STUDY OF ULTIMATE BEARING CAPACITY OF RECYCLED AGGREGATE CONCRETE-FILLED CIRCLE STEEL TUBE SHORT COLUMNS UNDER AXIAL COMPRESSION AFTER HIGH TEMPERATURE

ZTo study the mechanical behavior and ultimate bearing capacity of recycled aggregate concrete-filled circle steel tube short columns under axial compression after high temperature，20 recycled aggregate concrete-filled circular steel tubular short columns specimens were designed and tested，and three varying parameters were considered in the test，which were recycled coarse aggregate replacement percentage，constant temperature and constant temperature time． The influences of different parameters on ultimate bearing capacity of specimens were analyzed． Unified strengthen theory and superposition calculation theory were used to calculate the ultimate bearing capacity of specimens，whose results were compared with the test results． The results of study showed that the failure process and form of recycled aggregate concretefilled circular steel tubular columns under axial compression after high temperature were similar to ordinary concrete-filled steel tube columns． Constant temperature had significant effect on the bearing behavior． Bearing capacity with the extension of constant temperature time showed a trend of first increase and then decrease at the same temperature; aggregate replacement had little effect on bearing capacity; the unified strengthen theory calculation formulas proposed by Zhong Shantong was used to calculate ultimate bearing capacity of recycled aggregate concrete-filled circular steel tubular short columns after high temperature， the calculated results agreed well with the test results．