Seismic performance of precast columns with cold-formed steel tenon and UHPC connections: Experimental and numerical investigation

To enhance both construction efficiency and seismic resilience of precast concrete systems, a novel column joint incorporating cold-formed steel (CFS) tenons and ultra-high-performance concrete (UHPC) is proposed. Low-cycle reversed loading tests were performed on three specimens with different axial compression ratios, and validated finite element (FE) models were used for parametric investigation. Failure characteristics, hysteretic behavior, strength, ductility, and the influence of key design parameters were systematically assessed. Results indicate that the overall failure remained flexure-dominated, while local concrete damage became more pronounced with increasing axial compression ratio; the specimens nevertheless exhibited stable hysteretic responses and good energy-dissipation capacity. The proposed composite joint effectively protects the core connection zone and promotes plastic hinge migration from the column base to the normal concrete (NC) segment. FE parametric analysis further shows that increasing the axial compression ratio from 0.2 to 0.8 enhances the peak load-carrying capacity, while the deformation capacity decreases markedly at axial compression ratios of 0.7 and 0.8. The seismic response is strongly governed by the spatial arrangement of the UHPC joint region. Among the investigated cases, placing the UHPC joint region at or close to the column base provides relatively favorable deformation performance, provided that its height is sufficient to cover the potential plastic hinge zone. Excessive UHPC height may induce stiffness discontinuity and deformation localization, while increasing keyway depth beyond basic anchorage requirements yields only marginal gains. These findings provide practical guidance for seismic design and optimization of high-performance precast column joints.