Section 9 Superstructures, deckhouses and bulwarks

9.1.1 Where practicable, superstructures and deckhouses are to be designed with well cambered decks and well radiused corners to build rigidity into the structure.

9.1.2 The plating and supporting structure are to be suitably reinforced in way of localised areas of high stress such as corners of openings, cranes, masts, derrick posts, machinery, fittings and other heavy or vibrating loads.

9.1.3 Primary stiffening members are to be continuous and substantially bracketed at their end connections to maintain continuity of structural strength.

9.1.4 Secondary stiffening members are to be effectively continuous and bracketed at their end connections as appropriate.

9.1.5 Structures subject to concentrated loads are to be suitably reinforced. Where concentrations of loading on one side of a stiffener may occur, such as pillars out of line, the stiffener is to be adequately stiffened against torsion.

9.1.6 The plating thickness of superstructures, deckhouses and bulwarks is in no case to be less than the appropriate minimum requirement given in Pt 6, Ch 3, 2 Minimum thickness requirements.

9.1.7 Stiffener sections and geometric properties are to be in accordance with Pt 6, Ch 3, 1.18 Geometric properties and proportions of stiffener sections.

9.2.1 The term `house' is used in this Section to include both superstructures and deckhouses.

9.2.2 The symbols applicable to this Section are defined in Pt 6, Ch 3, 1.5 Symbols and definitions 1.5.1.

9.3.1 The thickness of house side plating is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating general using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate.

9.4.1 The thickness of the house front plating is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating general using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate.

9.5.1 The thickness of the house end plating is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating general using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate.

9.6.1 The thickness of the house top plating is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating general using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate.

9.7.1 The thickness of the coachroof plating is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating general using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate.

9.8.1 The thickness of the plating of machinery casings is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating general using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate.

9.9.1 The forecastle side plating may be a continuation of the hull side shell plating or fitted as a separate assembly. In both cases the plating thickness is to be the same as the side shell plating at deck edge. Where fitted as a separate assembly, suitable arrangements are to be made to ensure continuity of the effect of the sheerstrake at the break and at the upper edge of the forecastle side. Full penetration welding is to be used.

9.9.2 The side plating is to be stiffened by side frames effectively connected to the deck structure. Deep webs are to be fitted to ensure overall rigidity.

9.9.3 The deck plating thickness is to be increased by 20 per cent in way of the end of the forecastle if this occurs at a position aft of 0,25L _R from the FP. No increase is required if the forecastle end bulkhead lies forward of 0,2L _Rfrom the FP The increase at intermediate positions of end bulkhead is to be obtained by interpolation.

9.10.1 The Rule requirements for section modulus, inertia and web area for the house side primary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (a).

9.10.2 The Rule requirements for section modulus, inertia and web area for house side secondary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (b). Special consideration will be given to the application of other load models subject to the structural arrangement and degree of end fixity provided.

9.11.1 The Rule requirements for section modulus, inertia and web area for house front primary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (a).

9.11.2 The Rule requirements for section modulus, inertia and web area for house front secondary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (b). Special consideration will be given to the application of other load models subject to the structural arrangement and degree of end fixity provided.

9.12.1 The Rule requirements for section modulus, inertia and web area for house aft end primary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (a).

9.12.2 The Rule requirements for section modulus, inertia and web area for house aft end secondary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (b). Special consideration will be given to the application of other load models subject to the structural arrangement and degree of end fixity provided.

9.13.1 The house top is to be effectively supported by a system of transverse or longitudinal beams and girders. The span of the beams is in general not to exceed 2,4 m and the beams are to be effectively connected to the house upper coamings and girders.

9.13.2 The Rule requirements for section modulus, inertia and web area for house top primary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (a).

9.13.3 The Rule requirements for section modulus, inertia and web area for house top secondary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (b). Special consideration will be given to the application of other load models subject to the structural arrangement and degree of end fixity provided.

9.14.1 The Rule requirements for section modulus, inertia and web area for coachroof primary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (a).

9.14.2 The Rule requirements for section modulus, inertia and web area for coachroof secondary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (b). Special consideration will be given to the application of other load models subject to the structural arrangement and degree of end fixity provided.

9.15.1 The Rule requirements for section modulus, inertia and web area for machinery casing primary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (a).

9.15.2 The Rule requirements for section modulus, inertia and web area for machinery casing secondary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (b). Special consideration will be given to the application of other load models subject to the structural arrangement and degree of end fixity provided.

9.15.3 Where casing sides act as girders supporting decks, care is to be taken that access openings do not seriously weaken the structure. Openings are to be effectively framed and reinforced if found necessary. Particular care is to be paid to stiffening where the casing supports the funnel or exhaust uptakes.

9.15.4 Where casing stiffeners carry loads from deck transverses, girders, etc. or where they are in line with pillars below, they are to be suitably reinforced.

9.16.1 The scantlings of forecastle primary and secondary stiffening members are to be equivalent to those for the side shell envelope framing at the deck edge as required by Pt 6, Ch 3, 4 Shell envelope framing.

9.17.1 Superstructure first tier sides formed by extending the hull side structure are to be in accordance with the requirements for house fronts given in Pt 6, Ch 3, 9.4 House front plating and Pt 6, Ch 3, 9.11 House front stiffeners for plating and stiffeners respectively, but need not be taken as greater than the side structure requirements at the deck edge at the same longitudinal position.

