Experimental and finite element analysis on the effect of relative eccentricity in double‐C light steel partially encased concrete columns

Load‐bearing capacity and stability of steel members is known to be significantly enhanced by filling concrete into spliced light steel channels. However, strength prediction of such composite columns is quite limited. This study attempts to substantiate and predict the axial and eccentric compressive behavior of a novel double‐C light steel partially encased steel fiber‐reinforced self‐compacting lightweight aggregate concrete column. Experimental investigations were carried out with the relative eccentricity ( e 0 /h ) as the primary variable. The load–axial deformation curves, load–deflection curves, and failure patterns were analyzed to evaluate the combined compression‐bending performance systematically. Finite element (FE) simulations were further employed to investigate the stress distribution of both concrete and light steel skeleton at peak load and the failure stage. The results indicate that the peak load ( N max ) of the axially loaded specimen was 98.4% and 213.3% higher than those of the eccentrically loaded specimens D2 ( e 0 /h = 0.3) and D3 ( e 0 /h = 0.6), respectively. The effective flexural stiffness (EI n ) of specimen D2 exceeded that of D3 by 67.5%. The FE analysis revealed that the stress state of the concrete cross‐section transitioned from uniform compression to coexisting compressive and tensile zones with increasing e 0 /h , accompanied by an increase in peak stress. Meanwhile, the stress distribution of the light steel skeleton shifted from uniform to a gradient form, with the peak stress in the high‐stress zone approaching 3.1 × 10 2 MPa. The proposed FE model provides a theoretical foundation for future in‐depth investigations into the key factors influencing the axial and eccentric compressive behavior of this type of composite column along its strong axis.