Section 1 Materials

101. General

1. Application

(1) The requirements in this Chapter apply to the structural steels and materials for concrete con- struction intended to be used for the construction of offshore structure.

(2) The requirements, other than those specified in this chapter, are to be in accordance with the

related requirements of Pt 2, Ch 1 of Rules for Classification of Steel Ships.

(3) All materials used for a structure requiring Classification Survey during Construction are to be manufactured under approved method or under alternative process considered equivalent to the approved method and are to be adequate to the relevant requirements of the Rules.

(4) Upon request of attending Surveyor, data as to place of origin and results of relevant material tests for structural materials is to be submitted by the fabricator.

2. Steel Forming

(1) When forming changes base plate properties beyond acceptable limites, appropriate heat treat- ments are to be carried out to reestablish required properties. Unless approved otherwise, the ac- ceptable limits of the reestablished properties should meet the minimums specified for the origi- nal material before forming.

(1) The Society will survey formed members for their compliance with the forming dimensional tol- erances required by the design.

102. Structural steels

1. Application

This requirement covers specifications for materials used for the construction of offshore steel structures. It is not intended for metals used in reinforced or prestressed concrete.

2. Materials selection

(1) Materials used are required to exhibit satisfactory formability and weldability characteristics. As required, documentation is to be submitted to substantiate the applicability of a proposed steel.

(2) The requirements of (A) to (C) are to be considered as selection of materials.

(A) Toughness

Materials are to exhibit fracture toughness which is satisfactory for the intended application as supported by previous satisfactory service experience or appropriate toughness tests. Where the presence of ice is judged as a significant environmental factor, material selection

may require special consideration.

(B) Corrosion control

Details of corrosion control systems (such as coatings, sacrificial anodes or impressed current systems) are to be submitted with adequate supporting data to show their suitability. Such information is to indicate the extent to which the possible existence of stress corrosion, cor- rosion fatigue, and galvanic corrosion due to dissimilar metals to be considered. Where the

intended sea environment contains unusual contaminants, any special corrosive

effects of

such contaminants should also be considered. Appropriate coatings may be used to achieve satisfactory corrosion protection for miscellaneous parts such as bolts and nuts.

(C) Through thickness stress

In cases where through thickness properties relating to the structural

cial steel with improved through thickness properties specified in

Rules for Classification of Steel Ships may be required.

design, the use of spe-

Pt 2, Ch 1, 310. of

(3) Bolts and nuts are to have mechanical and corrosion characteristics comparable to the structural

elements being joined and are to be manufactured and tested in accordance with recognized ma- terial standards.

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3. Kinds of steels

(1) Steels are classified as specified in Table 2.1.1 and Table 2.1.2.

Table 2.1.1 Structural Steel Plates and Shapes

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Table 2.1.2 Structural steel pipes

(2) Steels other than those mentioned therein may be used, provided that their chemical composi- tion, mechanical properties and weldability are similar to those listed.

4. Mechanical properties

(1) Satisfactory mechanical properties can be demonstrated by any one of the following.

(A) Demonstration of past successful application, under comparable conditions, of a steel, pro- duced to a recognized standard. (such as those of the ASTM, API or other recognized standard)

(B) Demonstration that a steel manufactured by a particular producer using a specific manu- facturing process has minimum toughness levels representative of those listed Table 2.1.1

and Table 2.1.2.

(C) Charpy impact testing in accordance with Table 2.1.3.

(2) Impact tests

(A) Impact test temperature and absorbed energy of steels comply with Table 2.1.3.

(B) Energy values in Table 2.1.3 are minimum average values for full-size longitudinal speci- mens, Alternative toughness criteria which may be applied are as follows :

(a) Subsized longitudinal specimens :

To comply with Pt 2, Ch 1, Sec 2 of Rules for Classification of Steel Ships.

(b) Transverse specimens :

2/3 of the energy values shown in Table 2.1.3 but in no case less than 20 Â.

(c)

Longitudinal or transverse specimens: lateral expansion should not be less than 0.5 mm, or 0.38 mm, respectively

(d) Nil-ductility temperature (NDT) as determined by drop weight tests should be 5°C be- low the test temperature indicated in Table 2.1.3, notes (2).

(e)

Other fracture toughness

tests as appropriate by the Society.

