API RP 2A-LRFD
Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms - Load and Resistance Factor Design
|Publication Date:||1 July 1993|
This "Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platforms - Load and Resistance Factor Design" (LRFD) contains the engineering design principles and good practices that have been the basis of the API RP2A working strength design (WSD) recommended practice, now in its 20th Edition. The LRFD provisions have been developed from the WSD provisions using reliability based calibration.
This recommended practice is based on sound engineering principies, extensive testing and field application experience. In no case is any specific recommendation included which could not be accomplished by presently available techniques and equipment. Consideration is given in all cases to the safety of personnel, compliance with existing regulations, and prevention of pollution.
This is the First Edition of the "Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platforms - Load and Resistance Factor Design." This practice has been approved by the API as an alternative to the 20th Edition of the REA "Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platforms."
The LRFD was first issued in December 1989 in draft form. It was consistent in most respects with the 18th Edition of the RP2A. The draft was open to comment for a period of two years. All of the comments received were carefully considered in the development of the First Edition. In general, the provisions are consistent with the 20th Edition of the RPZA.
The main changes in the First Edition from the draft are as follows:
• Sections A.6 and P have been inserted covering platform reuse. Other sections have been reworded to address reuse.
• The wave force section (C.3.2) has been totally revised and is consistent with the changes introduced into the WSD. Recalibration of the provisions was not felt to be necessary, since the same change is introduced into the calibration reference, e.g., the WSD.
• The wind force section (C.3.4) is now consistent with the WSD.
• The section on earthquake design of deck appurtenances and equipment (C.4.4.2) has been expanded.
• The section covering loads to be used in fabrication and installation (C.5) has been revised to address the problem of factoring various load types that inherently are self equilibrating. The solution is to use a common load factor in such cases.
• Section C.6 has been added that covers accidental loads.
• The scope of the recommendation for design of tubular members has been limited to D/t<300 and Fy<=414 mPa (60 Ksi). See Section D.1. This is consistent with WSD.
• Section G.7 has been inserted that covers soil reactions for axially loaded piles.
• Section P covering platform reuse has been added.
• Section Q covering minimum structures has been added.
• The prime units are now SI, with English units the secondary set.
In this practice, reference is made to ANSI/AWS D1.1- 92 Structural Welding code - Steel. While use of this edition is endorsed, the primary intent is that the AWS code be followed for the welding and fabrication of fixed Offshore Platforms. Chapters 8, 9 and 10 of the AWS Code give guidance that may be relevant to the design of fixed Offshore Platforms. This recommended Practice makes specific reference to Chapters 9 and 10 for certain design considerations. Where specific guidance is given in this API document, as in Sections E and F, this guidance should take precedence.
This standard shall become effective on the date printed on the cover but may be used voluntarily from the date of distribution.
As with all other API documents, this practice will be reviewed and changed periodically as required. Comments or suggestions on the LRFD should be sent to: American Petroleum Institute, 1201 Main Street, Suite 2535, Dallas TX 75202-3994. Attention: RP2A-LRFD