Environmental Engineering Reference
In-Depth Information
AMERICAN BUREAU OF SHIPPING
ABS has been at the forefront of developing guidelines for the offshore oil
and gas energy sector since the industry's formative years, but it is a new-
comer to the offshore wind field. The ABS
Guide for Building and Class-
ing Offshore Wind Turbine Installations
(ABS 2010) was developed by
harmonizing ABS experience from offshore oil and gas platforms with the
guidelines provided in the IEC 61400 series of documents. Requirements
on the following subjects are specified in the guide for the support struc-
ture of a bottom-founded offshore wind turbine:
•
Classification, testing, and survey;
•
Materials and welding;
•
Environmental conditions;
•
Load case definitions;
•
Design of steel and concrete structures;
•
Foundations; and
•
Marine operations.
Requirements with regard to the survey during construction and instal-
lation and the survey after construction are generally in accordance with
established ABS rules for offshore structures. Alternative survey schemes
are also acceptable to account for the uniqueness of offshore wind tur-
bines, such as serial fabrication and installation.
Design environmental conditions and DLCs required by the ABS
guide are generally in agreement with those required by IEC 61400-3
but have a number of amendments, mainly to account for the effects
of tropical hurricanes in U.S. waters. The principle of site-specific
design is addressed in the definition of the DLCs in the guide. Envi-
ronmental conditions with a baseline return period of 100 years are
required to be considered for the extreme storm conditions (DLCs 1.6,
6.1, and 6.2). Furthermore, the omnidirectional wind condition is
required for turbines subject to tropical hurricanes, cyclones, and
typhoons (DLC 6.2).
The established ABS rules and guides for offshore structures, as well as
API RP 2A, have been discussed to provide a technical basis for the devel-
opment of support structure and foundation design criteria. The guide
specifies a set of design criteria for steel support structures by using a
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