IACS UR S11

IACS UR S11 is the unified requirement for longitudinal strength of the hull girder, applying to steel ships over 90 m in length. It sets the design vertical bending moment as the still-water component from the loading manual plus a rule wave component, M_w = C1 * C2 * L^2 * B * (Cb + 0.7) in kN m with C1 a length-dependent coefficient and C2 a sagging or hogging factor. From this it fixes the minimum midship section modulus, a minimum moment of inertia, and the permissible hull-girder stress. The companion UR S11A, in force from 2016 after the MOL Comfort loss, adds harmonized buckling, an ultimate hull-girder capacity check, and whipping for container ships.