The Seismic Retrofit by External Dissipative Systems: A Case Study

Abstract

External dissipative systems are seismic retrofit solutions for existing building frames that present some feasibility advantages with respect to more classic solutions involving dissipative devices installed within existing frames. This study analyses and compares the effectiveness of three alternative external retrofit configurations based on the use of fluid viscous dampers (FVDs) with reference to a case study involving the seismic upgrading of a typical school r.c. frame. In particular, the three considered systems are: a rocking base system consisting of a pinned-rocking braced frames equipped with fluid viscous dampers at their base, a fixed base system consisting of external fixed-base braced frames connected to the frame through dampers located at floor levels and a diagonal bracings system similar to the traditional arrangement, but installed adjacent to the frame. All the proposed retrofit solutions are analysed taking into account the non-linear behaviour of the r.c. frame building (designed with inadequate seismic detailing) and both the linear and non-linear behaviour of the FVDs. The obtained results show that all the systems are effective solutions, even if performances in terms of interstorey-drifts, absolute floor accelerations, forces and strokes of the dampers are different.

Building Back Better: The Case Study of the Fazzini College

“…The three configurations have mainly the same ability in reducing the IDR demands, even though the RB system is the only able to linearize the deformation profile (i.e., constant IDRs distribution). Such linearization, however, have a cost in terms of exchange actions between the building and the external bracing [20]. The FB system, instead, is the one able to provide the higher reduction of PFA, that are a response parameter particularly significant for nonstructural components, contents, and plants.…”