In order to analyze the control effects of replacement rate of the demolished concrete and steel rate on seismic behavior of demolished concrete composite structures from the structure level

pseudo-static test of frames

which comprise four circular steel tubular columns filled with recycled mixed concrete

subjected to axial load and cyclical horizontal load was conducted.The effects of these two parameters on the seismic behavior indexes including hysteretic performance

skeleton curve

ductility

stiffness degeneration and dissipation were studied.The results show that all the failure modes of four circular steel tubular frames were the breaks of the beam hinge.With the steel column section rate increasing from 3.8%to 7.7%

the horizontal bearing capacity

the plastic deformation capacity and the ductility coefficient of the specimens rise significantly

and the degeneration rate of stiffness reduces.However

the influence rule of the recycled concrete rate on the targets is contrary to that of steel rate and the influence degree is limited.The synergetic action of the demolished concrete rate and the steel rate leads to various horizontal bearing capacities and energy-dissipating capacities of the structures.