CHAPTER 5 HULL STRUCTURE

5100. General

5101. Material

1. The main structural members in this chapter are to be of the hull structural rolled steels specified in "Rules for the Classification of Steel Ships" or equivalent.

2. Grade A steels specified in "Rules for Classification of Steel Ships" may be used for the main the main structural members of the dock. Grade D steels will, however, be required for the main struc- tural members such as the deck plates, shell plates and their girders within 0.4 Ã amid-length, where the thickness exceeds 30 mm.

3. If the dock is to be operated in a site with air temperatures regularly below 0℃ in the winter sea- son, the notch toughness of the steels will be given special consideration.

5102. Welding

Welding and we1d connections are to comply with the requirements of "Rules for the Classification of Steel Ships", as far as applicable to the docks. Alternatively, welding may be in accordance with another recognized standard provided all related requirements of the standard are also complied with.

5103. Corrosion protection

All external and internal surfaces of the hull structures except in oil tanks are to be protected against corrosion by paint of suitable composition or other effective means. Where special pro- tective coatings are applied to the external and internal surfaces, or other specially, effective meth- ods of corrosion control are adopted, reductions in scantlings will be specially considered.

5104. General construction

1. The requirements in this chapter apply to the steel docks of the following types :

(1) Caisson type; dock in which the bottom pontoon and both dock wings are continuous and inseparable.

(2) Sectional pontoon type; dock in which the dock wings are continuous and the bottom consists

of individual noncontinuous pontoons. The pontoons are permanently or detachably connected to the dock wings.

2. To avoid the excessive stress concentration, the structural members of the dock are to be con- tinuous as far as possible.

5200. Longitudinal Strength

5201. Longitudinal strength

The longitudinal strength of the dock is to be calculated for the most severe expected docking and transient loading conditions during normal operations. Such condition may be generally assumed that a ship having a weight equal to the maximum lifting capacity of the dock and the shortest ship's length expected is supported on the keel blocks, the center of the ship's length being positioned at the mid-length of the dock, and the freeboard at the pontoon deck is as described in 4102. The level of water ballast is to be constant over the length(Ã ). The level of compensating ballast water may, however, be determined with the normal operation manual where it is intended that normal operation of the dock is to be by differential ballast conditions by special agreement with the Society.

5202. Towing condition

Special consideration will be given to the longitudinal strength where it is intended to tow the dock in unprotected waters, including particulars of the season and the duration and area of the towing operation.

5203. Ship weight curve

The weight curve of the ship is to be taken as a rectangle with a superimposed parabola of half the area of the rectangle, the length of each area being ÃĊ.

5204. Allowable stresses

For the loading conditions defined in 5201. the longitudinal bending stresses are not to exceed 142 N/mm2 and the shear stresses are not to exceed 98 N/mm2.

5205. Section modulus

When calculating the section modulus of the hull structure, the sectional area of all effective con- tinuous longitudinal strength members are to be included. The section modulus of the hull structure at its mid-length is to be maintained within 0.4 Ã a mid-length of the dock, unless a1arger ex- tension or special strengthening is necessitated by the bending moment curve.

5206. Approximate formula of required section modulus

Notwithstanding the requirements of 5201., 5203. and 5204. the section modulus required for the hul1 structure may be generally determined from the formula where the lifting capacity of the dock is not exceeds 40,000 tons.

Ě Ņ ĪǾĮJÇÃ (cm2)

Ç : the maximum lifting capacity in tons 5207. Operation manual

Information on the loading conditions for the longitudinal strength is to be contained in the oper- ation manual. Where governing bending moments and/or shear forces may occur at less than the maximum lifting capacity, such conditions are to be investigated, and contained in the operation manual.

5208. Deflection control

The maximum allowable deflection of the dock is to be submitted for approval. This deflection is not to exceed that corresponding to a stress of 142 N/mm2 when lifting the ship defined in 5201. As for deflection monitoring measures, see 6200.

