STRENGTH AND DUCTILITY BEHAVIOUR OF CONCRETE COLUMNS UNDER COMPRESSION WITH DOUBLE LAYERED STIRRUPS: AN EXPERIMENTAL STUDY

The strength and ductility of concrete ameliorated by providing appropriate confinement has paved way for designing structures that would withstand loads of extreme intensities. The behaviour of concrete confined by single layered transverse reinforcement has already been construed substantially. This paper presents a consistent experimental study conducted on a novel and recently proposed Reinforced Concrete column consisting of two layers of confining reinforcement. The concrete inside the column experiences three different levels of confinement, viz., doubly confined concrete inside the inner layer of lateral reinforcement, singly confined concrete between the two layers of the transverse reinforcement, and the unconfined concrete cover. The variables contemplated to study the behaviour and amount of confinement in double layered stirrup concrete column comprise: addition of inner layer, variedness in the shape and form of the transverse reinforcement forming the inner layer, grade of concrete, varying number and amount of longitudinal reinforcement forming the outer layer, proximity ratio between the inner and outer layers and the varied amount and spacing of transverse reinforcement encompassing the inner layer. It has been ascertained that the confinement effects emerged from the use of single layered stirrup transverse reinforcement were deficient when compared to that of double layered stirrup transverse reinforcement. Aside from enhanced strength and ductility, this novel structural form of concrete column exhibited an added advantage in terms of ease of construction over conventional single layered stirrup column