Defining the appropriate level of ductility in a concrete column may depend on the importance of the structure or
the level of earthquake risk in a particular area. The design of lateral reinforcement in a column has to be based
on three criteria:
• To prevent longitudinal steel from buckling: The strain at which buckling of longitudinal steel occurs is
independent of the compressive strength of concrete. Therefore, the spacing requirements suggested for NSC
are applicable to HSC columns.
• To prevent fracture of lateral steel: Using an energy balance method it was shown that increasing
compressive strengths from 50 to 80MPa causes only a small reduction in the hoop fracture strain [Kovacic,
1995].
• To provide adequate confinement for ductility: A formula was proposed by Mendis & Kovacic [1999] to
calculate the spacing of lateral reinforcement by modifying the present requirements in AS3600 [1994]. In
the method suggested in the paper, adequate ductility is provided for a high strength concrete column by
comparing its moment-curvature characteristics with that of a normal strength concrete column. The level of
ductility obtained from a 50MPa concrete column is therefore also ensured for the same column made with
high strength concrete. Limits are also determined for the longitudinal steel buckling and lateral steel
fracture