Experimental and analytical investigation on the behavior of deformation-amplified torsional steel-tube dampers

A novel torsional steel tube damper with deformation amplification function (DATSTD) to address the issue that traditional metallic dampers cannot sufficiently dissipate energy under small deformation was proposed. The basic structure and working mechanism of the DATSTD were described. A theoretical restoring force model was derived, together with an amplification formula for the deformation and load-bearing capacity of the DATSTD. The seismic performance of the DATSTD with varying initial amplification angles was investigated by low-cycle cyclic loading test, and the energy dissipation and failure mechanism of the DATSTD were studied. A robust finite element model for the DATSTD was developed using the ABAQUS software, and the effect of the rotating plate length on the mechanical properties of the DATSTD was studied in detail. The test results show that the hysteresis curve of the damper is smooth and full, exhibits certain asymmetric features, and maintains a stable and efficient energy dissipation capacity. By reducing the initial amplification angle, the plastic deformation of the energy-dissipation steel tube progresses more extensively, the equivalent viscous damping coefficient rapidly increases to approximately 50 %, and the yield load, maximum load, and initial stiffness of the damper all increase significantly. While the asymmetry of the hysteretic curve is also slightly enhanced. The theoretical restoring force model and the finite element model could predict the performance of the DATSTD well. With reduction of the rotating plate length, the influence of the initial amplification angle change on the energy dissipation and load-bearing capacity of the damper would be increased. The maximum tensile-to-compressive load ratio of the damper would be increased and the asymmetry of the hysteretic curve becomes more pronounced as decreasing of the of the rotating plate length.