total breadth of large openings, in m, at the transverse section being considered, determined as indicated in Figure 1. Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 7
8 Part 3 Chapter 5 Section 1 Figure 1 Calculation of Σb and Σb s 2.10 Lightening holes, draining holes and single scallops Lightening holes, draining holes and single scallops in longitudinals need not be deducted if their height is less than 0.25 h w, where h w is the web height of the longitudinals, in mm. Otherwise, the excess shall be deducted from the sectional area or compensated Non-continuous decks and longitudinal bulkheads When calculating the effective area in way of non-continuous decks and longitudinal bulkheads, the effective area shall be taken as shown in Figure 2. The shadow areas, which are not effective for hull girder bending but effective for hull girder shear force, are obtained by drawing two tangent lines with an angle of 15 deg to the longitudinal axis of the ship. Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 8
9 Part 3 Chapter 5 Section 1 Figure 2 Effective area in way of non-continuous decks and bulkheads 2.12 Longitudinal members with reduced effectiveness For hull girder cross sections where the beam theory is not applicable, the contribution of longitudinal members with reduced effectiveness, e.g. hatchway girders between the multi hatchways and upper decks of passenger ships, to the strength characteristics of the hull girder shall be determined by direct calculations. Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 9
10 SECTION 2 VERTICAL HULL GIRDER BENDING AND SHEAR STRENGTH Symbols For symbols not defined in this section, refer to Ch.1 Sec.4. C w f har I y-gr M sw = wave parameter as defined in Ch.4 Sec.4 = correction factor for harbour/sheltered water conditions to be taken as: f har = 0.5, unless otherwise defined in Pt.5 = gross moment of inertia, in m 4, of the hull transverse section about its horizontal neutral axis = permissible vertical still water bending moment, in knm, for hogging and sagging, in seagoing condition at the hull transverse section being considered as defined in Ch.4 Sec.4 [2.2.2] M wv = vertical wave bending moment, in knm, for hogging and sagging, in seagoing condition at the hull transverse section being considered as defined in Ch.4 Sec.4 [3.1.1] Q sw = permissible positive or negative still water shear force for seagoing operation, in kn, at the hull transverse section considered, as defined in Ch.4 Sec.4 [2.4.2] Q sw-p = permissible positive or negative still water shear force for harbour/sheltered operation, in kn, at the hull transverse section considered, as defined in Ch.4 Sec.4 [2.4.3] Q sw_lcd = vertical still water shear force for considered loading condition in seagoing operation, in kn, at the hull transverse section considered Q sw-lcd-p = vertical still water shear force for considered loading condition in harbour/sheltered operation, in kn, at the hull transverse section considered Q wv = positive and negative vertical wave shear force, in kn, for seagoing condition at the hull transverse section being considered, as defined in Ch.4 Sec.4 [3.2.1] Q R = total vertical hull girder shear capacity, in kn, at the hull transverse section being considered, as defined in [2.1] ΔQ mdf = shear force correction at the transverse section considered, in kn, if applicable as defined in [2.4] t i-gr = gross thickness, in mm, for plate i V D = vertical distance to the equivalent deck line, in m, as defined in [1.2.3] q vi-gr = unit shear flow for hull girder vertical shear force, in mm -1, for the plate i based on gross thickness t i-gr, in mm x z z D z n-gr = X coordinate, in m, of the calculation point with respect to the reference coordinate system defined in Ch.1 Sec.4 [3.6] = Z coordinate, in m, of the calculation point with respect to the reference coordinate system defined in Ch.1 Sec.4 [3.6] = Z coordinate, in m, of strength deck at ship side = Z coordinate, in m, of horizontal neutral axis of the hull transverse section with gross scantling defined in [1.2], with respect to the reference coordinate system defined in Ch.1 Sec.4 [3.6] Z B-gr = gross section modulus, in m 3, at bottom, to be calculated according [1.2] Z D-gr = gross section modulus, in m 3, at deck, to be calculated according [1.2]. Part 3 Chapter 5 Section 2 Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 10
