Experimental study and numerical simulation on seismic performance of a self-centering deformation-amplified torsional steel tube damper

To address the limitations of conventional metallic dampers, which exhibit difficulty in yielding under small deformations and significant residual deformation under large deformations, this paper proposes a novel self-centering deformation-amplified torsional steel tube damper (SC-DATSTD). The structural configuration, working mechanism, and assembly process of the proposed damper are described in detail. Quasi-static cyclic loading tests were conducted to investigate its hysteretic behavior, with a focus on key performance indicators, including failure mode, load-bearing characteristics, energy dissipation efficiency, and self-centering capability. Furthermore, a refined finite element model was developed. Experimental results indicate that the hysteresis curves exhibit a distinct asymmetric flag-shaped pattern. Reducing the initial amplification angle effectively enhances both the deformation and load-bearing amplification factors of the energy-dissipation system, significantly improves its energy-dissipation performance under low displacement levels, and increases the equivalent damping ratio by up to 43.3%, while maintaining stable self-centering capacity. Numerical simulation results show good agreement with experimental data, with maximum load errors across all loading stages remaining within 10% and nearly identical tension-compression load ratios. The reduction in the initial amplification angle leads to markedly increased plastic deformation in the energy-dissipation steel tubes, consistent with experimentally observed energy dissipation trends, thereby confirming that the finite element model accurately captures the working mechanism and hysteretic behavior of the damper.