Hysteretic Behavior Of Recycled Aggregate Concrete Filled Circular Steel Tubular Columns Under Contant Compression And Cyclic Bending

Waste concrete takes the largest proportion (30%~50%) of construction and demoliton waste. Reusing the crushed waste concrete as recycled coarse aggregate (RCA) provides the possibility to produce concrete in an environmentally-friendly way by reducing the consumption of natural resources and saving the landfills for the disposal of concrete waste. Unfortunately, the incorporation of RCA causes decreases in the strength and considerable increases in deformations for the recycled aggregate concrete (RAC). These disadvantages have prohibited the application of RAC in structures. Encasing RAC into steel tube can solve this problem because the mechanical behaviour of RAC will be improved as a result of the confinement effects and sealed environment provided by the outer steel tube. Meanwhile, the buckling of the tube can be delayed due to the exsiting RAC core. Until now, extensive efforts have been dedicated to the static behaviour of the recycled aggregate concrete filled steel tubes (RACFST). However, limited attention has been devoted to the dynamic behaviour of the RACFST columns. In this context, this thesis presents the experimental and numerical analysis on the dynamic responses of RACFST columns under constant axial compression and cyclic horizontal loading.The patent of the rigid beam which is intended to be used cyclically applied in the experiments for the columns under constant axial compression and cyclic horizontal loading has been anaylzed with the commercial finite element software Midas. Based on the analytical results, some improvements were developed for the design of the rigid beam.This rigid beam was applied in the experiment of this thesis.The experiments of the RACFST columns with high strength concrete core under high axial load ratio were carried out to investigate the cyclic behaviour of the specimens. The test set-up consisted of a lateral reaction system supporting the lateral MTS hydraulic actuator and a vertical system supporting two vertical MTS hydraulic actuators. Based on the experimental results of the specimens under different conditions, the recommendations were developed for the experiments which will be conducted in this test set-up.Fiber-based model was developed by numerical programming to analyze the behaviour of RACFST columns under under constant axial compression and cyclic horizontal loading. The reliability of the numerical results was then verified by the avalilabe experimental results in the literatures.An extensive parametric analysis was conducted to investigate the cyclic behaviour of RACFST columns. Considered parameters include the axial load ratio, RCA replacement ratio, compressive strength of concrete core, yield strength of steel tube, thickness of steel tube and slenderness ratio. In addition, the lateral strenghts of the specimens from previous studies preidticed using the existing design provisions from Europe, America, Japan and China for concrete filled steel tubular columns with conventional concrete were compared with the test results.On the basis of the comparisons, design recommendations for RACFST columns under constant axial compression and cyclic horizontal loading have been put forward.