11 1 Vertical hull girder bending strength 1.1 General Scantlings of all continuous hull girder longitudinal strength members based on section modulus requirement in [1.3] and moment of inertia requirement in [1.5] are generally to be maintained within 0.4 L amidships. However, in special cases, based on consideration of type of ship, hull form and loading conditions, the scantlings may be gradually reduced towards the end of the 0.4 L part, bearing in mind the desire not to inhibit the vessel's loading flexibility The k material factors shall be defined with respect to the materials used for the bottom and deck members contributing to the hull girder longitudinal strength according to Sec.1 [2]. When material factors for higher strength steels are used, the requirements in [1.6] apply The shiptype rules for container ships substitute some of the paragraphs in this section. Reference is made to Pt.5 Ch.2. (UR S11A) Part 3 Chapter 5 Section Definition of hull girder section modulus Section modulus at bottom The gross section modulus at bottom is obtained, in m 3, from the following formula: Section modulus at deck The gross section modulus at equivalent deck line is obtained, in m 3, from the following formula: Equivalent deck line When no effective longitudinal members specified in Sec.1 [2.3] and Sec.1 [2.4] are positioned above a line extending from strength deck at side to a position (z D z n-gr )/0.9 from the neutral axis at the centerline, the equivalent deck line is obtained, in m, from the following formula: When effective longitudinal members as specified in Sec.1 [2.3] and Sec.1 [2.4] are positioned above a line extending from strength deck at side to a position (z D z n-gr )/0.9 from the neutral axis at the centerline, the equivalent deck line is obtained, in m, from the following formula: y T, z T = Y and Z coordinates, in m, of the top of continuous trunk, hatch coaming, longitudinal stiffeners or girders, to be measured for the point which maximises the value of V D. Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 11
12 1.3 Minimum section modulus at midship part The gross section modulus, in m 3, at equivalent deck line as defined in [1.2.3], and bottom at midship part shall not be less than the value obtained from the following formula: f r = reduction factor related to service restrictions, defined in Ch.4 Sec Section modulus The gross section modulus related to deck or bottom, along the full length of the hull girder, from AE to FE, in m 3, shall comply with the following formula: Part 3 Chapter 5 Section 2 σ perm = permissible hull girder bending stress, in kn/m 2, to be taken as: for for for Intermediate values of σ perm shall be obtained by linear interpolation. For the ranges outside 0.4L midship the permissible hull girder stress may be particularly considered if longitudinal strength has been evaluated and found acceptable by finite element analysis. 1.5 Minimum moment of inertia at midship part Application The requirement in [1.5.2] applies to self propelled ships with length above 90 m Hull girder moment of inertia The gross moment of inertia about the horizontal axis, in m 4, at midship part shall not be less than the value obtained from the following formula: f r = reduction factor related to service restrictions, defined in Ch.4 Sec.3. Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 12
13 1.6 Extent of high tensile steel Vertical extent The vertical extent of higher strength steel, in m, used in the deck zone or bottom zone and measured respectively from the equivalent deck line at side specified in [1.2.3], or the baseline shall not be taken less than the value obtained from the following formula, see Figure 1: z 1 σ perm,i σ L-gr = distance from horizontal neutral axis to the equivalent deck line at side or baseline respectively, in m = permissible hull girder bending stress of the considered steel, in N/mm 2, as given in [1.4.1] and Figure 1 = hull girder bending stress, at the equivalent deck line at side or at baseline respectively, in N/mm 2, to be taken as: Part 3 Chapter 5 Section 2 based on the maximum absolute value of sagging and hogging vertical bending moment. Figure 1 Vertical extent of higher strength steel Longitudinal extent Where used, the application of higher strength steel shall be continuous over the length of the ship to the location where the longitudinal stress levels are within the allowable range for mild steel structure as shown in Figure 2. Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 13
