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Interpretation of Results of Evaluation and Selection of Structural Elements for Survey : Ika A, Ika B, Ivana C Platforms

Supervising and health monitoring of any kind of structure is a new field that has been opened to be of increasing importance with regard to control durability, stability and safety as well as to estimate the life span of structure. A minimum strength capacity of is considered appropriate for contemporary offshore platforms in order to provide a safety from any expected or unanticipated loads. Such provision also ensures a minimum standard for connections of particular members that take on primary importance in reserve strength assessments of the whole structure. Recording the actual situation is directed towards reliable information about on the on-site structure and particular structural element. According to the task defied for the offshore platforms IKA A, B and IVANA C there was a request for selection of structural elements jacket & deck where it is necessary to perform monitoring and survey according to ISO standards ISO/CD 19902 and recommendations of American Petroleum Institute described in « API RECOMMENDED PRACTICE 2A-WSD (RP 2A-WSD)» , 21st ed., Dec. 2000. As the basic documents for the platform IKA A « JACKET - IN SERVICE ANALYSIS» and « DECK - IN SERVICE ANALYSIS» have been used. The observed documents for platforms IKA B and IVANA C are included in « MONOPOD - STRUCTURAL IN SERVICE ANALYSIS» . All documents are the part of the design project documentation. According to API Section 17.5.3, part 1, the assessment for seismic loading is not required for seismic zones 0, 1 and 2 due to, as specified in part 4 of same API Section, there was no significant level ground motions during platform exploitation. According to the technical documentation of the platforms IKA A « DESIGN PREMISES FOR JACKET & DECK STRUCTURES» and IKA B « DESIGN PREMISES FOR MONOPOD & DECK STRUCTURES» the design value of maximum ground acceleration of the field of platforms IKA A, B and IVANA C is set to value for the period of 200 years and for the period of 2000 years. For the platform IVANA C according to the document « MONOPOD AND DECK – DYNAMIC AND SEISMIC ANALYSIS» , the design value of maximum ground acceleration is set to value for the period of 200 years and for the period of 2000 years. According to API Sections 17.5.3 and C2.3.6.c platforms IKA A, B and IVANA C are inside seismic zone 2 where seismic loading is not a requirement in design level analysis if there was no significant seismic changes during exploitation. Procedure of survey of structural elements and criteria for their selection are transferred from ISO standards and API recommendations. Conclusions are supported by newest cognitions of the assessment of the offshore gas and oil platforms from the MMS workshop held on September 2003 in New Orleans. Minerals Management Service (MMS) is a bureau of U.S. Department of Interior, which ensures the safety and integrity of the existing structures, among others oil and gas platforms. The procedure of platforms assessment is described in this elaboration, including the selection of structural elements according to the defined criteria. Elements of platforms that need to be surveyed are sorted in tables in the groups of medium and low risk. Volume of elaboration is 51 pages, contents of seven sections, 37 figures and 5 tables, and referring to 27 papers and documents. Postulates that need to be emphasized are underlined due to better orientation in text. Annex of elaboration consists of all groups of elements and their properties listed from the design project documentation for the platforms IKA A, B and IVANA C.

offshore gas platform; survey; risk assessment; structural elements

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