Experimental study of seismic performance of full-scale basalt FRP-recycled aggregate concrete-steel tubular columns

Hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tubular columns (DSTCs) have received extensive attention in the research community over the past decade. Generally, a DSTC consists of an inner steel tube and an outer FRP tube, with the space between them filled with natural aggregate concrete (NAC). This paper studied a new form of hybrid FRP-recycled aggregate concrete (RAC)-steel tubular column (FRSTC) in which the outer FRP tube was made of environmental-friendly basalt fibers and the concrete was made of recycled coarse aggregates (RCAs). Quasi-static tests of five full-scale basalt FRSTCs were conducted to gain an improved understanding of the behavior of FRSTCs, and to enable further application potentiality of FRSTCs in earthquake-prone areas. Three key column parameters, including RCA replacement percentages, axial load ratios, and steel reinforcement ratios were carefully designed to clarify their influence on the performance of FRSTCs under combined axial compression and cyclic lateral loading. The test results, including the hysteretic loops, skeleton curves, curvature and strain distributions, ductility characterization, energy dissipation capacity, stiffness and strength degradation, and cumulative damage, are presented and discussed. The experimental results show that the RCA replacement percentage has little impact on the seismic performance of FRSTCs, while the effect of the axial load ratio is significant. The bearing capacity and energy dissipation of FRSTCs can be superior to those of DSTCs with NAC.