9.18.1 The requirements for fire detection, protection and extinction are given in Pt 17 Fire Protection, Detection and Extinction.

9.19.1 All openings are to be substantially framed and have well rounded corners. Arrangements are to be made to minimise the effect of discontinuities in erections. Continuous coamings or girders are to be fitted below and above doors and similar openings.

9.19.2 Particular care is to be paid to the effectiveness of end bulkheads, and the upper deck stiffening in way, when large openings for doors and windows are fitted.

9.19.3 Special care is to be taken to minimise the size and number of openings in the side bulkheads in the region of the ends of erections within 0,5L _R amidships. Account is to be taken of the high vertical shear loading which can occur in these areas.

9.19.4 For closing arrangements and outfit the requirements are given in Pt 3, Ch 4 Closing Arrangements and Outfit.

9.20.1 Window openings are to be suitably framed and mullions will in general be required.

9.20.2 The scantlings of mullions are to be not less than as required for a stiffener in the same position.

9.20.3 When determining the stiffener requirements, the width of effective plating is in no case to be taken as greater than the distance between adjacent window openings.

9.20.4 Where significant shear forces are to be vertically transmitted by the window frames, adequate shear rigidity is to be verified by direct calculation.

9.21.1 Transverse rigidity is to be maintained throughout the length of the erection by means of web frames, bulkheads or partial bulkheads. Particular care is to be paid when an upper tier is wider than its supporting tier and when significant loads are carried on the house top.

9.21.2 Where practicable, web frames are to be arranged in line with bulkheads below.

9.21.3 Internal bulkheads are to be fitted in line with bulkheads or deep primary stiffeners below.

9.22.1 Adequate support under the ends of erections is to be provided in the form of webs, pillars, diaphragms or bulkheads in conjunction with reinforced deck beams.

9.22.2 Special attention is to be given to the connection of the erection to the deck in order to provide an adequate load distribution and avoid stress concentrations.

9.22.3 Connections between the erection and the deck by means of bimetallic joints are to comply with Pt 6, Ch 2, 4.23 Triaxial stress considerations.

9.22.4 Typical design details of house/deck connections are given in LR's Guidance Notes for Structural Details.

9.23.1 Sheathing arrangements are to comply with the requirements of Pt 6, Ch 3, 2.4 Sheathing.

9.24.1 For craft above 40 m in length, L _R, or for designs where the superstructure is designed to absorb global loads the effectiveness of superstructures to carry these loads is to be determined. The effectiveness may be assessed in accordance with Pt 6, Ch 6, 2.5 Torsional strength.

9.24.2 Where Pt 6, Ch 3, 9.17 Superstructures formed by extending side structures applies and the first or second tier is regarded as the strength deck according to Pt 6, Ch 6, 2.5 Torsional strength, the hull upper deck scantlings at the forward and aft ends of the superstructure may need to be increased due to the lesser efficiency of the superstructure tiers at their ends. The scantlings of the side structure in way of these areas may also be required to be increased.

9.24.3 When large openings or a large number of smaller openings are cut in the superstructure sides, reducing the capability to transmit shear force between decks, an assessment or structural efficiency may be required.

9.25.1 Direct calculations may be required to determine the plating and stiffener requirements where the house is of unusual design, form or proportions.

9.26.1 General requirements for bulwarks are given in Pt 3, Ch 4, 8 Bulwarks, guard rails and other means for the protection of crew.

9.26.2 The thickness of the bulwark plating is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating general using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate.

9.26.3 The requirements for section modulus, inertia and web area are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (d).

9.26.4 Bulwarks are not to be cut for gangway or other openings near the breaks of superstructures.

9.26.5 Attention is to be paid to avoid discontinuity of strength of the bulwark, particularly in way of local increases in stress and changes in height.

9.26.6 Welding of bulwark to the top edge of sheer-strake within 0,5L _R amidship, is generally to be avoided. However, if this arrangement is not practicable welding to the sheerstrake may be accepted if care is taken to minimise any notch effects.

9.26.7  Fishing craft are to have bulwarks fitted. The bulwark may be formed from a continuation of the side shell plating or connected as a separate assembly. Where the bulwark is considered to be stressed and contributing to the global strength of the craft, the plate thickness of the bulwark is not to be less than the sheer-strake thickness. In no case is the thickness of the bulwark plating to be taken as less than 80 per cent of the side shell thickness. The bulwark is to be supported by suitable stiffening members which may be formed from a continuation of the side frames, or from flanged plate stays of the same thickness as the bulwark. In general these frames are to be spaced not more than two side frame spacings apart.

9.26.8 In way of gantries, trawl gallows, mooring pipes etc. the plate thickness in way is to be increased by not less than 50 per cent.

9.26.9  Pilot craft are to be fitted with sufficient hand rails adjacent to the exposed areas of the working decks and platforms. In addition these areas are to have non-skid surfaces.

9.27.1 Requirements for freeing arrangements are given in Pt 3, Ch 4, 9 Deck drainage.

9.28.1 The requirements for the free flow area are given in Pt 3, Ch 4, 9.3 Free flow area.

9.29.1 The requirements for guard rails are given in Pt 3, Ch 4, 8.4 Guard rails.