Numerical and analytical investigation of U-shape dampers and its effect on steel frames

Yielding dampers are one of the structural systems which dissipate a portion of the seismic force via premature yielding. The numerical and analytical methods were used in this study to investigate the behavior of the U-Shape Damper (USD) and its effect on steel frames. For this purpose at first, extensive parametric studies were performed using calibrated USD model. The parametric studies involved investigating the effect of USD di-mensions on its elastic stiffness, strength, effective stiffness, and equivalent viscous damping ratio. Finite element models were analyzed under cyclic loading using nonlinear static analysis. An analytical equation was then presented to estimate seismic parameters of the USD. In the second part, the effect of this damper on the steel frame was investigated using push over analysis. The seismic parameters of the frame, including elastic stiffness, strength, ductility, and energy dissipation, were investigated through 56 numerical models to determine the effects of the number of USDs and the axial force of the column. The results indicated that reducing the radius and increasing the thickness of the damper led to an increase in effective stiffness, energy dissipation, and strength, while reducing the equivalent viscous damping ratio. Furthermore, the results obtained from the steel frame equipped with a USDs revealed that the addition of the damper mitigates the adverse effects of axial force on the frame.