14 Part 3 Chapter 5 Section 2 Figure 2 Longitudinal extent of higher strength steel 1.7 Permissible still water bending moments for harbour/sheltered water operations The permissible still water bending moments, in knm, for harbour/sheltered operations in hogging and sagging shall comply with the following criteria: The bending moment M wv used above shall be taken with the same sign as the considered bending moment M sw-p. 2 Vertical hull girder shear strength 2.1 Total hull girder shear capacity The total vertical hull girder shear capacity, in kn, is the minimum of the calculated values for all plates i contributing to the hull girder shear of the considered transverse section and shall be obtained by the following formula: τ i-perm = permissible shear stress, in N/mm 2, for plate i, to be taken as: Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 14
15 2.2 Seagoing condition The positive and negative permissible vertical still water shear force, in kn, for seagoing condition shall comply with the following criteria: The shear force Q wv used above shall be taken with the same sign as the considered shear force Q sw The vertical still water shear forces, in kn, for all loading conditions for seagoing condition shall comply with the following criteria: The shear force Q sw used above shall be taken with the same sign as the considered shear force Q sw-lcd. 2.3 Harbour/sheltered water operations Part 3 Chapter 5 Section The positive and negative permissible vertical still water shear force, in kn, for harbour/sheltered water operations shall comply with the following criteria: The shear force Q wv used above shall be taken with the same sign as the considered shear force Q sw-p The vertical still water shear forces, in kn, for all loading conditions for harbour/sheltered water operations shall comply with the following criteria: The shear force Q sw-lcd-p used above shall be taken with the same sign as the considered shear force Q sw-p. 2.4 Shear force correction Shear force correction, ΔQ mdf in kn, is defined as the difference between shear force on a shear panel determined from shear flow calculation and the actual shear force. Shear force correction results from shear force carrying longitudinal members and uneven transverse load distribution. Shear force correction shall be taken into account where relevant. Procedures for calculation of shear force correction are given in Pt.5 for each ship type. Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 15
16 SECTION 3 HULL GIRDER YIELD CHECK Symbols For symbols not defined in this section, refer to Ch.1 Sec.4. I y-n50 I z-n50 I T-n50 I ω-n50 M sw-h, M sw-s M st M wh-lc M wt-lc M wt-lc-max M wv-lc q vi-n50 Q sw-pos, Q sw-neg Q wv-lc S ωi-n50 t i-n50 x y z z n-n50 = net moment of inertia, in m 4, of the hull transverse section about its horizontal neutral axis = net moment of inertia, in m 4, of the hull transverse section about its vertical neutral axis = net torsional moment of inertia, in m 4, of the hull transverse section = net sectional moment of inertia, in m 6, of the hull transverse section = permissible vertical still water bending moment, in knm, for hogging and sagging respectively, in seagoing condition at the hull transverse section being considered as defined in Ch.4 Sec.4 [2.2.2] = design still water torsional moment in seagoing condition, in knm, at the hull transverse section being considered, as defined in Ch.4 Sec.4 [2.3.1], unless otherwise specified = horizontal wave bending moment, in knm, for a dynamic load case at the hull transverse section being considered, as defined in Ch.4 Sec.4 [3.5.4] = wave torsional moment, in knm, for a dynamic load case at the hull transverse section being considered, as defined in Ch.4 Sec.4 [3.5.5] = maximum absolute value of M wt-lc along the ship length = vertical wave bending moment, in knm, for a dynamic load case at the hull transverse section being considered, as defined in Ch.4 Sec.4 [3.5.2] = unit shear flow for hull girder vertical shear force, in mm -1, for the plate i based on t i-n50 = positive and negative permissible still water shear force for seagoing operation, in kn, at the hull transverse section being considered, as defined in Ch.4 Sec.4 [2.4.2] = vertical wave shear force in seagoing condition, in kn, for a dynamic load case at the hull transverse section being considered, as defined in Ch.4 Sec.4 [3.5.3] = net sectional moment of area, in m 3, of the hull transverse section = net thickness of plate i, in mm = X coordinate, in m, of the calculation point with respect to the reference coordinate system defined in Ch.1 Sec.4 [3.6] = Y coordinate, in m, of the calculation point with respect to the reference coordinate system defined in Ch.1 Sec.4 [3.6] = Z coordinate, in m, of the calculation point with respect to the reference