In THE STRUCTURAL ENGINEER (July, 1948) Hajnal-Konyi described tests on concrete columns reinforced with square twisted steel (T.S.) and mild steel (M.S.) The tests showed that columns with T.S. have substantially higher failure loads than those with M.S. and may undergo large deformations before collapsing. Adequate warning of failure is given by gradual cracking of the concrete whereas normal tied columns reinforced with M.S. often exhibit a brittle failure, which is undesirable in any structure.
Professor R. H. Evans and K. T. Lawson