5300. Transverse Strength

5301. Loading condition

The transverse strength of the dock is to be calculated for the most severe expected docking and transient conditions during normal operations, and is to be examined at least for the conditions as follows;

(1) The docked ship conditions : as described in 5201. It is assumed that the docked ship mally is supported by the keel blocks only.

(2) The transient condition : the dock emerging out of water with a typical ship fully supported on

the blocks and the pontoon deck subjected to a waterhead just below top of docking blocks, with corresponding ballast water in the tanks.

5302. Allowable stress

Under the loading conditions in 5301. the compressive or tensile stresses in transverse members are not to exceed 170 N/mm2. The shear stresses in the transverse members are not to exceed 98 N/mm2.

5303. Approximate formula

Where the maximum lifting capacity of the dock does not exceed 40,000 tons, calculations of the

transverse strength defined in 5301. and 5302. may be omitted if the thickness tom plates of the pontoon is not less than that given below :

(1) Caisson type; obtained from the following formula.

of the top and bot-

LǾLLĨK Æ Ī (mm)

(2) Sectional pontoon type; given by the above(1) or obtained from the whichever is greater ;

following formula,

LǾLĮĮ × Ç ᾨᾬ Õ Ã ᾘᾬ (mm)

where:

Ç : the maximum lifting capacity in tons

ᾨᾬ : length of the sectional pontoon measured alongside the center line ters

ᾘᾬ : depth of the pontoon at the center in meters

of the dock in me-

5400. Structural Detail and Local Strength

5401. Structural arrangement

A centerline girder or longitudinal member is to provide adequate support for the keel blocks. Side girders or transverse members are to be arranged to support the side blocks.

5402. Buckling

The structural panels and members of the hull structures are to be adequately stiffened to vent buckling.

5403. Tank and shell plates

The thickness of the tank and shell plates is not to be less than obtained from the following formula. The minimum thickness is, however, to be 6.5 mm for the tank plates and 7 mm for the shell plates.

ĮǾĴ ĊΡ̓Üᾜ Ñ ÌǾJ (mm)

where:

Ċ : spacing of stiffeners, frames etc., in meters

ᾜ : 2.5 m or the followings, whichever is greater ; for tanks ;

vertical distance measured from the lower edge of plate to the mid-point of the distance between the top of tanks and the top of overflow pipes in meters. As an alternative the maximum differential head defined in 5407. may be used for the ballast tanks.

for cofferdams and void spaces;

vertical distance measured from lower edge of plate to the maximum immersion water line in meters.

5404. Tank stiffener and frame

The section modulus of tank stiffeners and frames is not to be less than obtained from the follow- ing formula;

ĴǾĴJ ǼĊ ᾜ ᾨĪ (cm3)

where:

Ċ : spacing of stiffeners, frames etc. in meters

ᾨ : span of stiffeners, frames etc. in meters

ᾜ : 2.5 m or the followings, which ever is greater; for tanks;

vertical distance measured from the mid-point of ᾨ for vertical stiffeners of Ċ for horizon- tal stiffeners to the midpoint of the distance between the top of tanks and the top of over- flow pipes in meters. As an alternative, the maximum differential head defined in 5407. may be used for the ballast tanks.

for cofferdams and void spaces;

vertical distance measured from the midpoint of ᾨ for vertical frames etc. or Ċ for longi- tudinal frames etc. to the maximum immersion water line in meters.

Ǽ : Coefficient given in Table 5.1, according to the type of end connections

Table 5.1 Values of Ǽ

5405. Girder, web frame etc.

1. The section modulus of the girders is not to be less than obtained from the following formula;

KǾÌĮ Ċ ᾜ ᾨĪ (cm3) where:

Ċ : breadth of the area supported by the girders in meters

ᾨ : span of the girders in meters

ᾜ : 2.5 m or the followings, which ever is greater

for tanks;

vertical distance measured from the mid-point of ᾨ for vertical girders etc. or Ċ for hori- zontal girders etc. to the mid-point of the distance between the top of tanks and the top

of overflow pipes in meters. As an alternative, the maximum differential head defined, in

5407. may be used for ballast tanks. for void spaces, cofferdams;

vertical distance measured from the mid-point of ᾨ for vertical web frames etc. or Ċ for horizontal web frames etc. to the maximum immersion water line in meters.