coordinate system defined in Ch.1 Sec.4 [3.6] = Z coordinate, in m, of horizontal neutral axis of the hull transverse section with net scantlings, with respect to the reference coordinate system defined in Ch.1 Sec.4 [3.6]. Part 3 Chapter 5 Section 3 1 General 1.1 Scope This section provides the criteria for calculating the hull girder bending and shear strength in matters of the dynamic load cases as defined in Ch.4 Sec.2 [2]. The hull girder stresses as defined in [2] for ships without large deck openings and in [3] for ships with large deck openings are furthermore utilized for the following local assessments: hull local scantling assessment according to Ch.6 buckling assessment according to Ch.8 Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 16
17 fatigue assessment according to Ch.9 special requirements according to Ch Ships without large deck openings 2.1 Hull girder longitudinal stresses Definition For seagoing condition the hull girder longitudinal stress σ hg, in N/mm 2, induced by acting vertical and horizontal bending moments for a dynamic load case at the transverse section being considered is obtained from the following formula: σ hg-sw = Part 3 Chapter 5 Section 3 σ hg-dyn = σ wv-lc + σ wh-lc Design criteria Along the length L, the hull girder longitudinal stress σ hg, in N/mm 2, at any point being considered shall comply with the following criteria: σ hg-perm = permissible longitudinal stress, in N/mm 2, to be taken as: 2.2 Hull girder shear stresses Definition For seagoing condition the hull girder shear stress τ hg, in N/mm 2, induced by acting vertical shear forces for a dynamic load case at the transverse section being considered is obtained from the following formula: τ hg-sw = τ hg-dyn = τ wv-lc Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 17
18 2.2.2 Design criteria Along the length L, the hull girder shear stress τ hg, in N/mm 2, at any point being considered shall comply with the following formula: τ hg-perm = permissible shear stress, in N/mm 2, to be taken as: 3 Ships with large deck openings 3.1 Hull girder longitudinal stresses Definition For ships with large deck openings, as defined in Ch.1 Sec.4 Table 7, the additional longitudinal stresses induced by acting still water and wave torsional moments shall be considered. Hence, for the seagoing condition, the hull girder longitudinal stress σ hg, in N/mm 2, for a dynamic load case at the transverse section being considered is obtained from the following formula: Part 3 Chapter 5 Section 3 σ hg-sw = σ hg-dyn C ht = σ wv-lc + C ht σ wh-lc + σ wt-lc = reduction coefficient due combination with warping stress = Design criteria Along the length L, the hull girder longitudinal stress σ hg, in N/mm 2, at any point being considered shall comply with the following formula: σ hg-perm = permissible longitudinal stress, in N/mm 2, as defined in [2.1.2]. Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 18
19 3.2 Hull girder shear stresses Definition For ships with large deck openings, as defined in Ch.1 Sec.4 Table 7, the additional shear stress induced by acting still water and wave torsional moments shall be considered. Hence, for the seagoing condition, the hull girder shear stress τ hg, in N/mm 2, for a dynamic load case at the transverse section being considered is obtained from the following formula: τ hg sw = Part 3 Chapter 5 Section 3 τ hg dyn = τ wv LC + τ wt LC Design criteria Along the length L, the hull girder shear stress τ hg, in N/mm 2, at any point being considered shall comply with the following formula: τ hg-perm = permissible shear stress, in N/mm 2, as defined in [2.2.2]. 3.3 Equivalent stress Definition The equivalent stress, in N/mm 2, related to the hull girder longitudinal and shear stresses, σ hg and τ hg as defined in [3.1.1] and [3.2.1], respectively, at any point being considered is obtained from the following formula: Design criteria Along the length L, the equivalent stress, in N/mm 2, at any point being considered shall comply with the following formula: Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 19
