Experimental behavior of T-shaped concrete-filled steel tubular columns under diagonal cyclic loading

Abstract

T-shaped concrete-filled steel tubular (CFST) columns have the advantage of avoiding protrusion from walls and can be used as edge columns. The practical structures may be subjected to the earthquake action from different directions, but little attention has been paid to the behavior of T-shaped CFST columns under diagonal cyclic loading. A total of 14 T-shaped CFST columns were tested under constant axial load and lateral cyclic loading. The main variables explored in the test were loading angle, axial load level, concrete compressive strength and section form. The failure mode, lateral load-lateral displacement hysteretic curves, envelope curves, stiffness degradation, ductility, cumulative energy dissipation, deformation and bending moment-curvature curves were investigated. The results show that the hysteretic curves are generally plump and the displacement ductility coefficients are over 3 for the specimens with the axial load levels of less than 0.5. The specimens at 45° and 90° have close envelope curves, while the specimens at 0° exhibit slightly lower lateral ultimate strength and better ductility. The existing codes such as Eurocode 4, AISC 360–10 and DBJ/T 13-51-2010 give obviously higher predictions of initial section flexural stiffness for stiffened specimens without an axial load and conservative predictions for most multi-cell specimens. Furthermore, the existing codes overestimate the serviceability-level section flexural stiffness for most specimens.