2. Thickness of girders is not to be less than obtained from the following formula.

ÌL ĊÌ (mm)

where:

ĊÌ : stiffener space or depth of girders, whichever is less in meters.

5406. Cross tie

The sectional area of cross ties, where fitted between the stiffeners, frames, girders, web frames etc. is not to be less than obtained from the following formula.

ĪǾĪ Ċ ᾎᾜ (cm3)

where:

Ċ : space of the stiffeners etc. supported by the cross tie in meters:

ᾎ : distance between the mid-point of two adjacent spans of stiffeners etc. supported by the cross tie in meters.

ᾜ : the maximum head in meters to be determined in accordance with the requirements of

5404. or 5405. as applicable.

5407. Maximum differential head

Where the maximum differential head is used for the design basis of the ballast tanks, hydrostatic data is to be submitted for approval to show the differential head based on the highest levels to which water will rise on each side of the structure in service. The differential head on the design is to be determined with a suitable margin to an actual differential head in service. Necessary data on operating the dock within such design limits are to be included in the operating manual.

5408. Top deck

1. Thickness of the top deck plates is not to be less than obtained from the following formula or 7 mm; whichever is greater.

ÌL Ċ (mm)

where:

Ċ : beam space (m)

2. Section modulus of the top deck beam is not to be less than obtained from the following formula.

Ǽ Ċ ᾨĪ (cm3) where:

Ǽ : 14.5 for longitudinal beam within 0.4 Ã amid-length,

5.4 for transverse beam and longitudinal beam at the fore and aft end.

For longitudinal beam other than the aforesaid, Ǽ may be gradually from 14.5 to 5.4.

Ċ : space of beam in meters

ᾨ : span of beam in meters

3. Section modulus of the transverse girder of the top deck is not to be less than obtained from the following formula.

ĴǾÌ ᾎ ᾨĪ (cm3) where:

ᾎ : breadth of the area supported by the girders in meters

ᾨ : span of girder in meters

5409. Safety deck

1. Scantlings of the safety deck as constructed as the tanks are to be in accordance with the require- ments defined in 5403., 5404. and 5405.

2. Scantling of the safety deck as constructed as other than the tanks are to be as follows;

(1) Thickness of the deck plates is not to be less than 6.5 mm or obtained from the following for- mula, whichever is greater.

ĮǾĶ Ċ Ρ̓Üᾜ Ñ ÌǾJ (mm)

where:

Ċ : beam space in meters

ᾜ : deck loads in t/m2

(2) Section modulus of the deck beam is not to be less than obtained from the following formula.

ĨǾĪ Ċ ᾜ ᾨĪ (cm3)

where:

Ċ : beam space in meters

ᾜ : deck loads in t/m2

ᾨ : span of beam in meters

(3) Section modulus of the deck girders is not to be less than obtained from the following formula.

ĨǾKJ ᾎ ᾜ ᾨĪ (cm3)

where:

ᾎ : breadth of the area supported by the girders in meters

ᾨ : span of the girder in meters

ᾜ : deck load in t/m2

5410. Non-water tight structures

The thickness of the web plates of the non-water tight structures such as the center girder, side girders and solid floors of the pontoon, and the non-water tight bulkheads, is not to be less than obtained from the following formula in general.

ÌL ĊÌ (mm)

where:

ĊÌ : space of stiffeners in meters

5411. Keel block and supporting structure

The keel blocks and their supporting structures are to be generally designed to the following loads;

Č Ņ ÌǾJ Ç Õ Ã (t/m)

where:

Č : loads to the keel blocks and supporting structures over the whole length of the dock.

Ç : the maximum lifting capacity of the dock in tons.

5412. Platforms

The minimum load on the platforms of dock ends is to be 5.88 kN/mm2, the factor of safety being not less than 4.

5413. Swing bridge The minimum load on

being not less than 4.

the swing bridge at dock ends is to be

3.92 kN/mm2,

the factor of safety