(C) The minimum number of specimens to be tested per

number should be increased in accordance with usage

equivalent).

heat should be three; however, this of the material(see ASTM A673 or

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Table 2.1.3 Charpy impact tests

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5. Minimum Service Temperature

Minimum service temperature is generally to be established in accordance with (1) to (3) below. This temperature is to be based on meterological data taken over a period of not less than 10 years for the lowest average daily temperature.

(1) Material below the Splash Zone

For material below the Splash Zone below the splash zone, the service temperature is defined as 0°C. A higher service temperature maybe used where deemed appropriate by the Society.

(2) Material within or above the Splash Zone

For material within or above the splash zone the service temperature is the same as the lowest average daily atmospheric temperature. A higher service temperature may be used if the material above the waterline is warmed by adjacent sea water temperature or by auxiliary heating.

(3) Special Conditions

In all cases where material temperature is reduced by localized cryogenic storage or other cool-

ing conditions, such factors should be taken into account in establishing minimum service temperature.

103.Materials for Concrete Construction

1. Genera1

(1) Application

This subsection covers specifications for materials for concrete used in the construction of off- shore platforms. It includes the metals used in reinforced or prestressed concrete. All materials are to be suitable for intended service conditions and are to be of good quality, defined by rec- ognized specifications and free of injurious defects. Materials used in the construction of con- crete structures are to be selected with due attention given to their strength and durability in the marine environment.

(2) Zones

Particular attention should be given in each of the following zones.

(A) Submerged zone

chemical deterioration of the concrete, corrosion of the reinforcement and hardware, and abrasion of the concrete

(B) Splash zone

freeze-thaw durability, corrosion of the reinforcement and hardware, chemical deterioration of the concrete, and fire hazards

(C) Ice zone

freeze-thaw durability, corrosion of the reinforcement and hardware, chemical deterioration of the concrete, fire hazards, and abrasion of the concrete

(D) Atmospheric zone

freeze-thaw durability, corrosion of reinforcement and hardware, and fire hazards

2. Cement

(1) Type

Cement is to be equivalent to Types I or II Portland cement as specified by ASTM C150 or

portland-pozzolan cement as specified by ASTM C595. ASTM C150 Type III Portland cement may be specially approved for particular applications by the Society.

(2) Tricalcium Aluminate

The tricalcium aluminate content of the cement is generally to be in the 5% to 10% range.

(3) Oil Storage

For environments which contain detrimental sulfur bearing materials (such as where oil storage is planned and the oil is expected to contain sulphur compounds which are detrimental to con- crete durability), the maximum content of tricalcium aluminate is to be at the lower end of the 5 % to 10 % range. Alternatively, pozzolans or pozzolans and fly ash may be added or a suit- able coating employed to protect the concrete.

3. Water

(1) Cleanliness

Water used in mixing concrete is to be clean and free from injurious amounts of oils, acids, al- kalis, salts, organic materials or other substances that may be deleterious to concrete or steel.

(2) Nonpotable Water

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If nonpotable water is proposed for use, the selection of proportions of materials in the concrete is to be based on test concrete mixes using water from the same source. The strength of mortar test cylinders made with nonpotable water is not to be less than 90 % of the strength of similar cylinders made with potable water. Strength test comparisons should include 7-day and 28-day strength data on mortars prepared and tested in accordance with recognized standards such as ASTM C 109.

4. Chloride or Sulphide Content

(1) Water for structural concrete or grout should not contain more than 0.07 % chlorides as Cl by weight of cement, nor more than 0.09 % sulfates as SO4 when tested by ASTM D 512. Chlorides in mix water for prestressed concrete or grout should be limited to 0.04 % by weight of cement.

(2) Total chloride content, as CI, of the concrete prior to exposure shall not exceed 0.10 % by

weight of the cement for normal reinforced concrete and 0.06 % by weight of cement for pre- stressed concrete.

5. Aggregates

(1) General

Aggregates are to conform to the requirements of ASTM C 33 or equivalent. Other aggregates may be used if there is supporting evidence that they produce concrete of satisfactory quality. When specially approved, lightweight aggregates similar to ASTM C 330 may be used for con- ditions that do not pose durability problems.

(2) Washing

Marine aggregates are to be washed with fresh water before use to remove chlorides and sul- phates so that the total chloride and sulphate content of the concrete mix does not exceed the limits defined in 102. 4.

(3) Size

The maximum size of the aggregate is to be such that the concrete can be placed without voids. It is recommended that the maximum size of the aggregate should not be larger than the smallest of the following.

