Experimental Study On Seismic Performance Of Recycled Aggregate Concrete Columns

The technology of recycled concrete achieves the recycling use of waste concrete, which has good social and economic benefits and is an important part of sustainable development of construction industry. Columns are the main vertical bearing component of reinforced concrete structure, so to strengthen the research on the seismic performance of recycled concrete column has important guiding significance to the popularization and application of recycled concrete in practical engineering.This paper makes recycled coarse aggregate replacement ratio(0, 50%, 100%), axial compression ratio(0.15, 0.30, 0.45) and stirrup volume rate(1.64%, 1.09%, 0.66%) as control variables, and nine recycled concrete columns whose shear span ratio are 4.2 have been designed and produced. Systematically investigate the seismic performance of recycled concrete columns, and the specific work are as follows:(1) Nine columns have been tested under low cyclic load, meanwhile observe and record the damage phenomena of each specimen. The failure models of the recycled concrete columns and ordinary concrete columns are comparatively analyzed. The results show that the failure modes of the specimens is given priority to bending failure and it will tend to be bending-shear failure as high axial compression ratio.(2) Analyze the load-displacement hysteresis curves of all the specimens and discuss the relation between indexes of skeleton curve, ductility, rigidity degeneration and energy dissipation and recycled coarse aggregate replacement ratio, axial compression ratio and stirrup volume ratio. The results show that ductility of the column is best when the replacement rate is 50%, but the bearing capacity will gradually reduce with the increase of replacement ratio; as the axial compression ratio increases, the bearing capacity is higher, but the ductility worse, the rigidity degradation faster; the volume stirrup ratio has little effect on bearing capacity, rigidity degradation and energy dissipation of specimens, but the increase of the volume stirrup ratio leads to the increase of displacement ductility.(3) Observe the development of longitudinal reinforcement and stirrup strain of specimens, and the flexural deformation, shear deformation and slippage of longitudinal reinforcement of the plastic hinge area are measured separately, then analyze the contribution and changing rules of these three kinds of deformation and the relation between total deformation of the plastic hinge area and displacement on the lateral vertex. The result shows that the longitudinal reinforcement strain and stirrup strain are restricted as stirrup volume rate increases. The specimens are given priority to flexural deformation, and slippage of longitudinal in the plastic hinge bar area increases with the increase of recycled coarse aggregate content; deformation of plastic hinge area accounts for over 80% of the displacement on the lateral vertex.(4) According to the compressive strength of concrete measured by rebound method and ultrasonic-rebound combined method before and after the low cyclic test, evaluate the damaged condition of the concrete outside the plastic hinge area, and provide references for damage assessment and retrofit of the recycled concrete columns after earthquake.