Direct calculation method

The direct calculation method is a strength assessment that solves the structural response of a ship by finite element analysis instead of relying only on prescriptive scantling formulas. Class rules set design load cases (still-water and wave bending, external sea pressure, internal cargo and ballast loads), and the analyst builds a three-dimensional FE model of a cargo-hold or full-ship block to check stress, buckling, and fatigue against rule acceptance criteria. The harmonized IACS Common Structural Rules for bulk carriers and oil tankers require direct strength analysis for primary supporting members alongside prescriptive checks. It catches stress concentrations at brackets and openings that closed-form rules cannot resolve.