Deck Load Calculator

Deck load capacity is fundamentally a per-square-foot property of the steel structure itself -- plating thickness, the spacing between supporting frames, steel yield strength, and the safety factor you design to -- and this calculator computes it from a simplified fixed-edge plate bending formula before ever multiplying by total deck area. That's why gross deck capacity, expressed in pounds per square foot, does not change no matter how large or small a deck area you enter -- it's a property of the scantlings, not the footprint. Total deck area only comes into play afterward, when converting that per-square-foot capacity into a total load figure in pounds or short tons for a specific deck. Thicker plating and higher steel yield strength both raise the gross capacity, since a thicker or stronger plate resists more bending load before reaching its limit, while wider frame spacing and a larger safety factor both lower it -- wider spacing means each panel of plate spans farther unsupported, and a larger safety factor deliberately derates the raw structural capacity to build in a margin.

Plate self-weight, which is subtracted to get net usable capacity, depends only on plating thickness and steel density, independent of every other input. At sufficiently thin plating with wide frame spacing and a large safety factor, plate self-weight alone can exceed the gross bending capacity -- in that case net capacity is shown as 0 rather than a negative number, with a validity note flagging that the structure cannot carry its own deck plating at those scantlings, let alone any cargo. What this calculator doesn't account for: dynamic and impact loading (a forklift or dropped container loads very differently than a static uniform load), plate buckling under compression, corrosion allowance over the vessel's service life, or welded connection strength at the frame -- all of which a class society's full scantling calculation would need to check separately.