Experimental and Numerical Study of the Seismic Behavior of Single-Plane Trussed CFSST Composite Column Frames

A trussed concrete-filled square steel tubular (CFSST) composite column frame is proposed for multi-story residential buildings. The frame provides high lateral resistance and can be integrated within wall systems. To evaluate its seismic performance, three full-scale specimens were subjected to quasi-static cyclic loading. The failure modes, load-carrying capacity, stiffness degradation, and energy dissipation characteristics were examined and compared. The results show that, compared to the H-shaped steel column frame (HK) with equivalent steel consumption, the trussed CFSST composite column frame exhibits an 88.3% increase in yield load and an 87.1% increase in peak load, together with significant improvements in stiffness and energy dissipation. Compared with an ordinary CFSST column frame (FK), the proposed system required 41% more steel but attained a 56% increase in load-carrying capacity, along with corresponding enhancements in stiffness and energy dissipation. Finite element (FE) models were developed based on the experimental results, and parametric analyses were performed to investigate the effects of corner-end column spacing, number of truss diagonal bars, truss joint type, axial compression ratio, and steel strength. Design recommendations are provided accordingly.