For larger planters that address 50" or wider (depending on the design), will need to have small structural changes to make the planter stronger, more durable and long lasting.
Hat Bracing is used on the lengths of the planter. A bar that looks somewhat like a top hat, is placed on the lengths of the planter and is welded together.
A top lip allows the top area of the planter to stay strong and holds the walls together. On top of having a lip, you can also request to have a return. A return is a 90degree lip to the already existing top lip. The width of the top lip and return are normally 1-2".
What goes into the planter
If the plants that are going into that planter don't need too much soil, you may use a void filler. A void filler basically uses another material to fill up space. This material is normally a light weight, sponge-like foam. This will keep the weight lighter and makes the walls of the planter have less stress.
These are only a few things to consider when you are buying an aluminium planter.