Numerical study on the seismic response of a 1970s reinforced concrete building strengthened with concentric bracings

The paper presents the design of the seismic-retrofit of a reference existing reinforced concrete building (RC) designed for gravity loads only and built in Northern Italy in the 1970s. Concentric X-bracings made with steel plates are placed within the outer RC frame to enhance the lateral strength and stiffness of the building. The numerical results of non-linear push over and dynamic numerical analysis show the capacity of the proposed solution to meet the displacement demands of appropriately scaled natural accelerograms characteristic of a moderate seismic zone, with a lateral drift of less than 0.5% uniformly distributed over the building height.