A close-range blast event can cause severe damage to building structures due to its ability to produce
very high localised impulsive loads. Such events can result from explosives that are attached to the
critical elements of a structure, backpack and suitcase explosives, and vehicle or parcel bombs
targeting the key structural elements of buildings and bridges. Steel hollow sections are among the
most commonly used prefabricated structural element types that are widely used in Australia.
Therefore, adopting the necessary precautionary measures in the design of such elements against
close-range blast is worthwhile to explore. This paper focuses on an experimental and numerical study
performed on concrete-filled and hollow square tubular columns (100 x 5 mm SHS Grade C350) made
out of cold-formed structural steel hollow sections (SHS) that were subjected to highly explosive TNT
charges. The charges were placed above the top surface of the column at two different scaled standoff
distances of 0.12 m/kg1/3 and 0.15 m/kg1/3. The failure mechanism and the pressure development of
the hollow and concrete-filled columns are discussed and presented. The advantages of using concrete
as an infill material for reducing the structural damage are also discussed.