Seismic behavior of full-scale square high-strength RACFST columns

Abstract

The research purpose was to investigate the seismic behavior of full-scale square high-strength recycled aggregate concrete-filled steel tube (RACFST) columns. With the recycled coarse aggregate (RCA) replacement ratio, shear-span ratio and axial compression ratio as the variation parameters, seven column specimens were subjected to low-frequency cyclic loading tests. The test results showed that square high-strength RACFST columns had reliable seismic performance, their failure modes were similar to those of normal CFST columns, and the damage was mainly concentrated at the column roots. The bearing capacity and ductility of high-strength RACFST columns were less affected by the RCA replacement ratio, while the shear-span ratio and axial compression ratio had a greater impact on the peak bearing capacity, ductility, and other hysteretic behavior indexes. Meanwhile, a restoring force model established based on the test research and theoretical analysis agreed well with the test hysteresis curves. Finally, a fiber element model (FEM) using Opensees software was developed and a good agreement was achieved between the test and predicated results. The so-validated numerical model was then used to investigate the influence of the key parameters, such as the RCA replacement ratio, diameter-to-thickness ratio, axial compression ratio, shear-span ratio, and steel yield strength on the seismic performance of square high-strength RACFST columns.