The Effect of Transverse Steel and FRP Jacket Confinement on Mechanical Properties of Concrete Cylinders: an Experimental Study

A. R. Khaloo, Yousef Javid and Horr Khosravi

Department of Civil Engineering, Sharif University of Technology, Tehran, Iran.


This paper presents the results of an experimental study on the behavior of concrete cylinders externally wrapped with fiber-reinforced polymer (FRP) composites and internally reinforced with steel spirals. The experimental work was performed by testing 30 concrete cylinders (120 × 400mm2) subjected to pure compression to achieve the complete stress-strain curve. Test specimens were confined with various internal and external confinement ratios and different types of confining material such as steel, Carbon FRP (CFRP) and Glass FRP (GFRP). The compressive strength, corresponding strain and the complete stress-strain curve of the tested specimenswere indicated. The test results showthat the effect of combined external and internal confinement by FRPs and spirals is different from each of them, separately. In the end, an empirical model for compressive strength of confined concrete cylinders was proposed.

Keywords: Confined concrete, FRP jacket, Steel spiral, Internal confinement, External confinement, Concrete cylinder, Constitutive model.

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