engleski

Interpretation of Results of Evaluation and Selection of Structural Elements for Survey of Annamaria A Platform

Modern methods and techniques in solid mechanics are able to obtain reliable information on the state of stresses and strains of any kind of structure. Comprehensive assessment of the real loading and boundary conditions with regard to time-depending effects on the material response like fatigue, ageing as well as physical/chemical deteriorations on existing structure is obviously the task of total exploiting and utilization of inherent potentials. 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. The ability to detect changes in a structure in order to improve its reliability s going to be provide through periodical structural health monitoring. Scheduled manual inspections based on non-invasive damage detection techniques are used to continuously monitor components and, if necessary, to confirm decision for component repair and replacement. The Annamaria A Platform is installed in the Annamaria Field located in the Croatian offshore of the Central Adriatic Sea in a water depth of 57 m. The platform is designed as manned platform. According to the task defined for the offshore platforms, 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 project documents and calculations for the platform ANNAMARIA A PLATFORM «TECHNICAL REPORT FOR JACKET IN SERVICE ANALYSIS» and «TECHNICAL REPORT FOR DECK STRUCTURAL IN SERVICE ANALYSIS» have been used. 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. Platform ANNAMARIA A is 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 higher and low risk. Properties of particular elements and their global coordinates are not available in project documentation for platform ANNAMARIA A, while their position is clearly determined in schematic layout of elements. Volume of elaboration is 37 pages, contents of seven sections, 27 figures and 2 tables, and referring to 22 papers and documents. Postulates that need to be emphasized are underlined due to better orientation in text.

offshore gas platform; survey; risk assessment; structural elements

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