A discussion about specific research issues related to requalification of fixed steel structures will be given with main attention to the understanding of the structural effects associated with waves in the deck structure. The importance of this research in design of new structures will be emphasized. Furthermore, remedial measures to handle platforms with high probability of structural failure will be suggested, concentrating on consequence reducing measures.
Most of the world's inventory of platforms for offshore production of hydrocarbons are of the fixed steel jacket type. These platforms have been designed in accordance with the different issues of The American Petroleum Institute's Recommended Practice RP-2A (API-RP-2A). The latest issue of this recommended practice (20. issue in the Working Stress Design format, WSD-format, API, 1993a) is also prepared in a Load and Resistance Factor format, a LRFD-format (API, 1993b), serving as the basis for an international standard for the design of offshore fixed jacket steel structures (ISO, 1995). Most offshore platforms in use are, however, designed in accordance with earlier versions of these API recommendations and API has issued a separate recommendation (Chapter 17 of API-RP-2A, see API, 1993a) regarding requaliflcation of older platforms. Of particular concern are platforms designed to issues preceding the 9. issue (API, 1977). In relation to "older" platforms, important issues are related to treatment of improved knowledge regarding extreme values of the environmental loading (including effects of higher maximum waves), knowledge about the possible consequences of waves in deck, understanding of possible consequences of damages found during inspection and evaluation of the consequences of sea floor subsidence.
