When designing a ship's structure, what are the minimum size and thickness requirements for structural parts, as specified by classification societies, commonly called?

The minimum size and thickness requirements for structural parts of a ship, as specified by classification societies, are commonly called scantlings. Scantlings refer to the precise dimensions, such as thickness, depth, and sectional properties, of all structural components that form the ship's hull. These components include the plating that forms the shell, decks, and bulkheads, as well as reinforcing members like frames (transverse supports for plating), stiffeners (longitudinal or transverse members that increase plating rigidity), girders (large longitudinal supports), and beams (transverse supports for decks). Classification societies are independent, non-governmental organizations that develop and publish detailed technical rules, known as 'Rules for the Classification of Ships', which govern the design, construction, and maintenance of vessels. Their primary purpose is to ensure the structural integrity, safety, and reliability of ships, thereby protecting human life, property, and the marine environment. The determination of scantlings involves complex engineering calculations that consider all anticipated loads a ship will experience throughout its operational life. These loads include static forces from the ship's weight, cargo, and buoyancy (known as still water loads), dynamic forces from waves such as hogging (when the ship bends upwards in the middle) and sagging (when the ship bends downwards in the middle), and localized forces from impacts, pressure, or concentrated weights. The scantlings are carefully specified to ensure that the stresses generated by these loads remain within acceptable limits, providing a sufficient margin of safety against structural failures like yielding (permanent deformation), buckling (sudden loss of stability in compression), and fatigue (failure due to repeated stress cycles). Adherence to these scantling requirements is mandatory for a ship to receive and maintain its class certificate, which is essential for operation and insurance.