Axial Compression Mechanical Properties of ECC-square Steel Tube-recycled Aggregate Concrete Composite Columns and Simplified Calculation Formula of Axial Compression Capacity

To address the issues of durability and poor ductility of square steel pipe (SP)-recycled concrete composite column (RAC-SP-RAC-C), this paper introduces an ECC-square steel tube-recycled concrete composite column (ECC-SP-RAC-C), and investigates the influence of parameters such as width-to-thickness ratio, material strength and recycled aggregate replacement rate on its axial compression mechanical properties through numerical simulation analysis. The findings indicates that the axial compressive load capacity of ECC-SP-RAC-C is calculated by the formula. The finding indicates that ECC-SP-RAC-C is better than RAC-SP-RAC composite columns in terms of ductility, energy dissipation and load carrying capacity. A smaller the width-to-thickness ratio (the thicker the ECC shell) the higher the ductility of the specimens, yet reduces load-bearing capacity and energy dissipation capacity. The increase of steel tube strength or thickness increases the bearing capacity, energy dissipation and ductility of the specimen, but the higher the steel tube strength the smaller the effect of ECC, and the opposite effect of steel tube thickness; the increase of ECC and RAC strength increases the bearing capacity and energy dissipation capacity of the composite column, and the low strength ECC and high strength core RAC exhibits a better combination effect and good ductility; the increase of recycled coarse aggregate replacement rate, the composite column The load bearing capacity decreases and ductility increases. The formula of axial compression load bearing capacity of composite columns exhibits good applicability.