Influence of the cross section shape on the behaviour of SRG-confined prismatic concrete specimens

The effectiveness of the steel-reinforced grout (SRG) jacketing technique in increasing both strength and deformation capacity has been substantiated by experimental evidence (Thermou and Pantazopoulou in Fib Struct Concr J 8: 35-46, 2007; Thermou et al. in ECCOMAS Thematic Conference, 2013; Thermou et al. in Mater Struct J, 2013). What it has not been addressed yet is the influence of the cross section shape on the behaviour of SRG-confined prismatic unreinforced concrete specimens. An experimental study was carried out where 18 concrete small scale specimens were tested to failure under concentric uniaxial compression load. A single layer of the steel-reinforced fabric was applied to circular, square and square specimens with rounded edges. Test results demonstrated that both strength and deformation capacity increased as the shape of the cross section changed from square to circular. In case of the square specimens, the gain in compressive strength was satisfying, whereas the ductility increase was more significant compared to that of the square specimens with rounded edges. An analytical expression for the lateral confining pressure exerted by the composite system was derived based on the assumption that the steel cords were treated as well-anchored steel stirrups placed at a distance equal to the spacing between the steel cords. The ability of the various steel and fiber-reinforced polymer confinement models from literature to predict the normalized compressive strength of non-circular specimens confined with SRG jackets was also explored.