In order to study the mechanical properties of L-shaped columns of recycled aggregate concrete-filled steel tubes (L-RACFST) with a recycled aggregate concrete (RAC) coarse aggregate replacement rate of 100%, three L-RACFST columns with a RAC coarse aggregate replacement rate of 100% were made to carry out axial compression and two-way bias point load tests. The finite element numerical model was verified on the basis of the test. ANSYS was used to investigate the influence of steel strength, steel thickness, width-to-thickness ratio, and eccentricity on the mechanical properties of L-RACFST columns. Results show that: (1) The eccentricity significantly affects the compressive bearing capacity of L-RACFST columns. Compared with the axial compression specimens, the ultimate bearing capacity of the specimens with eccentricities of 40 mm and 80 mm decreases by 18.67% and 24.84%, respectively. (2) An eccentric load will exacerbate the comprehensive bending deformation of the test specimen. (3) During parameter design, eccentricity has a significant effect on the compressive load-bearing capacity of L-RACFST columns with a 100% RAC replacement ratio. However, increasing the steel’s thickness and strength and reducing the width–thickness ratio can effectively compensate for the loss of compression performance caused by eccentricity. The findings of this study provide guidance for the engineering design and application of steel tube RAC composite special-shaped columns with a high replacement rate.

The L-shaped columns of recycled aggregate concrete-filled steel tubes (L-RACFSTs) with a 40% coarse aggregate replacement ratio were selected as the research subject, and axial compression and eccentric compression tests were conducted. Based on validated finite element numerical simulation methods, a parametric analysis was carried out, incorporating key parameters such as steel strength, width-to-thickness ratios of the square steel tube and connecting plate, and load eccentricity. The mechanical properties of L-RACFSTs under axial compression and eccentric compression loads were studied. The results show the following: (1) At a 40% replacement rate, axial compression specimens exhibited obvious in-plane deformation of the column limbs, whereas eccentric compression specimens showed overall bending toward the inner side of the column. (2) As the strength of the steel increases, the axial and eccentric compressive bearing capacities of the specimens gradually increase. It is recommended that structural steel with a strength grade of Q355 is adopted. (3) When the width of a square steel tube is fixed, the axial and eccentric compressive bearing capacities of the test specimen gradually increase as the width-to-thickness ratio decreases. (4) In contrast, for a connecting plate of a fixed width, an increase in the width-to-thickness ratio results in a decrease in bearing capacity. Additionally, due to the increased width of the connecting plate, bearing capacity will decrease in some cases. (5) The bearing capacity under eccentric loading decreases gradually as the eccentricity increases; it is recommended that the eccentricity be kept below 120 mm.