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

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 These two architectural and structural international trends, combined with outdated detailing and low-code seismic design, greatly increase the risks of developing a soft storey sidesway mechanism at the first storey, as shown in past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.

KEYWORDS:

• aluminium
• multi-storey buildings
• nonlinear static analysis
• nonlinear time-history analysis
• pilotis
• soft storey

Acknowledgments

The authors gratefully acknowledge the support provided by FCT-Fundação para a Ciência e Tecnologia (FCT), under of the InfraRisk Doctoral Program, through the PD/BD/135212/2017 PhD Grant to the second author. This work is part of the research activity carried out at Civil Engineering Research and Innovation for Sustainability (CERIS) and has been funded by FCT in the framework of project UIDB/04625/2020.

Some final words of acknowledgement go to Vasco Ribeiro for his crucial contribution to the development and analysis of the numerical model of the original building, performed as part of his MSc thesis in the IST-ULisboa (Ribeiro, 2021).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work was supported by the Fundação para a Ciência e a Tecnologia [PD/BD/135212/2017].