Seismic Retrofit of Pilotis Buildings by Novel Aluminium Buckling-Restrained Braces (Al-BRBs). Application to a Modernist Architecture Building in Lisbon

Abstract

ABSTRACT The worldwide dissemination of the pilotis multi-storey RC buildings, generally attributed to the architect Le Corbusier, was contemporary with a structural engineering line of thought that advocated a soft first storey as a means of filtering down the seismic inertia forces in the upper storeys. These two architectural and structural international trends, combined with outdated detailing and low-code seismic design, greatly increase the risks of developing a soft storey sidesway mechanism at the first storey, as shown in past earthquake occurrences and other studies. The article explores the possibility of strengthening a representative 1955 pilotis building in Lisbon by the inclusion of novel aluminium buckling-restrained braces (Al-BRBs) at the first soft storey. This should reduce the extreme deformation concentration at that level without fully eliminating it, and thus take advantage of the additional damping provided by the stable hysteretic behaviour of the Al-BRBs. These Al-BRBs have some distinctive features that take advantage of the unique properties of the aluminium alloys, such as the formability (allowing for an extruded casing component) and the possibility of improving the low-cycle fatigue and deformation characteristics of the core component by means of thermal treatments.