Cycle behavior of U-shaped damper with a multi-phased yield mechanism

The advantage of using yielding dampers with a multi-phase yielding mechanism (MPYM) is that the dampers yield gradually, preventing the dampers from suddenly losing stiffness and strength. The study investigated the numerical and analytical behavior of U-shaped dampers (UD) with an MPYM. Initially, the numerical model was calibrated using experimental and analytical data. Then, extensive parametric analyses were conducted to investigate UD with an MPYM. The model's variables encompassed the dimensions of the UD and their number in the model. The effects of these variables on elastic and effective stiffness, energy dissipation, maximum strength, and equivalent viscous damping ratio (EVDR) were then calculated. Analytical equations were proposed to estimate the force-displacement diagrams of the models. In addition, approximate equations were presented to predict the effective stiffness, ultimate strength, and energy dissipation of the damper, making calculations simpler. The UD was yielded in order from the highest elastic stiffness to the lowest in the model. Increasing the ratio of elastic stiffness, yield strength, and the number of dampers in the model increased energy dissipation and EVDR. Comparing the MPYM damper with traditional dampers reveals that the models do not exhibit a significant decrease in strength and stiffness after the initial yield.