Special T-shaped composite columns with concrete-filled square steel tubulars have good restraint on internal concrete, are convenient to process, have a high bearing capacity and good mechanical properties, and can increase the aesthetics of the building and the utilization rate of indoor space. Theoretical analysis, experimental study, and numerical simulation of the eccentric compression performance of the special-shaped column are carried out. Taking the specimen length, eccentric distance, and eccentric direction as test parameters, nine specimens with different slenderness ratios were designed to carry out eccentric compression tests. The eccentric compression performance was numerically simulated and analyzed by the general finite element software ABAQUS. The results show that the short column mainly suffers section strength failure, while the middle and long columns mainly suffer bending instability failure without torsional deformation. The degree of influence of the test parameters decreases in turn according to the eccentric distance, eccentric direction, and length of the specimen; there is no weld cracking phenomenon, and the square steel pipes can work together. The finite element calculation results are in good agreement with the experimental and theoretical values.

In order to expand the applications of cold-formed thin-walled steel structures, this study proposes a new type of composite wallboard composed of cold-formed thin-walled C-shaped steel and multi-layer concrete, in which C-shaped steel serves as the skeleton, foam concrete acts as the thermal insulation material, and fine aggregate concrete and cement mortar play the part of envelopes. The composite wallboard can be made in a factory assembly line, meeting the requirements of the building (civil and structural) industry. Two steel-frame composite wallboard shear walls were subjected to reciprocating loading, with the connection mode as the design parameter, to investigate the seismic performance of the structure. The failure mode, hysteresis curve, skeleton curve, strength degradation, stiffness degradation, ductility, and energy dissipation capacity of the specimens were analyzed. On this basis, the finite element (FE) model of the steel-frame composite wallboard was established, and the model’s accuracy was verified by comparing the bearing capacity and the skeleton curve. Results show that the structure shows shear failure characteristics, and the cement mortar layer and the fine aggregate concrete layer are separated from the C-shaped steel after being crushed. The infilled foam concrete is also crushed, and the welding seams between the extended C-shaped steel and steel frame of the WP-1 specimen are damaged. The hysteresis curves of the two specimens have a clear pinch, but the area enclosed by the hysteresis loop is large, and the energy dissipation capacity is also present. The yield load and ultimate load of the WP-2 specimen are higher than those of the WP-1 specimen, indicating that the higher the connection strength between the composite wallboard and the steel frame, the greater the ultimate carrying capacity of the specimen. The established FE model can accurately estimate the seismic performance of steel-frame composite wallboard shear walls.