# Evaluation of Viscoelastic and Rotational Friction Dampers for Coupled Shear Wall System
## 1 Introduction
Full-scale experimental evaluations demonstrate that the viscoelastic coupling damper (VCD), as implemented in the prototype structure, effectively contributed to both viscous damping and shear stiffness within the coupled wall system. However, further advancements in viscoelastic damper design are necessary to enhance flexibility and optimize performance. A newly developed VCD system has been introduced to enhance the dynamic performance of high-rise buildings under wind and seismic loads. This system consists of viscoelastic material layers bonded between steel plates, with alternating steel layers extending to opposite sides and securely anchored to the structural walls, thereby optimizing energy dissipation and structural stability. VE dampers offer distinct advantages over metallic yield dampers and buckling-based energy dissipation systems due to their stable hysteretic behavior, minimal residual deformation, and velocity-dependent energy dissipation. Unlike metallic yield dampers [7; 8], which rely on plastic deformation and may suffer from low-cycle fatigue, VE dampers dissipate energy through viscoelastic shear deformation, ensuring consistent performance over repeated cycles without permanent damage. Additionally, systems like energy-early-dissipated braces [9] depend on steel web buckling, which can lead to unpredictable post-buckling behavior and require complex detailing. In contrast, VE dampers provide predictable stiffness and damping across a wide frequency range, making them ideal for both seismic and wind-induced vibrations. Their self-centering capability (near-zero residual displacement) further reduces post-event repairs compared to metallic systems, which often retain plastic deformations. While metallic dampers excel in high-force applications, VE dampers are superior in scenarios requiring smooth, fatigue-resistant, and maintenance-free operation, particularly in buildings where serviceability and long-term reliability are critical. Friction dampers are among the most effective and widely utilized solutions for vibration control. These devices operate by dissipating vibration energy through frictional sliding between contact surfaces. In 1989, [PERSON] et al. introduced a classical friction-based energy dissipation mechanism known as the slotted bolted connection to improve the seismic response of ordinary brace frame and braced moment resistance frame [10]. Friction-based energy dissipation systems have been implemented in various structural components to mitigate seismic-induced plastic damage and enhance earthquake resilience. Their widespread adoption is attributed to their high energy dissipation efficiency, ease of maintenance, and rapid post-earthquake repairability. Applications include damage-free beam-column connections [11; 12; 13; 14; 15], rocking timber walls with slip-friction connectors [16], and steel column bases incorporating friction devices [17; 18]. More recently, in 2022, [PERSON] et al. [19] proposed a ductile bracing system incorporating a rotational friction damper joint, characterized by an eccentric placement relative to the bay diagonal. A ductility-based design methodology was developed for structures utilizing this system, and a three-dimensional structural model was designed and analyzed through various analytical approaches. The findings demonstrated that the proposed damper-brace system and associated design methodology are effective for practical implementation. Additionally, [PERSON] et al. [20] modified the rotational friction damper for bracing applications by introducing a square-shaped configuration, designed specifically for installation within square spans. The results indicated a significant reduction in lateral displacements and base shear in multi-story buildings equipped with this modified energy dissipation device, highlighting its efficiency in dissipating seismic energy. The ultimate goal of this research is to develop a hybrid damper that combines a VE damper and a RF damper.