Seismic Risks Mitigation of Façadism Constructions with Supplemental Energy Dissipation

Urban renewal projects involve redevelopments of under-utilised old buildings and revitalisation of precious land resources. Due to architectural and social-economic reasons, historical façades are sometimes retained, and new constructions are built behind them. This allows the historical façade, typically the street elevation, to remain while new real estate can be developed. In the profession of architecture, this is called façadism. In many cases, these historical façades are constructed with unreinforced masonry (URM). During demolition and construction, a temporary shoring retention frame is required prior to permanent connection to the new construction. These historical façades were made of brittle materials and were constructed many decades ago before modern design standards and materials were available. They possess little ductility and become vulnerable when subjected to ground shaking. Typically, the retained façades are treated as non-structural components and little attention is paid to their seismic performance. While most prior studies focus on strengthening of masonry or improving connection robustness between façades and the main structure, the present study attempts to take a different approach by limiting displacement demand on the façade. A new structural form is suggested which divides the new construction into two separate frames. A seismic gap is introduced between them and produces two structures of different vibrational characteristics. Supplemental energy dissipating devices such as viscous fluid or friction dampers are placed in-between adjacent floors. The façade is attached to a frame with smaller seismic mass and higher stiffness, while the second frame will undergo larger displacements in an event of ground shaking. In this manner, full advantage of supplementary energy dissipation is utilised, while protecting the façade from excessive displacements. In this article, governing equations are presented, followed by numerical simulations