Ductility assessment of two-chord composite steel-concrete battened columns

The ductility of a column is one of the most important characteristics of a structure subjected to unexpected overloads, load reversals, blast loads or dynamic impacts. Structural ductile members are capable of dissipating large amounts of energy by undergoing large deformations before failure, hence providing early warning to the occupants of the building. Previous analyses conducted by the authors suggest that, in addition to the type of column (steel, reinforced concrete and composite steel–concrete), the applied measure of ductility as well as other factors (the materials used and the loading and boundary conditions) have a significant influence on a column’s ductility. This paper proposes a new approach to the analysis of the ductility of columns. This approach distinguishes between the column’s pre-peak, post-peak and total ductility, and develops ductility parameters based on the displacement and energy for each of these ductility types. Based on experimental and numerical research on two-chord composite steel–concrete columns subjected to vertical monotonic loads, the influence of concrete strength and batten plate spacing on the columns’ vertical ductility is evaluated. It is concluded that designing two-chord composite steel–concrete columns to have small batten plate spacing and a relatively low concrete strength class can maximise the vertical ductility.