Parametric Study on the Effect of Axial Force on the Seismic Performance of the Bar Damper

Abstract

A bar damper (BD) is an energy-absorbing device that, despite its simplicity, exhibits excellent energy absorption capacity. The parametric studies in this research focused on the effect of axial force on the cyclic behavior of these dampers. Initially, to verify the results of the numerical model, three experimental BD samples with different heights were utilized. After calculating the buckling load of BD, the effect of 2% and 4% of this load on its cyclic behavior was investigated. The effect of axial force and damper dimensions on its seismic parameters was assessed through nonlinear static analyses. These parameters included initial and effective stiffness, strength, energy dissipation, and equivalent damping ratio (EDR). Additionally, based on the curve fitting method for estimating the initial stiffness of the damper under axial force, an approximate equation was provided, which showed acceptable accuracy compared to the numerical results. The results indicated that the axial force led to a reduction in elastic stiffness, effective stiffness, and strength of the damper, especially at large deformations. The impact on energy dissipation was negligible, but it caused an increase in the EDR. The greatest impact of the axial force was observed on the strength, followed by its effect on the EDR.