# Evaluation of Structural Behavior of Hysteretic Steel Dampers under Cyclic Loading
## 1 Introduction  
One of most important purposes of building structures is to protect humans from nature, and design methods that reduce structural damage caused by external loads are constantly being developed. There are even methods being developed to mitigate damage caused by natural phenomena that are difficult to predict, such as earthquakes.  
Seismic design includes seismic resistance, seismic isolation, and seismic damping to design structures that are safe from earthquakes. Seismic resistance allows a structure to directly absorb seismic energy, and it can protect human life during a strong earthquake, but severe residual deformation due to the inelastic behavior of the structure results in enormous social costs and environmental pollution due to demolition. Seismic isolation is the best way to avoid earthquake damage by separating a structure from the ground, thereby rendering it unaffected by earthquakes. However, seismic isolation is difficult to apply to many buildings because the cost of the seismic isolator can be prohibitive. Finally, seismic damping allows the damping device, instead of the structure, to absorb the seismic energy. Damping devices can be divided into active and passive control systems. The active control system is relatively expensive and complex because it requires several mechanical devices. On the other hand, the passive control system is relatively simple and economical, and it can easily be replaced when retrofitting structures after an earthquake. For these reasons, passive control systems are widely used in building structures.  
Recently, many studies [1; 2; 3; 4; 5; 6; 7] have been conducted to induce dissipation of seismic energy by using the hysteretic characteristics of ductile steel. Applying metallic yielding dampers for the seismic retrofit to existing structures is becoming more common due to the convenience of manufacturing and installing them, along with their economic efficiency. The passive yielding damper system is generally composed of two types of components. One component is a rigid body that transmits energy induced by seismic load, and the other component dissipates the transmitted external energy. Since the performance of the damping system depends on the characteristics of the energy dissipation component, most research has been focused on how to develop this damper component.  
A study to dissipate earthquake-induced energy using the yielding of steel was first initiated by [PERSON] et al. [8] and [PERSON] et al. [9] in New Zealand. The steel dampers were developed in the form of ADAS (added damping and stiffness) dampers [10; 11], TADAS (triangular added damping and stiffness) dampers [12], buckling restrained braces [13], honeycomb [14], shear panels [15; 16; 17], slit [18; 19; 20; 21], and U-shaped dampers [22; 23]. These dampers can be applied to various structural members, such as walls, columns, beams, and braces of buildings, to absorb seismic energy. Although there have been many studies so far, efforts to develop better dampers that combine a simple form with excellent performance are still ongoing. In this study, a steel damper with a relatively simple shape and excellent energy dissipation and damping capacity was developed, and its structural performance was experimentally and analytically evaluated.