Steel tube filled with recycled concrete incorporating steel-fiber reinforcement and self-stressing effect

Abstract

To widespread use of construction and demolition waste (CDW), an innovative steel-fiber-reinforced self-stressing recycled aggregate concrete filled steel tube (SFRCFST) is put forward. The mechanical behavior of SFRCFST under compression-bending is explored in this study. 27 specimens are conducted under eccentric compressive load, and the considered parameters are eccentricity ratio, steel tube thickness, concrete strength grade, quality replacement rates of recycled aggregate, steel fibers content and self-stress. Test results reveal that eccentric loaded SFRCFST fails in the same way of ordinary CFST columns. As the eccentric ratio is increased, the adverse impact of alternative recycled aggregates is more distinct. A double-reduction of load (Nu) and moment bearing capacities (Mu) of the specimens is observed when recycled aggregate replacement rate is increased. Introducing self-stress improves Nu and Mu with the average amount of 14.90% and 10.55%, respectively. Moreover, the flexural rigidity of SFRCFST columns is also enhanced. Moderate amount steel fibers with volume content of 1.2% ∼ 1.8% bring the improvement of Nu and Mu, as well as greater plastic development potential of SFRCFST columns. A refined FE model is proposed to simulate the eccentric loaded behavior of SFRCFST columns. Numerical results show that self-stress contributes to the confining effect throughout the loading process.