ISO 19901-3:2014 gives requirements for the design, fabrication, installation, modification and structural integrity management for the topsides structure for an oil and gas platform. It complements ISO 19902, ISO 19903, ISO 19904‑1, ISO 19905‑1 and ISO 19906, which give requirements for various forms of support structure. Requirements in this part of ISO 19901 concerning modifications and maintenance relate only to those aspects that are of direct relevance to the structural integrity of the topsides structure.
ISO 19901-3:2014 is applicable to the topsides of offshore structures for the petroleum and natural gas industries, as follows:

topsides of fixed offshore structures
discrete structural units placed on the hull structures of floating offshore structures and mobile offshore units
certain aspects of the topsides of arctic structures.

ISO 19901-3:2014 contains requirements for, and guidance and information on, the following aspects of topsides structures:

design, fabrication, installation and modification
in-service inspection and structural integrity management
assessment of existing topsides structures
reuse
decommissioning, removal and disposal
prevention, control and assessment of fire, explosions and other accidental events.

ISO 19901-3:2014 applies to structural components including the following:

primary and secondary structure in decks, module support frames and modules
flare structures
crane pedestal and other crane support arrangements
helicopter landing decks (helidecks)
permanent bridges between separate offshore structures
masts, towers and booms on offshore structures.