Influence of Friction and Fluid Viscous Dampers on the Seismic Response of a Typical RC School Building with Different Concrete Strengths

Passive energy dissipation systems are among the effective retrofit strategies for improving the seismic performance of existing reinforced-concrete (RC) structures by limiting earthquake-induced demands and structural damage. This study aims to compare the seismic performance of friction dampers (FDs) and fluid viscous dampers (FVDs) in a typical RC school building with different concrete strengths. Accordingly, a total of six models, comprising unretrofitted (UR), FD-retrofitted, and FVD-retrofitted configurations for concrete compressive strengths of 14 MPa and 30 MPa, were developed and subjected to nonlinear time-history analyses using the Pazarcık and Elbistan ground-motion records from the 6 February 2023 Kahramanmaraş earthquakes. The FD and FVD systems were modeled using a common preliminary sizing approach, with the same damper arrangement and number of devices, based on a total nominal damper force corresponding to 30% of the elastic story shear force at each story. Structural response was evaluated in terms of natural period, displacement, interstory drift, story acceleration, shear forces, energy dissipation, structural member performance levels, and effective equivalent viscous damping. The results showed that both damper systems substantially reduced deformation demands and structural damage; however, their relative effectiveness varied depending on the concrete strength, ground-motion record, and response parameter considered. Under the conditions considered in this study, FDs provided greater reductions in some response parameters, whereas FVDs exhibited more balanced response control, higher energy dissipation ratios, and greater contributions to effective equivalent viscous damping, particularly under higher seismic demand. The findings highlight the importance of jointly considering concrete strength, seismic demand, and damper mechanism in the seismic retrofitting of existing RC structures.