Section 3 Secondary member end connections
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Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Ships, July 2022 - Part 3 Ship Structures (General) - Chapter 10 Welding and Structural Details - Section 3 Secondary member end connections

Section 3 Secondary member end connections

Parent topic: Chapter 10 Welding and Structural Details

3.1 General

3.1.1 Secondary members, that is longitudinals, beams, frames and bulkhead stiffeners forming part of the hull structure, are generally to be connected at their ends in accordance with the requirements of this Section. Where it is desired to adopt bracketless connections, the proposed arrangements will be individually considered.

3.1.2 Where end connections are fitted in accordance with these requirements, they may be taken into account in determining the effective span of the member.

3.1.3 Where the section modulus of the secondary member on which the bracket is based (see Pt 3, Ch 10, 3.3 Basis for calculation 3.3.2) exceeds 2000 cm3, the scantlings of the connection will be considered.

3.2 Symbols

3.2.1 The symbols used in this Section are defined as follows:

a, b = the actual lengths of the two arms of the bracket, in mm, measured from the plating to the toe of the bracket
b f = the breadth of the flange, in mm
t = the thickness of the bracket, in mm
Z = the section modulus of the secondary member, in cm3.

3.3 Basis for calculation

3.3.1 Where a longitudinal strength member is cut at a primary support and the continuity of strength is provided by brackets, the scantlings of the brackets are to be such that their section modulus and effective cross-sectional area are not less than those of the member. Care is to be taken to ensure correct alignment of the brackets on each side of the primary member.

3.3.2 In other cases the scantlings of the bracket are to be based on the modulus as follows:

  1. Bracket connecting stiffener to primary member:
    modulus of the stiffener.

  2. Bracket at the head of a main transverse frame where frame terminates:
    modulus of the frame.

  3. Brackets connecting lower deck beams or longitudinals to the main frame in the forward 0,15L:
    modulus of the frame.

  4. Elsewhere: the lesser modulus of the members being connected by the bracket.

3.3.3 Typical arrangements of stiffener end brackets are shown diagrammatically in Figure 10.3.1 Diagrammatic arrangements of stiffener end brackets.

3.4 Scantlings of end brackets

3.4.1 The lengths, a and b, of the arms are to be measured from the plating to the toe of the bracket and are to be such that:

  1. a + b ≥ 2,0

  2. a ≥ 0,8

  3. b ≥ 0,8

    where

    but in no case is l to be taken as less than twice the web depth of the stiffener on which the bracket scantlings are to be based.

    The scantlings of main frames are normally to be based on these standard brackets at top and bottom, while the scantlings of `tween deck frames are normally to be based on a standard bracket at the top only. Where the actual arm lengths fitted, a 1 and b 1(in mm) are smaller than Rule size, or bracket is omitted, an equivalent arm length, a, for the calculation of end connection factor, see Table 1.6.3 Shell framing (transverse), is to be derived from:

  4. a =

  5. a 1 ≥ 0,8 a

  6. b 1 ≥ 0,8 a

  7. a = 0, where:

    1. bracket is omitted from the upper or lower ends of the frame, or

    2. lower frame bracket at bilge is at same level as the inner bottom, or

    3. lower frame is welded directly to the inner bottom.

3.4.2 The length of arm of tank side and hopper side brackets is to be not less than 20 per cent greater than that required above.

3.4.3 The thickness of the bracket is to be not less than as required by Table 10.3.1 Thickness of brackets.

3.4.4 The free edge of the bracket is to be stiffened where any of the following apply:

  1. The section modulus, Z, exceeds 2000 cm3.

  2. The length of free edge exceeds 50t mm.

  3. The bracket is fitted at the lower end of main transverse side framing.

3.4.5 Where a flange is fitted, its breadth is to be not less than:

= but not less than 50 mm

3.4.6 Where the edge is stiffened by a welded face flat, the cross-sectional area of the face flat is to be not less than:

  1. 0,009b f t cm2 for offset edge stiffening.

  2. 0,014b f t cm2 for symmetrically placed stiffening.

Figure 10.3.1 Diagrammatic arrangements of stiffener end brackets

Table 10.3.1 Thickness of brackets

Bracket Thickness, in mm Limits
    Minimum Maximum
With edge stiffened:        

(a) in dry spaces

 6,5   12,5

(b) in tanks

 7,5
See Note 		  13,5

Unstiffened brackets:

(a) in dry spaces
7,5 –  

(b) in tanks

 8,5
See Note 		–  

Note In the cargo tank region of tankers, the minimum thickness is to be not less than the compartment minimum thickness, see Pt 4, Ch 9, 10 Construction details and minimum thickness.

3.4.7 Where the stiffening member is lapped on to the bracket, the length of overlap is to be adequate to provide for the required area of welding. In general, the length of overlap should be not less than , or the depth of stiffener, whichever is the greater.

3.4.8 Where the free edge of the bracket is hollowed out, it is to be stiffened or increased in size to ensure that the modulus of the bracket through the throat is not less than that of the required straight edged bracket.

3.5 Arrangements and details

3.5.1 The arrangement of the connection between the stiffener and the bracket is to be such that at no point in the connection is the modulus reduced to less than that of the stiffener with associated plating.

3.5.2 The design of end connections and their supporting structure is to be such as to provide adequate resistance to rotation and displacement of the joint.

3.5.3 For arrangements where end brackets are not perpendicular to the adjacent plating the strength of the brackets, in terms of lateral stability, may need to be specially considered.

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