Why Longitudinal corrugated bulkhead have horizontal corrugation?

Corrugated Bulkhead

Longitudinal Bulkhead are provided to add longitudinal strength to the ship.

They would be subjected to longitudinal bending (Sagging & Hogging ).

So by putting horizontal corrugation on longitudinal bulkheads we are adding up strength to them to resist bending.

How does it work ?

Second moment of Area also know as second moment of inertia is measure of the “efficiency of cross sectional shape to resist bending caused by loading .

In above figure if you notice, both the beams have the same area and even the same shape . but Beam 1 is stronger than Beam 2 because its second moment of area is high .

Second moment of Area Ic= b(h*h*h)/12 . Hence Since h is greater in case of beam 1 it will be stronger than beam 2 .

Similarly , Longitudinal Bulkheads with horizontal corrugation will have high bending resistance compared to longitudinal bulkheads with vertical corrugation