Plate Panel (Rectangular)
A plating bay under uniform pressure — hull and deck plating between stiffeners, a tank top, a bulkhead, a cover. Deflection is α·p·b⁴/D and bending stress β·p·b²/t², where b is the SHORT side and D = Et³/(12(1−ν²)). The short side is what matters: halving the stiffener spacing quarters the stress.
The coefficients are computed from plate theory rather than copied from a table — the exact series solution for simply supported edges, and an energy solution for clamped. Plating welded to stiffeners sits between the two: clamped is the honest case for stress at the weld, simply supported the safe bound for deflection. Once the plate is settled, the stiffener under it carries the same pressure to the frames.
Calculator
Small-deflection plate theory for a uniform pressure on one bay, isotropic material, edges that do not pull in. It is not a class-rule scantling check: a rule thickness carries corrosion and minimum-thickness rules and its own pressure head on top of this. A helper, not a substitute for engineering judgment.