20 σ v-perm = permissible equivalent stress, in N/mm 2, to be taken as: 4 Definitions of hull girder stress components 4.1 Longitudinal stress Longitudinal stresses induced by still water vertical hull girder bending The longitudinal stresses, in N/mm 2, induced by acting vertical still water bending moment in seagoing condition at the transverse section being considered, are obtained from the following formula: Part 3 Chapter 5 Section Longitudinal stresses induced by dynamic hull girder bending The longitudinal stresses, in N/mm 2, induced by acting vertical and horizontal wave bending moment for a dynamic load case and at the transverse section being considered, are obtained from the following formula: Longitudinal warping stresses induced by wave and still water hull girder torsion The longitudinal warping stress, in N/mm 2, induced by acting still water torsional moment in seagoing condition at the transverse section being considered, are obtained from the following formula: The longitudinal warping stress, in N/mm 2, induced by acting wave torsional moment for a dynamic load case and at the transverse section being considered, is obtained from the following formula: M σ-st = still water bi-moment related to longitudinal warping stress, in knm 2, at the transverse section being considered, in seagoing condition, to be taken as: Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 20
21 M σ-wt-lc ω i-n50 λ c d = dynamic bi-moment related to longitudinal warping stress, in knm 2, for a dynamic load case and at the transverse section being considered, to be taken as: = net sectorial coordinate, in m 2, of the point being considered = warping factor, in m -1, to be taken as: = distribution coefficient along the length L, to be taken as: for for for Part 3 Chapter 5 Section 3 for for x Α c LC l c = longitudinal distance, in m, between the aft end of the length L and the engine room front bulkhead, to be taken neither less than 0.15 L nor more than 0.25 L, see also Figure 1 = sign coefficient, to be taken as: C LC = -1 for OST-1S, OST-2P, OSA-1P and OSA-2S C LC = 1 for all other dynamic load cases = characteristic torsion length, in m, to be taken as: The bi-moments, M σ-st and M σ-wt-lc, are applicable to container ships with typical design. For other vessels (e.g. twin-island container ships and open hatch bulk carriers with wide cross decks) the bi-moments may be determined by direct calculations. Figure 1 Factor x A Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 21
22 4.2 Shear stresses Shear stresses induced by still water vertical hull girder shear force The shear stresses, in N/mm 2, induced by vertical still water shear force in seagoing condition at the transverse section being considered, are obtained from the following formulae: Shear stresses induced by dynamic vertical hull girder shear force The shear stress, in N/mm 2, induced by dynamic vertical shear force for a dynamic load case at the transverse section being considered is obtained from the following formula: Part 3 Chapter 5 Section Warping shear stresses induced by wave and still water hull girder torsion The warping shear stress, in N/mm 2, induced by still water torsional moment in seagoing condition at the transverse section being considered are obtained from the following formula: The warping shear stress, in N/mm 2, induced by wave torsional moment for a dynamic load case at the transverse section being considered is obtained from the following formula: M τ-st M τ-wt-lc = warping component of still water torsional moment related to warping shear stress induced by static torsion, in knm, at the transverse section being considered, in seagoing condition, to be taken as: M τ-st = M st = warping component of wave induced torsional moment related to warping shear stress induced by wave torsion, in knm, for a dynamic load case at the transverse section being considered, to be taken as: for for for for Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 22
23 c r c h M wt-lc-0.45l M wt-lc-0.6l = reduction coefficient, to be taken as: = reduction coefficient due to horizontal shear force, to be taken as: c h = 0.7 = to be taken as: M wt-lc at x = 0.45 L = to be taken as: M wt-lc at x = 0.6 L The warping components of torsional moments, M τ-st and M τ-wt-lc, are applicable to container ships with typical design. For other vessels (e.g. twin-island container ships and open hatch bulk carriers with wide cross decks) the warping components of torsional moments may be determined by direct calculations. Part 3 Chapter 5 Section 3 Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 23
