Seismic Risks Mitigation of Façadism Constructions with Supplemental Energy Dissipation

Abstract

Urban renewal projects typically involve redevelopments of under-utilized old buildings and revitalizing precious land resources. Due to architectural and social-economic reasons, historical facades are sometimes retained, and new constructions are built behind them. This allows the historical facade, typically the street elevation, to remain while new real estate can be redeveloped. In the profession of architecture, this is called facadism. In many cases, these historical facades are constructed with unreinforced masonry (URM). When these facades are retained and the remaining of the building is demolished, they become free-standing walls. Temporary supports are required throughout construction works and the retained facades must be designed to prevent excessive movements, allowed for differential movements and to resist wind forces. These historical facades were made of brittle materials and were constructed many decades ago before modern design standards and materials are available. They possess very little ductility and become vulnerable when subjected to ground shaking. The present study suggests a structural system that attempts to mitigate seismic risk of facadism constructions effectively. The structural system divides the new construction, which can be a reinforced concrete structure or a steel frame structure, into two separate frames. A seismic gap is introduced between them and produces two systems of different vibrational characteristics. Supplemental energy dissipating devices such as viscous fluid or friction dampers are placed in-between adjacent floors. The proposed structural system utilizes the different vibrational responses of two frames to facilitate energy dissipation in dampers. In this article, governing equations are presented, followed by numerical simulations using historical earthquake acceleration histories. Results demonstrate that the suggested structural system is an effective methodology to suppress seismic responses of the facade and the new construction. It is concluded that damage on the retained facades can be prevented, and at the same time seismic responses to the newly constructed structure can be controlled.