(A) one-fifth of the narrowest dimension between sides of forms

(B) one-third of the depth of slabs

(C) three-fourths of the minimum clear spacing between individual reinforcing bars, bundles of bars, prestressing tendons or post-tensioning ducts.

6. Admixtures

(1) General

The admixture is to be shown capable of maintaining essentially the same composition and per- formance throughout the wok as the product used in establishing concrete proportions. Admixtures containing chloride ions are not to be used if their use will produce a deleterious concentration of chloride ions in the mixing water.

(2) Recognized Standards

Admixtures are to be in accordance with applicable recognized standards such as ASTM C 260, ASTM C 494, ASTM C 618 or equivalents.

(3) Pozzolan Content

Pozzolan or pozzolan and fly ash content is not to exceed 15% by weight of cement unless specially approved.

7. Steel Reinforcement

Steel reinforcement used in offshore concrete structures is to be suitable for its intended service and in accordance with recognized standards.

(1) Reinforcement for Non-Prestressed Concrete

Non-prestressed reinforcement is to be in accordance with one of the following specifications or its equivalents.

(A) Deformed reinforcing bars and plain bars: ASTM A 615

(B) Bar and rod mats: ASTM A 184

(C) Plain wire for spiral reinforcement: ASTM A82, ASTM A 704

(D) Welded plain wire fabric: ASTM A 185

(E) Deformed wire: ASTM A 496

(F) Welded deformed wire fabric: ASTM A 497

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(2) Welded reinforcement

Reinforcement which is to be welded is to have the properties needed to produce satisfactory welded connections. Welding is to be in accordance with Pt 2, Ch 2 of Rules for Classification of Steel Ships.

(3) Steel Reinforcement for Prestressed Concrete

Steel reinforcement for prestressed concrete is to be in accordance with one of the following specifications or equivalent.

Seven-wire strand : ASTM A416, Wire : ASTM A 42

(4) Other prestressing tendons may be approved upon presentation of evidence of satisfactory properties.

8. Concrete

The concrete is to be designed to assure sufficient strength and durability. A satisfactory method for quality control of concrete is to be used which is equivalent to ACI 318. Mixing, placing and curing of concrete shall conform to recognized standards.

9. Water-Cement Ratio

Unless otherwise approved, water-cement ratios and 28-day compressive strengths of concrete for the three exposure zones are to be in accordance with Table 2.1.4.

Table 2.1.4 Water/Cement(W/C) Ratios and Compressive Strength

10. Other Durability Requirements

(1) Cement

Minimum cement content should insure an adequate amount of paste for reinforcement pro- tection and generally be not less than 355 kgĤmĖ.

(2) Freeze-Thaw Durability

When freeze-thaw durability is required, the concrete is to contain entrained air in accordance with a recognized standard such as ACI 211.1. Attention is to be paid to the appropriate pore distribution of the entrained air and the spacing between pores in the hardened concrete. The calculated spacing factors are not to exceed 0.25 mm.

(3) Scouring

When severe scouring action is expected, the coarse aggregate should be as hard as the material causing the abrasion, the sand content of the concrete mix should be kept as low as possible, and air entrainment is to be limited to the minimum appropriate to the application.

11. Grout for Bonded Tendons

(1) General

Grout for bonded tendons is to conform to ACI 318 or equivalent.

(2) Chlorides and Sulphates

Grout is not to contain chlorides or sulfates in amounts which are detrimental to the structure Limitations are included in 103. 4.

(3) Contents

Grout is to consist of Portland cement and potable water, or Portland cement, sand, and potable water. Admixtures may be used only after sufficient testing to indicate that their use is benefi-

cial and that they are free of harmful quantities of chlorides, nitrates, sulfides, sulphates or any

other material which has been shown to be detrimental to the steel or grout.

(4) Sand

Sand, if used, is to conform to ASTM C144 or equivalent, except that gradation may be modi- fied as necessary to obtain increased workability.

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(5) Preparation

Proportions of grouting materials are to be based on results of tests on fresh and hardened grout prior to beginning work. The water content shall be the minimum necessary for proper placement but in no case more than 50 % of the content of cement by weight. Grout is to be properly mixed and screened.

(6) Temperature

Temperature of members at the time of grouting is to be above 10°C and is to be maintained at this temperature for at least 48 hours.

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