Experimental Research And Numerical Simulation On Recycled Aggregate Concrete-filled Square Steel Tubular Long Columns Under Axial Compression

Recycled concrete filled steel tube structure is a new type of composite structure which was poured recycled concrete into the steel tube. The restriction of steel tubes improves the mechanical properties of core recycled concrete. At the same time, as the protection of steel tubes, the durability of recycled concrete gets improved.To recycled aggregate concrete-filled square steel tubular long columns under axial compression, this paper does experimental studies and ANSYS finite element analysis, investigates the mechanical properties of recycled aggregate concrete-filled square steel tubular long columns under axial compression. Varying with recycled aggregate replacement rate, thickness of steel pipe and slenderness ratio,3 groups which totalled 7 pieces recycled aggregate concrete-filled square steel tubular long columns were made and tested under axial compression. This paper researched the performance indexes of axial compression, such as ultimate axial bearing capacity, average strain under the ultimate bearing capacity and elastic stiffness. Based on the tests, try using ANSYS finite element analysis to simulate the axial compression tests of recycled aggregate concrete-filled square steel tubular long columns, explore using ANSYS analysis to assist and even replace axial compression tests.The results of experimental studies and ANSYS finite element analysis show that:(1) Aspect of axial compression failure pattern:with the change of the recycled aggregate replacement rate, the failure pattern of recycled aggregate concrete-filled steel tubular long columns under axial compression has no significant effect. The same as common concrete-filled steel tubular long columns, with the increase of slenderness ratio and thickness of steel pipe, the failure pattern of specimens tends to global instability.(2) Aspect of axial compression bearing capacity:with the increase of aggregate replacement rate, the axial compression bearing capacities of recycled aggregate concrete-filled steel tubular long columns go down slightly, but not remarkably. They are almost equal. The same to common concrete-filled steel tubular long columns, with the decrease of slenderness ratio and the increases of thickness of steel pipe, the bearing capacities of specimens increase significantly. The two calculated values of axial bearing capacities of recycled aggregate concrete-filled square steel tubular long columns, using CECS 159:2004 and GB 50936-2014, both have good consistency with the test values.(3) The ANSYS finite element simulation method explored agrees well with the experiment. It has high reliability and can assist, even replace the axial compression tests of recycled aggregate concrete-filled square steel tubular long columns very well.