Experimental Evaluation of FRP Composite Systems for Confinement of Axially Loaded Unreinforced Concrete Cylinders

The strength and ductility of confined concrete has been proven to far exceed that of unconfined concrete. Confined concrete is achieved by implementing means that would provide lateral pressure exerted on the concrete core in order to increase load carrying capacity and ductility. Over the years, several techniques have been developed to provide confinement for reinforced concrete (RC) axial members in the form of RC, steel and polymeric composite external jackets. This paper presents a summary of results of a multi-phase study that aims at assessing structural behavior of RC short columns confined with either E-glass/epoxy and carbon/epoxy fiber reinforced polymer (FRP) composite jackets with different thicknesses. All tests were based upon procedures of the International Code Council Evaluation Services (ICC-ES) Acceptance Criteria for Concrete and Reinforced and Unreinforced Masonry Strengthening Using Fiber Reinforced Composite Systems (AC125). The FRP composite materials used in this evaluation conform to the ICC-ES AC-85 acceptance criteria. Displacement, strains and loads were continuously monitored and recorded using a calibrated data acquisition system throughout the tests. A summary of different semi-empirical models to predict mechanical behavior of confined columns is presented with a focus on Marwan et al. universal model. A discussion on the performance of each group is presented.