LAUSR

Abstract Four-leggedconcrete-filled steel tube (CFST) latticed members are extensively used as the piers, arch ribs and host towers of bridges. This paper aims to investigate the seismic behaviour of four-legged square CFST latticed members. A total of eight latticed specimens, i.e., six with square CFST chords and circular hollow section (CHS) braces while another two with square hollow section (SHS) chords and CHS braces, were tested under combined axial compression and lateral cyclic loading. The main experimental parameters included: 1) axial compression ratio, from 0.05 to 0.5; and 2) width-to-thickness ratio of the square chord tubes, taken as 55.6 and 28.6. The experimental results clarify that the four-legged square CFST latticed specimens outperform the reference hollow steel ones in terms of hysteretic behaviour. It has also been revealed that, the well-known inward and outward buckling of chord tubes are observed for the hollow steel latticed specimens, whilst for the CFST latticed specimens, outward tube buckling at the bottom of the chords combined with cracking at the front K-shaped chord-brace connections are found to be the main failure patterns. Bearing capacity and ductility index of CFST latticed specimens increase with the decrease of axial compression ratio and chord tube width-to-thickness ratio, and the initial stiffness of CFST latticed specimens also increase with the decrease of the abovementioned two ratios. Finally, a finite element analysis (FEA) model was developed to investigate the hysteretic performance of four-legged square CFST latticed specimens, the feasibility of which was validated by comparison with the experimental results.