Analysis on axial compressive performance of embedded circular steel tube totally-recycle concrete composite columns

To study axial compression performance of embedded circular steel tube totally-recycle concrete composite columns, five composite column specimens and three contrast specimens were tested. Through this test, the combination effect of embedded circular steel tube is mainly discussed, and the influence of stirrup ratio and steel tube area ratio on bearing capacity, ductility and damage properties was also analyzed. Test results show that the peak load of totally-recycle concrete filled steel tube column is far behind the hollow reinforced concrete column. In other words, concrete filled steel tube in the core of composite columns gradually works after the outer concrete reaches the bearing capacity. With the increasing of stirrup ratio, the bearing capacity and ductility of the composite columns has a growth trend, and the cumulative damage slows. When the steel tube area ratio is increased, the bearing capacity decreases and the ductility improves, and the damage occures earlier but develops slowly in the late loading. The results calculated by technical specification for steel tube-reinforced concrete column structure (CECS 188:2005) are in good agreement with test results, indicating that the axial compression bearing capacity of embedded circular steel tube totally-recycle concrete composite columns can be designed with CECS 188:2005.