Floating shelves seem fragile to the common eye because of the means with which they sit on the wall. All the functionings of the brackets are hidden so it seems as though they are floating there on the wall. In reality they are normally much stronger than other types of shelves which are supported with normal brackets and screws.
When designing shelves of this nature, the manufacturers understand that these shelves are hanging with no external support. Therefore, they are specifically designed to be reinforced. This is done by adding attaching screws into the wall and the steel shelf bracket are made from durable materials. They are also extended enough to give great support. With this form of floating shelf support, you are able to position heavy items on these shelves without concern.