Answer
The International Association of Classification Societies (IACS) Common Structural Rules are a unified set of engineering standards applied to the structural design and building of specific ship types.
Key Objectives
To eliminate competition between classification societies regarding structural safety standards.
To ensure that a vessel built under any IACS member society has the same minimum baseline of hull structural strength, ultimate strength capability, and fatigue life
Applicability
The CSR applies specifically to:
Double Hull Oil Tankers: Length (LLL) greater than or equal to 150 meters
Bulk Carriers: Length (LLL) greater than or equal to 90 meters (including ore carriers, but excluding combination carriers).
Structural Aspects Governed by CSR
Scantling Requirements: Minimum thickness criteria for keel, bottom shell, side shell, deck plating, and bulkheads to withstand local and global loads.
Load Assessment: Considers both static loads (cargo weight, buoyancy) and dynamic wave loads (slimming, pitching, rolling) over a standard 25-year design life in North Atlantic wave environments.
Ultimate Strength: Assesses the hull girder's ultimate capacity to resist catastrophic buckling or bending failure under extreme conditions.
Fatigue Life Assessment: Mandatory fatigue strength checks for structural details prone to cyclic stress concentrations (e.g., inner bottom connections, hopper tank knuckles).
Corrosion Waste Margins: CSR utilizes a "Net Scantling Approach." Structural strength calculations are done using the net thickness (original thickness minus a designated corrosion addition). The steel must remain strong enough even after 25 years of expected rust degradation.