3 Stiffeners

3.1 General

3.1.1 All types of stiffeners (excluding web stiffeners) are to be connected at their ends. However, in special cases such as isolated areas of the ship where end connections cannot be applied, sniped ends may be permitted. Requirements for the various types of connections (bracketed, bracketless or sniped ends) are given in [3.2] to [3.4].

3.1.2 Where the angle between the web plate of the stiffener and the attached plating is less than 50 deg as shown on Figure 2, a tripping bracket is to be fitted. If the angle between the web plate of an unsymmetrical stiffener and the attached plating is less than 50 deg, the face plate of the stiffener is to be fitted on the side of open angle.

Figure 2 : Stiffener on attached plating with an angle less than 50 deg

3.2 Bracketed end connections of non-continuous stiffeners

3.2.1 Where continuity of strength of longitudinal members is provided by brackets, the alignment of the brackets on each side of the primary supporting member is to be ensured, and the scantlings of the brackets are to be such that the combined stiffener/bracket section modulus and effective cross sectional area are not less than those of the member.

3.2.2 At bracketed end connections, continuity of strength is to be maintained at the stiffener connection to the bracket and at the connection of the bracket to the supporting member.

3.2.3 The arrangement of the connection between the stiffener and the bracket is to be such that at no point in the connection, is the section modulus to be less than that required for the stiffener.

3.2.4 Net web thickness

The net bracket web thickness, t_b, in mm, is to comply with the following:

where:

Z : Net required section modulus, of the stiffener, in cm³. In the case of two stiffeners connected, Z is the smallest net required section modulus of the two connected stiffeners.

R_eH-stf : Specified minimum yield stress of the stiffener material, in N/mm².

R_eH-bkt : Specified minimum yield stress of the bracket material, in N/mm².

3.2.5 Brackets at the ends of non-continuous stiffeners

Brackets are to be fitted at the ends of non-continuous stiffeners, with arm lengths, _bkt, in mm, taken as:

_bkt is not to be taken less than:

• 
• 

where:

Z : Net required section modulus, for the stiffener, in cm³, as defined in [3.2.4].

t_b : Minimum net bracket thickness, in mm, as defined in [3.2.4].

For connections similar to item (b) in Figure 3, but not lapped, the bracket arm length is to comply with _bkt ≥ h_stf.

For connections similar to items (c) and (d) in Figure 3 where the smaller stiffener is connected to a primary supporting member or bulkhead, the bracket arm length is not to be less than two times of h_stf.

Figure 3: Bracket arm length of non-continuous stiffeners

3.2.6 Brackets with different arm lengths

The lengths of the arms, measured from the plating to the toe of the bracket, are to be such that the sum of them is greater than 2 _bkt and each arm not to be less than 0.8 _bkt, where _bkt is as defined in [3.2.5].

3.2.7 Edge stiffening of bracket

Where an edge stiffener is required, the web height of the edge stiffener, h_w, in mm, is not to be less than:

but not less than 50 mm.

where:

Z : Net section modulus, of the stiffener, in cm³, as defined in [3.2.4].

3.3 Bracketless connections

3.3.1 The design of bracketless connections is to be such as to provide adequate resistance to rotation and displacement of the connection.

3.4 Sniped ends

3.4.1 Sniped ends may be used where dynamic loads are small, provided the net thickness of plating supported by the stiffener, t_p, is not less than:

where:

P : Design pressure for the stiffener for the design load set being considered, in kN/m².

Sniped stiffeners are not to be used on structures in the vicinity of engines or generators in the machinery space, propeller impulse zone in the stern area nor on the shell envelope.

3.4.2 Bracket toes and sniped stiffeners ends are to be terminated close to the adjacent member. The distance is not to exceed 40 mm unless the bracket or member is supported by another member on the opposite side of the plating. Tapering of the sniped end is not to be more than 30 deg, where it is not practical to comply with this requirement, alternative arrangements are specially considered. The depth of toe or sniped end is, generally, not to exceed the thickness of the bracket toe or sniped end member, but need not be less than 15 mm.