Ductility of slender reinforced concrete columns under monotonic flexure and constant axial load

In this paper an investigation is presented based on tests results of reinforced concrete columns subjected to monotonic flexure and constant axial load from a previous paper [1]. The variables of the tests were strength of concrete (30, 60 and 90 MPa), shear span ratio (M/(V · h) = 7.5, 10.5 and 15), axial load level (0–45%), and transversal and longitudinal reinforcement ratio (1.4–3.2%). This paper is a continuation of the aforementioned but focuses on the deformation capacity, which depends on the method selected to idealize the response diagram comparing four of these methods. The results show that the parameters affecting ductility are greatly influenced by the different methods. It was observed that the ductility in displacements does not always decrease with axial load and column slenderness. In addition, a new equation is proposed to obtain the ultimate displacement for slender columns.

► Ductility in curvatures decreases with the strength of concrete, the cover and the reinforcement ratio.
► Ductility in displacements does not always decreases with the axial load and the slenderness.
► A new equation is proposed to obtain the ultimate displacement for slender columns.
► The plastic hinge length increases with the axial load, slenderness and the reinforcement ratio.