Civil Engineering Reference
In-Depth Information
the Den/HSE view on procedures and requirements for offshore construction,
installation and survey. For areas where no detailed guidance is given in
the notes, other codes and design standards are referenced, including API
and DNV.
New editions of the Guidance Notes have been published every five years or
so, and the latest edition, the fourth, was published in 1990. However, amend-
ments to the notes are issued as and when new information or guidance is avail-
able; seven amendments to the second edition and six amendments to the third
edition have been issued. In addition, background documents are published on a
frequent basis to supplement the guidance.
The notes contain guidance on a wide range of design considerations for off-
shore installations; some, like environmental loading, are covered in detail,
while other areas are only mentioned.
In general, it is important to mention that HSE guidance for extreme envir-
onmental conditions usually matches with United Kingdom (UK) regulatory
requirements, so it may be not useful in another global location. However,
the guidance on environmental loading in the notes has evolved progressively
to reflect new information and trends in design practice; more guidance and
indicative values of wave height were introduced into the second edition in
1977. The guidance on environmental considerations is both descriptive and
detailed, and the fourth edition in 1990 presents indicative values of most of
the important environmental design parameters.
The latest guidance on environmental loading is based on widely used
current practice, and for overall structural load it involves a package of inter-
dependent assumptions that are considered to provide estimates of sufficient
accuracy for design purposes.
7.3.1 Environmental Loading Provisions
The environmental loading sections in the Guidance Notes have evolved pro-
gressively to reflect new information and trends in design practice. In the latest
edition, guidance is given on all types of environmental effects influencing plat-
form loading, including: wind, waves, tides and currents, water depth, marine
growth, air and sea temperature and snow and ice accretion.
In the 1st Edition of
API RP2A (1969)
much of the hydrodynamic gui-
dance was discursive, but the 2nd Edition (1972) provided detailed guidance
which was given together with indicative values of the main parameters. It is
important to highlight that the guidance on environmental loading was vir-
tually unchanged in the second edition (1972), but was completely changed
and updated in the fourth edition. Therefore, in the assessment process it is
necessary to define the year of design and the edition of the code that was
followed.
The indicative values in the notes are intended for use only when site-
specific measurements or other authoritative studies are not available. The
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