Special-shaped partially encased steel–concrete composite (PEC) columns could not only improve the aesthetic effect and room space use efficiency, but also exhibit good mechanical performance under static load when used in multi-story residential and office buildings. However, research on the seismic performance of special-shaped PEC columns is insufficient and urgently needed. To investigate the seismic performance of cross-shaped partially encased steel–concrete composite (CPEC) columns, three CPEC columns were designed and tested under combined constant axial load and lateral cyclic load. The test results show that the CPEC columns had good load capacity and ductility, and that the columns failed because of concrete crushing and steel flange buckling after the yielding of the steel flange. The plump hysteresis loops indicated that the CPEC column also had good energy dissipation capacity. Due to the constraint of hydraulic jacks, increasing the load ratio would decrease the effective length, thereby increasing the load capacity of the CPEC column and decreasing the ductility. A finite element model was also established to simulate the response of the CPEC columns, and the simulated results agree well with the experimental results. Thereafter, an extensive parametric analysis was performed to study the influences of different parameters on the seismic performance of CPEC columns. For the CPEC column with an ideal hinged boundary condition at the top, its lateral load capacity gradually decreases with the growth of the load ratio and link spacing and increases with the rise of the steel yield strength, concrete compressive strength, flange and web thickness, and sectional aspect ratio. This research could provide a basis for future theoretical analyses and engineering application.

A novel CFS composite wall filled with cement-based lightweight polymer material (CFS-CLPM composite wall) has been proposed and proven to have excellent architectural and mechanical performance. To promote its application in prefabricated concrete (PC) frame structures, two full-scale specimens were designed and tested under cyclic loading to investigate the failure mode, hysteretic response and energy dissipation of the PC frame infilled with the CFS-CLPM composite wall. The experimental results indicated that CFS-CLPM composite walls can significantly improve the lateral behavior of the PC frame in terms of load capacity, elastic stiffness and energy dissipation capacity, while slightly reducing its ductility because of the infill-frame interaction. Subsequently, finite element (FE) analyses for the PC frame infilled with CFS-CLPM composite walls were developed and verified against the experimental results. The force-transferring mechanisms between the PC frame and the CFS-CLPM composite walls were revealed by analyzing the stress distributions. The parametric analyses demonstrated that the influential parameters for lateral resistances of the PC frame structure infilled with CFS-CLPM composite walls were the strength of CLPM, the span-to-height ratio and the thickness of CFS-CLPM composite walls. Finally, a formula considering the mechanical contribution of the CFS-CLPM composite wall was proposed to predict the elastic lateral stiffness of the structures. The results of this study could provide a basis for the application of CFS-CLPM composite walls in PC frame structures.