Behavior of square fiber reinforced polymer–high-strength concrete–steel double-skin tubular columns under combined axial compression and reversed-cyclic lateral loading

•Six square FRP–HSC–steel DSTCs are tested under axial and cyclic lateral loading.•Effects of axial load, column aspect ratio, steel tube size and concrete fill are studied.•Square DSTCs exhibit ductile behavior under combined axial compression and cyclic lateral load.•An increase in axial load and a decrease in aspect ratio result in a decrease in the lateral drift capacity.•Concrete-filling the inner steel tube leads to a significant increase in the lateral drift capacity.

This paper presents an experimental study on seismic behavior of square fiber reinforced polymer (FRP)–concrete–steel columns. Six hybrid double-skin tubular columns (DSTCs) manufactured using high-strength concrete (HSC) were tested under combined axial compression and reversed-cyclic lateral loading. The main parameters under investigation were the axial load level, size of inner steel tube, provision (or absence) of a concrete-filling inside the steel tube, and the column aspect ratio. The results indicate that, in general, square DSTCs exhibit very ductile behavior under combined axial compression and reversed-cyclic lateral loading. However, the important influence of the axial load level on the column behavior is evident, with an increase in the load level leading to a significant decrease in the lateral deformation capacity of DSTCs. The results also indicate that a DSTC with a larger inner steel tube exhibits lower lateral displacement capacity than that of a companion DSTC with a smaller inner steel tube. It is shown, however, that provision of a concrete-filling inside the inner steel tube leads to a significant increase in the lateral deformation capacity of a DSTC with a larger inner steel tube to a level that is higher than that seen in a companion DSTC with a smaller hollow inner steel tube. Experimental results are presented together with accompanying discussions on the influence of the investigated parameters on the seismic behavior of square DSTCs.