Experimental behavior of circular flyash-concrete-filled steel tubular stub columns

The paper presents an experimental study of the structural behavior of circular flyash-concrete-filled steel tubular stub columns under axial compressive loads. In this study, 90% and 100% by weight of the cement in the concrete core was replaced with flyash. Twenty-seven specimens were tested to study the influence of flyash content, wall thickness of the steel tube, and curing age on the ultimate capacity and confinement effect. The experimental results were compared with the design values calculated using AISC-LRFD (1999), ACI (1999), AIJ (1997) and Eurocode 4 (1994). From the experimental study, it was determined that the confinement effect of circular steel tubes filled with high content flyash concrete was better than that of specimens filled with ordinary Portland cement concrete. The 5.88-mm-thick steel tube filled with 100% flyash concrete was equivalent in strength to a steel tube filled with C30 concrete at 28 days.