Behavior of concrete columns under the confinement of transverse steel hoops and FRP

Synopsis: FRP is customarily used to wrap concrete columns to increase their strength and strain capacities bj providing extra confinement. Typically, steel hoops or spirals are used in constructed columns as mandated by codes The behavior of retrofitted columns becomes thoroughly different because there are two systems with differen mechanical response and interaction engaged in confinement. While most of the literature addressed concrete confinée with FRP only, a limited number of studies and experimental cases accounted for both actions. This paper developec an axial stress-strain model which utilized geometric and mechanical properties of concrete, steel and FRP. ТЫ proposed work adopted Lam and Teng model for concrete confined with FRP, originally implemented in ACI 440.2R 17 guide, and calibrated its parameters against experimental curves. The proposed model correlates well wit! experimental cases that were collected from the literature.