Preliminary considerations on the selective weakening of RC columns through rocking systems

Most of the research on seismic retrofit approaches focuses on the development of innovative retrofit solutions with the aim to improve the seismic performance of existing buildings through either local or global strengthening. An effective alternative approach is controlling the seismic performance of existing buildings through the selective weakening of specific portions of the structure, particularly to reduce stiffness irregularities. The present research focuses on a possible weakening approach dealing with the transformation of the existing reinforced concrete (RC) columns of a given story, specifically at the ground level, into rocking columns. This solution will lead to a global behavior like the one of an isolated system. The advantages of such a solution are, among others: the reduction of the relative displacement demand at the stories above the rocking system (i.e., damage reduction at the upper stories), the reduction of damage in the RC columns through a confined rocking region, the lumping of the construction works at just one story, the possibility to couple the rocking columns with additional energy dissipation or recentering systems. The effectiveness of the proposed solution has been preliminarily evaluated through the application to a reference case study.