Editing Hollow structural section (section)

==Filled HSS==
HSS is often filled with concrete to improve fire rating, as well as robustness. When this is done, the product is referred to as a ''[[Lally column]]'' after its inventor John Lally of Waltham, Massachusetts. (The pronunciation is often corrupted to ''lolly column''.) For example, barriers around parking areas ([[bollard]]s) made of HSS are often filled, to at least bumper height, with concrete. This is an inexpensive (when replacement costs are factored in) way of adding compressive strength to the bollard, which can help prevent unsightly local denting, though it does not generally significantly increase the overall structural properties of the bollard.