24 SECTION 4 HULL GIRDER ULTIMATE STRENGTH CHECK Symbols For symbols not defined in this section, refer to Ch.1 Sec.4. M sw-h, M sw-s M wv 1 Application 1.1 General = permissible vertical still water bending moment in seagoing condition, in knm, at the hull transverse section being considered in hogging and sagging, as defined in Ch.4 Sec.4 [2.2.2] = vertical wave bending moment in seagoing condition, in knm, at the hull transverse section being considered in hogging and sagging, as defined in Ch.4 Sec.4 [3.1.1] This section applies to ships with all of the following characteristics: unrestricted service L > 150 m single deck or if required in Pt.5 for the considered ship type. Part 3 Chapter 5 Section The hull girder ultimate strength requirements given in [2.1.2] applies to the cargo fold area in general and to the following locations: in way of the forward end of the engine room in way of the forward end of the foremost cargo hold at any locations where there are significant changes in hull cross-section at any locations where there are changes in the framing system for ships with large deck openings such as container ships, locations at or near 0.25 L and 0.75 L The hull girder ultimate bending capacity shall be checked to ensure that it satisfies the criteria given in [2] For container ships the requirements in this section are supplemented by particular shiptype requirements in Pt.5 Ch.2. (UR S11A) 2 Checking criteria 2.1 General The vertical hull girder ultimate bending capacity shall be checked for hogging and sagging conditions for load components as defined in Table 1. Table 1 Load components Load components S+D Permissible still water bending moment, M sw-u M sw-h or M sw-s Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 24
25 2.1.2 The vertical hull girder ultimate bending capacity at any hull transverse section shall satisfy the following criteria: M = vertical bending moment, in knm, to be obtained as specified in [2.2.1] M U = vertical hull girder ultimate bending capacity, in knm, to be obtained as specified in [2.3.1] γ R = partial safety factor for the vertical hull girder ultimate bending capacity to be taken as: γ R = γ M γ DB γ M γ DB = partial safety factor for the vertical hull girder ultimate bending capacity, covering material, geometric and strength prediction uncertainties; in general, to be taken as: γ M = 1.1 = partial safety factor for the vertical hull girder ultimate bending capacity, covering the effect of double bottom bending, to be taken as: Part 3 Chapter 5 Section 4 for hogging condition: γ DB γ DB = 1.25 for vessels with empty cargo holds and class notation HC(A) or HC(B*), or HC(M) if alternate loading conditions are included in the loading manual = 1.1 for all other cases. for sagging condition: γ DB = Hull girder ultimate bending loads The vertical hull girder bending moment in hogging and sagging conditions, in knm, to be considered in the ultimate strength check shall be taken as: M sw-u γ S γ W = permissible still water bending moment, in knm, in hogging and sagging conditions at the hull transverse section considered as defined in Table 1 = partial safety factor for the still water bending moment, to be taken as: γ S = 1.0 = partial safety factor for the vertical wave bending moment, to be taken as: γ W = 1.2. Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 25
26 2.3 Hull girder ultimate bending capacity The ultimate bending moment capacities of a hull girder transverse section, in hogging and sagging conditions, are defined as the maximum values of the curve of bending moment capacity versus the curvature χ of the transverse section considered (see Figure 1). The curvature χ is positive for hogging condition and negative for sagging condition. Part 3 Chapter 5 Section 4 Figure 1 Bending moment capacity versus curvature χ The hull girder ultimate bending capacity, M U, shall be assessed by prescriptive method given in DNVGL- CG-0128 Buckling or by non-linear FE. Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 26
27 CHANGES HISTORIC July 2016 edition Main changes July 2016, entering into force as from date of publication Sec.2 Vertical hull girder bending and shear strength Sec.2: Q sw, Q sw-p, Q sw_lcd and Q sw-lcd-p are added to the list of symbols. Sec.2 [1.1.1]: The tapering requirement has been aligned with IACS UR S7. Sec.2 [1.5.2]: The formula for gross moment of inertia is corrected. Sec.3 Hull girder yield check Sec.3 [4]: The still water bi-moment related to warping normal stresses, the longitudinal distribution of dynamic bi-moment related to warping normal stresses and the longitudinal distribution of dynamic warping shear stresses are updated. October 2015 edition This is a new document. The rules enter into force 1 January Part 3 Chapter 5 Changes historic Amendments January 2016 Sec.1 Strength characteristics of hull girder transverse sections [2.5.2]: Clarification. Rules for classification: Ships DNVGL-RU-SHIP Pt.3 Ch.5. Edition January 2017 Page 27
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