## 1 Introduction  
During an earthquake, most structures have an inherent damping in them which results in some of the input seismic energy being dissipated, but a large amount of energy is absorbed by the structure, causing it to undergo several deformations and maybe even collapse. So, over the last year, there has been great interest in the creation of seismic energy dissipation devices that will absorb the majority of the seismic energy, but will not belong to the supporting structure of the construction (conventional braced frames). The main advantages of these are their easy replacement or repair. These devices belong to the passive energy dissipation systems, do not require external power to generate system control forces, and hence, are easy and cheap to implement in a structure [1, 2, 3]. Passive energy dissipation devices such as tuned mass dampers (TMD), viscous dampers (VD), and friction dampers (FD) have widely been used to reduce the dynamic response of civil engineering structures that are subjected to seismic loads. Their effectiveness for the seismic design of building structures is attributed to minimizing structural damages by absorbing the structural vibratory energy and by dissipating it through their inherent hysteresis behavior. The passive TMD is undoubtedly a simple, inexpensive, and somewhat reliable means to suppress the undesired vibrations. The TMD concept was first applied by [PERSON] in 1909 [4] to reduce the rolling motion of ships and ship hull vibrations. A theory for the TMD was presented later by [PERSON] and [PERSON] [5], followed by a detailed discussion of optimal tuning and damping parameters in [PERSON]'s book on mechanical vibrations [6]. A number of TMDs have been installed in tall buildings, bridges, and towers. The first structure in which a TMD was installed is the Centrepoint Tower in Sydney Australia, which was conceived in 1968 [7]. There are many buildings in the United States, like the Citicorp Center in New York City [8] and the John Hancock Tower in Boston [9]; in Japan, there is the Chiba Port Tower [10] and others [11]. A VD damper generally consists of a piston within a damper housing filled with a compound of silicone or a similar type of oil, with the piston containing a number of small orifices through which the fluid may pass from one side of the piston to the other [12]. Viscoelastic materials are very popular in engineering [13,14]. As the damper piston rod and piston head are stroked, fluid is forced to flow through orifices either around or through the piston head. The first applications of VD dampers to structures were for reducing acceleration levels, or increasing human comfort, due to wind. In 1969, VD dampers were installed in the twin towers of the World Trade Center in New York as an integral part of the structural system. In 1982, VD dampers were incorporated into the 76-story Columbia Sea First Building in Seattle, Washington, to protect against wind-induced vibrations [15]. Applying the well-developed fluid damping technology to civil structures was relatively straightforward; within a short time, the first research projects were completed on the application of fluid dampers to a steel framed building [12] and an isolated bridge structure [16]. In a typical FD, the generated frictional force helps to dissipate the external energy and stabilize the structure under the dynamic excitation scenarios. The FDs are also not prone to thermal effects, and possess a stable hysteretic behavior for a considerable number of cycles under such dynamic excitations [17]. Based primarily upon an analogy to the automotive brake, [PERSON] et al. [18] began the development of passive frictional dampers to improve the seismic response of structures. The objective is to slow the motion of buildings \"by braking rather than breaking\" [19]. After that, many researchers proposed friction dampers that focus on protection in the braced frames or in the joint connection [20, 21, 22, 23, 24, 25, 26, 27].