API/ISO - American Petroleum Institute

Seismic Design Procedures and Criteria for Offshore Structures - FIRST EDITION
 N API RP 2EQ

Annotation

This standard contains requirements for defining the seismic design procedures and criteria for offshore structures and is a modified adoption of ISO 19901-2. The intent of the modification is to map the requirements of ISO 19901-2 to the United States' offshore continental shelf (U.S. OCS). The requirements are applicable to fixed steel structures and fixed concrete structures. The effects of seismic events on floating structures and partially buoyant structures are also briefly discussed. The site-specific assessment of jack-ups in elevated condition is only covered to the extent that the requirements are applicable.

This document defines the seismic requirements for new construction of structures in accordance with API 2A-WSD, 22nd Edition and later. Earlier editions of API 2A-WSD are not applicable.

The majority of the ISO 19901-2 document is applicable to the U.S. OCS. Where necessary, this document provides guidance for aligning the ISO 19901-2 requirements and terminology with API. The key differences are as follows.

a) API 2EQ adopts the ISO 19901-2 site seismic zones in lieu of those previously used in API 2A-WSD, 21st Edition and earlier.

b) Only the maps in Figure B.2 are applicable, in lieu of those previously used in API 2A-WSD, 21st Edition and earlier.

c) ISO 19901-2 seismic design approach is also adopted here with:

— a two-level seismic design in which the structure is designed to the ultimate limit state (ULS) for strength and stiffness and then checked to the abnormal or accidental limit state (ALS) to ensure that it meets reserve strength and energy dissipation requirements;