This ÖNORM EN ISO gives requirements for the design, fabrication, inspection, modifications and structural integrity maintenance of the topsides structure for an oil and gas production platform. It complements ISO 19902, ISO 19903, ISO 19904, ISO 19905 and ISO 19906, which give requirements for various forms of supporting substructure. Requirements in this document concerning modification sand maintenance relate only to those aspects that are of direct relevance to the structural integrity of the topsides structure.