Why Are The Surfaces Of Containers Uneven?

In container terminals or certain games, we often find that the sides of containers are often uneven. What is the significance of this special structure?
This type of concave convex structure is called a groove shaped bulkhead in engineering. The cross-sectional shape of the groove shaped bulkhead is shown in the figure, including triangles, rectangles, trapezoids, arcs, etc. Among them, trapezoidal profiles are more widely used.
The groove shaped bulkhead is made of steel plates, and its groove shaped bending replaces the role of reinforcing materials (steel hull structural materials added to ensure the rigidity of the metal plates). Compared to flat bulkheads, slotted bulkheads have the advantage of reducing structural weight and saving steel while ensuring the same strength conditions. Meanwhile, due to the cancellation of reinforcing materials and their brackets, the workload of assembly and welding has been reduced. On bulk carriers and oil tankers, it is more convenient to clear the cargo hold, which is beneficial for preventing rust. However, the groove shaped bulkhead also has some drawbacks, mainly due to its poor pressure bearing capacity perpendicular to the groove direction; In addition, to ensure the strength of the groove shaped bulkheads, it is necessary to make the groove shape have a certain depth and occupy a larger tank capacity, which is not very beneficial for the tank capacity of general cargo ships, but has no impact on bulk carriers and oil tankers. Therefore, groove shaped bulkheads are mostly used in bulk carriers and oil tankers.