Study Of Recycled Aggregate Concrete-Filled Steel Tube Column On Menchanical Properties After High Temperature

Recycled aggregate concrete filled steel tubular as a new green combined structural system, can fully utilize construction waste, effectively reduce energy consumption and be environmentally friendly. This new technique includes the advantages of aggregate concrete filled steel tubular’s high bearing capacity and ductility, and thus, such technology can be widely applied in the future. There are researches studied on concrete confined steel tube under axial compression and seismic resistance, and this paper focus on the capacity of axial compression and seismic resistance performance of recycled aggregate concrete filled steel tubular under high temperature in order to provide more information for further studies.By using the parameters, such as replacement rate, temperature, confinement index and cooling mode, and by conducting axial compression experiments for 44 recycled aggregate concrete short columns filled steel tubular, this paper acquired various axial compression performance index, such as stress-strain curve, peak stress, peak strain, ductility and stiffness degradation, etc. The experiment results showed that temperature substantially influences bearing capacity and ductility of the specimens and replacement rate has greater impact on ductility and stiffness than bearing capacity; while cooling mode has less impact on bearing capacity but largely influences on ductility and stiffness; the large value of confinement index shows that the concrete has large bearing capacity, leading to backwards movement of overall peak strain point because the steel tubular has better constrain effect on concrete. In this case, regulation AIJ(1997) or Han Linhai formula is suggested to calculate ultimate bearing capacity of axial compaction of recycled aggregate concrete filled steel tubular under high temperature.By using the parameters, such as replacement rate, temperature, confinement index and cooling mode, and by conducting low cyclic loading experiments for 8 recycled aggregate concrete short columns filled steel tubular, this paper acquired seismic resistance performance index, such as hysteretic curve, skeleton curve, feature point and stiffness degradation performance, energy consumption and stiffness degradation, etc. The experiment results showed that the shape of specimens hysteretic curves are plumping and the average ductility index for the specimens is between 2.82 and 5.47 with the average value of 3.56 showing the good ductility performance of the specimens; the equivalent viscous damping coefficient of all specimens at failure moment is between 0.4122 and 0.5377 which is more than 2 times of normal reinforced concrete structure, showing that all the specimens are still in good performance in energy consumption under low cyclic loading and high temperature; replacement rate influences less on feature point load and cooling mode also has less impact on ultimate bearing capacity, while temperature has adverse effects on bearing capacity but increasing section area can increase bearing capacity of specimens in great deal; with the increment of confinement index leading to the decreasing stiffness degradation, initial stiffness of specimens decrease as the temperature increase, Meanwhile, cooling mode has great impact on initial stiffness but less on maximum stiffness degradation. Using CECS regulation to calculate the horizontal bearing capacity of recycled aggregate concrete filled steel tubular under high temperature is possible.