Investigation of using fluid viscous damper in RC buildings for prevention of soft story irregularity

In the study, the applicability of strengthening with Fluid Viscous Dampers (FVDs) was investigated for two RC buildings, one with four stories and the other with seven stories, in which soft-story irregularities were introduced by increasing the ground floor height and reducing the amount of infill walls. To eliminate the soft-story effect, FVD reinforcements were applied at selected spans only at the ground floor and building performances were assesed by nonlineer dynamic analysis. Two sets of earthquake records including far-fault and near-fault ground motion characteristics were selected. These records were scaled for both Design Basis Earthquake Level (DD-2) and Maximum Considered Earthquake Level (DD-1), and applied to the models. Three different FVD configurations targeting distinct performance objectives were investigated for each building. The first objective was to achieve Controlled Damage under the DD-2 earthquake level, which is the minimum (standard) performance objective defined in the 2018 Building Code of Turkey (BECT 2018). The other two advanced performance objectives aimed to achieve Limited Damage under DD-2 and Collapse Prevention under DD-1. The most appropriate FVD device characteristics in terms of force and displacement capasities were explored for these objective. Performance evaluations were primarily based on BECT 2018, with additional checks carried out according to ASCE 41-23 criteria. In addition to performance evaluation, the effects of FVD implementation on maximum and residual interstory drift ratios, base shear forces, and column axial forces were examined. For the four story building, all performance objectives except for Collapse Prevention under the DD-1 near-fault earthquake set were achieved. For the 7-story building, the minimum performance objective defined by BECT 2018 was met for both far-fault and near-fault records, but the other two objectives could not be achieved due to the upward shift of the soft-story irregularity to upper floors. Overall, the use of FVDs resulted in significant reductions in maximum and residual interstory drift ratios, while causing increases in base shear forces. The number of stories and the near-fault ground motion characteristics were significantly effective on the required capacities of the FVD devices.