Experimental Study on Cyclic Lateral Loaded Circular CFST Members with Initial Imperfections

To study the influence of an initial imperfection on the cyclic performance of concrete-filled steel tubular (CFST) members, twelve specimens were cast with different notch lengths, notch widths, notch orientations and notch locations. These specimens were implemented in a lateral quasi-static test, and the test details, damage modes, load-deflection responses and strain histories were detailed and recorded. The measured and theoretical equivalent elastic flexural stiffness, displacement ductility coefficient, maximum lateral load, and measured and theoretical bending capacity of all the specimens were collected and analysed. The research results showed that all specimens mainly experienced flexural damage with different damage levels. Good agreement was observed between the measured and theoretical elastic flexural stiffness as well as the bending capacity for the intact specimens (specimen 1 and specimen 2). The mid-span notch weakened the equivalent elastic flexural stiffness, displacement ductility and flexural capacity of the CFST specimens. Furthermore, a horizontal mid-span notch resulted in greater impact on the specimen behaviour than a vertical notch or a quarter-span notch, an observation that deserves particular attention.