Experimental investigation on eccentric compression behavior of FRP-confined concrete-encased cross-shaped steel columns

FRP-confined concrete-encased cross-shaped steel column (FCCSC), composed of an outer square glass-fiber -reinforced plastic (GFRP) tube, the internal cross-shaped steel, and the filled concrete, is a novel type of com-posite column. Eleven square FCCSCs were tested subject to eccentric axial compression load. The influence of eccentricity and slenderness ratio was evaluated and investigated. The test results showed that both the axial load-bearing capacity and lateral confinement efficiency of FRP tube reduced with the increase of eccentricity and slenderness ratio. The maximum reduction in axial load-bearing capacity was up to 50.7 % and 71.1 %, with the eccentricity varying from 0 mm to 50 mm and 100 mm, while the maximum reduction was about 18.1 % and 27.5 % when slenderness ratios increased from 10.44 to 20.87 and 34.79, respectively. The ductility of eccentric compressed FCCSCs can be evaluated by combined strain. It is indicated that short columns exhibited the best ductility, and the ductility increased with the increase of eccentricity. However, the ductility of slender columns reduced with the increase of eccentricity. Based on the test results, the experimental axial force (N)-moment (M) interaction curve of FCCSCs was obtained, and the balanced failure between compression and tension failure mode was recommended.