SEISMIC RETROFIT FOR RC BUILDINGS USING ELASTO-PLASTIC AND VISCOUS DAMPERS IMPLEMENTED WITH ELASTIC STEEL FRAMES

Learning from the past severe earthquakes, many reinforced concrete buildings were damaged because of insufficient lateral force resistance, stiffness, ductility, or energy dissipation capacity. Seismic design specifications in many countries are being updated in order to ensure safety from future earthquakes. Recent severe earthquakes around the world have proven that retrofitting of these buildings is an urgent matter. Seismic retrofit of a reinforced concrete building using dampers is proven to increase the energy dissipation capacity and seismic performance for the building. The available damper design approaches are required to iterate in order to calculate the required stiffness and equivalent damping ratio, which may lead to a complicated design. This study proposes a seismic retrofit design method using elasto-plastic or viscous dampers implementing with an elastic steel frame without iteration. The steel frame not only applies an interface between the dampers to the RC frame but also prevents damage concentration from limiting stories and secures the self-centering function. The proposed retrofitting method is based on the equivalent linearization approach, which efficiently distributes the dampers along with the building height in order to reduce the maximum story drift ratio of the buildings. The equations to evaluate the required dampers stiffness for elasto-plastic damper and the required damping coefficient for viscous dampers are introduced. A four-story reinforced concrete school building is used as a benchmark model, and nonlinear response history analysis is performed to verify the proposed retrofit method. The results suggest that the proposed retrofit method is considered to be effective in the example building. The maximum story drift ratio of retrofitted reinforced concrete building using both elasto-plastic and viscous dampers is reduced significantly when compared to the bare reinforced concrete building without retrofit, and the maximum story drift ratio is close to the design target story drift ratio.