Appendix 3-1 Material Selection

1. General

(1) For the classification of offshore fixed structures, it is necessary to take into account minimum excepted service temperature, the structural element category and material thickness when select- ing structural materials.

(2) The various parts of the structure are to be grouped according to their material application categories. The structural elements falling into these categories are described in general, in Par 3.

2. Classification of Application

The application of structural members in an offshore fixed structure is to be in accordance with the categories listed in this paragraph.

(1) Special application refers to highly stressed materials, located at intersections of main structural elements and other areas of high stress connection where the occurrence of a fracture could in- duce a major structural failure.

(2) Primary application refers to primary load carrying members of a structural where the occur-

rence of a fracture could induce a major structural failure.

(3) Secondary application refers to less critical members due to a combination of lower stress and favorable geometry or where an incidence of fracture is not likely to induce a major structural failure.

3. Examples of Applications

The following are typical examples of application categories.

(1) a Secondary Application Structure(Least Critical)

(A) Internal structure including bulkheads and girders in legs or columns

(B) Deck plating not essential for overall structural integrity

(C) Low stressed deck beams in parallel and bracing, except where structure is considered pri- mary or special application

(D) Plating of certain columns with low slenderness ratio, except at intersections

(2) Primary Application Structure(intermediate)

(A) Plating of lattice legs

(B) External shell plating of caissons

(C) Deck plating and structure which is not considered special or secondary

(D) Main braces, jacket legs and deck legs, except where considered special

(E) Heavy flanges and deep webs of major load supporting members, which from box or I type supporting structure, and which do not receive major concentrated loads

(F) Members which provide local reinforcement or continuity of structure in way of inter- sections, including main deck load plating where the structure is considered special applica- tion

(3) Special Application(Most Critical)

(A) External shell or deck structure in way of intersections of vertical columns

(B) Portions of deck plating, heavy flanges and deep webs at major load supporting members within the deck, which from box or I type supporting structure, and which receive major concentrated loads

(C) Intersection of major bracing members and critical joint nodes

(D) Members which receive immediate concentrated loads at intersections of major structural members

4. Steel Section Criteria

(1) Table 2-1 shows selection criteria for each structural element category for grades of normal and higher strength structural steel for hull specified in Pt 2, Ch 1 of Rules for Classification of Steel Ships.

(2) Selection of steel grades and thickness other than those shown in above (1) should be based on the fundamental principles specified in Table 2-1 and Ch 3, 201. 3.

Ch3 Materials and Welding Ch 3

Table 2-1 Steel Section Criteria

Ch3 Materials and Welding Ch 3