Why is the surface of the container uneven?

The sides of freight containers or container houses are often uneven. What is the significance of this special structure?

This concave convex structure is called trough bulkhead in engineering. The section shape of trough bulkhead is shown in the figure, including triangle, rectangle, trapezoid, arc, etc. among them, trapezoid section is widely used.

The trough bulkhead is pressed by steel plate, and its trough bending is used to strengthen the role of stiffeners (steel hull structural materials added to ensure the rigidity of metal plate). Compared with plane bulkhead, trough bulkhead has the advantage of reducing structural weight and saving steel under the condition of ensuring the same strength. At the same time, due to the cancellation of stiffeners and their elbow plates, the workload of assembly and welding is reduced. On bulk carriers and oil tankers, it is more convenient to clean the tank and prevent corrosion. However, the trough bulkhead also has some disadvantages, mainly because it has poor bearing capacity perpendicular to the trough direction; In addition, to ensure the strength of the trough bulkhead, it is necessary to make the trough have a certain depth and occupy a large capacity, which is not very beneficial to the capacity of the general cargo ship, but has no impact on the bulk cargo ship and oil tanker. Therefore, trough bulkheads are mostly used for bulk carriers and oil tankers.