Sagging

Longitudinal hull-girder bending in which the midship is unsupported in a wave trough while the bow and stern ride on adjacent crests, putting the strength deck into compression and the bottom into tension. Sagging combines with still-water sagging from light-amidships, heavy-end loading conditions; class still-water bending moment limits in the loading manual must be observed at every cargo and ballast stage. Persistent sagging accelerates fatigue at deck strakes, hatch corners and longitudinal-to-transverse intersections, all primary surveyable items under IACS Common Structural Rules.