Assessment of Existing Structures and Repairs - Offshore Structures: Design, Construction and Maintenance - page 446

which change with climate change. This point is very critical and should be taken
into consideration during the assessment process.

7.2 API RP2A: HISTORICAL BACKGROUND
The history of the API standard for offshore structures is a very important consid-
eration in evaluating and assessing structures that have existed since the 1960s.
API was formed in 1919. API activity in the field of offshore structures was
initiated with the formation of the Committee on Standardization of Offshore
Structures. The committee s charge was to provide guidance that would

avoid problems and that could serve as the basis for future regulation for off-
shore structures.
RP2A was the first publication of the committee, and when it was issued in
1969 it was only 16 pages long. API RP2A is now on its twentieth edition, and
its alternative version, RP2A-LRFD, contains 224 pages. RP2A has always
been recognized as an evolving document, and every edition has stated in the
foreword that, as offshore knowledge continues to grow, recommended practice
will be revised.
From the beginning, API RP2A was intended not as a complete specifica-
tion, but as a supplement to other engineering codes and specifications. Further-
more, as more recent editions indicate, API RP2A is intended to supplement,
rather than replace, individual engineering judgment. Development of API
RP2A guidance is reviewed in the sections of this chapter for each of the
main topics.
For systems considerations, until recently API RP2A has been primarily
concerned with the design of every member separately. In the latest edition, a
separate subsection is devoted to structural redundancy, and the guidance on
framing patterns indicates consideration should be given to providing redun-
dancy in the structure and the framing system; substitute load paths are to be
preferred in design.
In the nineteenth edition (1991) of API RP2A, a section on the re-use of
platforms was added, and in the twentieth edition (1993) a separate section
on minimum structures was included. Minimum structures are defined as off-
shore structures that provide less redundancy than typical 4-legged template-
type platforms or free-standing caisson platforms. API RP2A illustrated that
the consequences of failure for minimum structures are usually lower than
for conventional structures. Therefore, API suggests that minimum structures
be checked by evaluating reserve strength and redundancy.

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7.2.1 Environmental Loading Provisions
According to Oto (1999), one of the most important topics in API RP2A is the
load effect due to environmental conditions; however, in early editions, the
guidance on this topic was the most brief.