# Evaluation of Viscoelastic and Rotational Friction Dampers for Coupled Shear Wall System
## 1 Introduction  
The coupled shear wall system has been introduced due to its superior lateral stiffness compared to other lateral force-resisting systems [1]. The incorporation of high-stiffness structural members enhances the control of lateral forces acting on buildings, effectively minimizing lateral deformations. This characteristic is particularly crucial for high-rise buildings, where structural design is predominantly influenced by dynamic lateral loads. Coupling beams facilitate shear force transfer between shear walls, thereby enhancing energy dissipation. Consequently, coupled shear walls are regarded as an optimal solution for achieving the desired strength, stiffness, and ductility in structures [2]. However, inadequate design capacity or excessive lateral loading may lead to structural deterioration, including flexural failure at coupling beam joints and the base of structural walls. The degradation of lateral stiffness due to excessive damage further complicates the control of structural vibrations, posing significant challenges in maintaining the building's overall stability. The VE damper represents a highly effective alternative for energy dissipation systems and has been widely utilized for wind and seismic protection of buildings for nearly five decades [3; 4; 5]. The implementation of VE dampers in coupled shear wall structures is particularly advantageous due to their dual function of enhancing stiffness and dissipating energy, thereby effectively mitigating drift and structural forces. In VE dampers, shear deformation is the primary mechanism for energy dissipation. When subjected to lateral forces, the viscoelastic material (typically a polymer) undergoes cyclic shear straining, causing internal friction and heat generation. The displacement-dependent force arises from the elastic component of the material, which stores energy as it deforms, while the velocity-dependent force comes from the viscous component, which resists rapid motion, converting kinetic energy into heat. Together, these forces create a hysteresis loop in the stress-strain curve, where the area enclosed represents energy dissipated per cycle. In practical terms, as the damper experiences seismic or wind-induced vibrations, the combined effect of elastic stiffness (resisting displacement) and viscous damping (resisting velocity) effectively absorbs and dissipates energy, reducing structural vibrations. Efficiency depends on the material properties, frequency of loading, and temperature, making VE dampers highly effective for mitigating dynamic responses in buildings and bridges. The implementation of dampers as substitutes for structural elements, such as coupling beams or outriggers, ensures that no usable architectural space is compromised. One effective approach involves embedding dampers within the coupling beams linking adjacent shear walls, utilizing the structural depth already allocated for beam reinforcement. For instance, compact viscous or viscoelastic dampers can be installed in staggered or diagonal arrangements within the beam midspan, where shear demands are highest, without encroaching on functional floor space. Under lateral or in-plane torsional deformation of the building, the relative displacement between walls induces differential vertical movement within the coupling elements, subjecting the VE material layers to shear deformation. This mechanism generates a force that is both displacement and velocity-dependent, thereby enhancing wall coupling and providing supplemental viscous damping to the overall structural system. Proper distribution of dampers along the building's height enhances supplemental viscous damping across all lateral and torsional vibration modes, effectively mitigating dynamic responses to wind and seismic excitations. [PERSON]'s research [6] confirms the efficacy of viscoelastic coupling dampers in improving the dynamic performance of high-rise buildings.