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13. Framing design

13.1 The framing supporting the shell is separated into three different categories, transverse, longitudinal and oblique, the requirements for each form of framing are given in sections 18, 19 and 20 respectively.

13.2 The orientation and scantlings of a member are to be determined at the mid-point of the span of the part.

13.3 A transverse framing member, is a member, that when viewed from a point normal to the shell at the midpoint of the span, is at right angles to or within 20 degrees of being at right angles to a water plane parallel to the design ice load waterline.

13.4 A longitudinal framing member is a member that when viewed from a point normal to the shell at the midpoint of the span, is parallel to or is within 20 degrees of parallel to the chord of the water-line.

13.5 An oblique framing member is any framing member that is not a transverse or longitudinal framing member.

14. Load shape for framing ^

14.1 Subject to paragraph 14.3, the length of the design ice load LDL along the chord of the water-line is obtained from the formula:-

metres

where
"" is the displacement in thousands of tonnes; and

"P" is the total shaft power in megawatts.

14.2 Subject to paragraph 14.3, the vertical extent in metres of the design ice load VP on the chord of the shell at right angles to the water-line is to be taken as one eighth of .

14.3 For the minimum framing design in accordance with sections 18.3 and 19.4 the design load length is taken as 6.0 metres and VP is taken as 0.75 metres

Figure 7 ^
Illustration of stiffener angles

ENLARGE IMAGE

15. Stiffener design pressure ^

15.1 The design pressure PAV is obtained whereX < 0.2 from

MPa

and, where X ³ 0.2 from

MPa

where
X being DPH or DPT as is appropriate, and is the ratio of the portion under consideration of length S to the total length of the ice print LDL, as shown in Table 6, see sections 18.1 and 19.1 .

16. Brackets ^

16.1 An effective bracket at the end of any framing member is a bracket with a thickness not less than the greater of the thickness of the web; and

millimetres

in the case of brackets not fitted with a flange; or

millimetres

in the case of brackets fitted with a flange

where "K" is the minimum throat dimension of the bracket in millimetres; and

"ƒy" is the nominal yield stress of the steel in megapascals.

16.2 The total length of effective brackets on any framing member must not exceed 50 per cent of the moulded span.

17. Span of members ^

The application of the following two sections is defined in those sections which permit reductions in span.

17.1 Where effective brackets are fitted at the ends of a framing member, the span of the member may be measured

• when the free edge of the bracket makes an angle of less than 45 degrees to a framing member, from the point where a line drawn from the top of the bracket intersects the top of the framing member at 45 degrees; and
• when the free edge of the bracket makes an angle equal to or greater than 45 degrees to a framing member, from the toe of the bracket.

17.2 Where effective brackets are fitted at the ends of a framing member, the span of the member may be may be reduced by two thirds of the shortest leg length of the bracket.

18. Transverse framing ^

18.1 The design parameter DPT for determining the design pressure PAV from Table 6 for transverse main frames and web frames is obtained from the formula:-

where

"S" is the greatest moulded spacing between adjacent frames in metres which is

• measured normal to the moulded lines of the frames on the chord of the moulded surface of the shell, and
• at the mid point on the span or, where there is curvature of the frame line, at the point where the frame line is parallel to the chord of the span; and
• "" is the appropriate horizontal length of the design ice load from section 14.

18.2 Subject to section 18.3, for transverse main frames and web frames the shear area must not be less than that obtained from the formula:-

centimetres2

and the plastic section modulus must not be less than that obtained from the formula:-

centimetres3

where
"AsT" is the shear area defined in Section 21;

"CF" is a factor for the Category from Table 5;

"AF" is a factor for the area of the hull area in question obtained from Table 2;

"PAV" is the design pressure obtained from Table 6;

"R1" is a factor obtained from Table 7 according to the ratio of VP to the span (LS) to be used determining shear area of the frame;

"VP" is the vertical height of the design ice load from section 14.2;

"S" is the greatest spacing between adjacent frames in metres which is

• measured normal to the moulded lines of the frames on the chord of the moulded surface of the shell,
• at the mid point on the span but
• it is not to be taken as greater than LDL;

"R2" is a factor for load distribution based on load shape and is equal to 0.83;

"H" equals

• 15000 for tee and angle sections complying with sections 23.1, 23.2, 23.4, 23.6 and 23.7, and
• 17320 for all other sections;

"fy" is the nominal yield strength of the steel in megapascals;

"Zp" is the plastic section modulus defined in Section 22;

"LDL" is the length of the design ice load from section 14.1 in metres;

"LS" is the span in metres to be used in deriving the factor A from Table 7 and is, subject to section 17.1, the moulded span measured along the chord of the moulded line of the shell;

"LB" is, subject to section 17.2, the moulded span in metres measured along the chord of the moulded line of the shell; and

"B" is a term for the relationship between VP and LB and

when VP £ LB, is equal to

metres,

and when VP > LB, is equal to

metres.

18.3 Notwithstanding section 18.2 the shear area of transverse main frames and web frames must not be less than that obtained from the formula:-

centimetres2

and the plastic section modulus must not be less than that obtained from the formula:

where
"AsT " is the shear area defined in Section 21;

"AF" is a factor for the area of the hull area in question obtained from Table 2;

"PAV" is the design pressure obtained from Table 6;

"R1" is a factor R obtained from Table 7 according to the ratio of VP to the span (LS) to be used determining shear area of the frame;

"VP" is the vertical height of the design ice load from section 14;

"S" is the greatest spacing between adjacent frames in metres which is

• measured normal to the moulded lines of the frames on the chord of the moulded surface of the shell,
• at the mid point on the span but
• it is not to be taken as greater than LDL;

"R2" is a factor for load distribution based on load shape, and is equal to 0.83;

"H" equals

• 15000 for tee and angle sections complying with sections 23.1, 23.2, 23.4, 23.6 and 23.7, and
• 17320 for all other sections;

"fy" is the nominal yield strength of the steel in megapascals;

"Zp" is the plastic section modulus defined in Section 22;

"LDL" is the horizontal length of the design ice load from section 14.3;

"LS" is the span to be used in deriving the factor R from Table 7 and is, subject to section 17.1, the moulded span measured along the chord of the moulded line of the shell;

"LB" is, subject to section 17.2, the moulded span measured along the chord of the moulded line of the shell;

"B" is a term for the relationship between VP and LB equal when VP £ LB to

metres

and, when VP > LB to

metres;

and
"C" equals 1.0 for CAC1, CAC2 and CAC3 and 0.8 for CAC4.

Table 7 ^
Frame Factors

	Factor Facteur R		Factor Facteur R		Factor Facteur R		Factor Facteur R
0.02	0.99	0.8	0.68	2.2	0.37	4.2	4.2
0.1	0.95	0.9	0.65	2.4	0.35	4.6	4.6
0.2	0.90	1.0	0.62	2.6	0.33	5.0	5.0
0.3	0.86	1.2	0.56	2.8	0.31	6.0	6.0
0.4	0.82	1.4	0.52	3.0	0.29	7.0	7.0
0.5	0.78	1.6	0.47	3.2	0.27	8.0	8.0
0.6	0.74	1.8	0.44	3.6	0.25	9.0	9.0
0.7	0.71	2.0	0.40	4.0	0.23	10.0	10.0

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