Étude du comportement des amortisseurs métalliques en U sous charges cycliques en vue de leur utilisation pour l’isolation sismique au Canada

Abstract

Seismic base isolation is recognised as an effective solution for improving the earthquakeresistant design of bridges. It reduces the seismic force demand while controlling seismic displacements. However, conventional bearing devices, such as reinforced natural rubber bearings (NRBs), have limitations including insufficient energy dissipation capacity, which precludes their use as isolation systems. This master thesis explores the development and optimisation of metallic U-shaped dampers (UD), designed to be combined with NRBs to improve their overall performance, as seismic isolators, and meet the requirements of the latest seismic standards. The study combines analytical, numerical and experimental approaches to quantify the key parameters of the hysteretic behaviour and fatigue resistance of UDs under different types of loading: monotonic, cyclic and fatigue. Two main geometries (UD1 and UD4) and three steel grades (260W, 350W and B400) were considered. The results show that geometry and load orientation have a strong influence on the mechanical response and durability of UDs. The more limited impact of steel grades mainly influences the maximum forces generated. Service fatigue tests also reveal a correlation between degradation of unloading stiffness and device failure. The analytical and numerical models validated in this thesis reliably predict the initial stiffness and yield strength of UDs. However, adjustments are required to capture the complex behaviour associated with out-of-plane deformations and torsional phenomena. Ultimately, recommendations are made for optimising UDs and exploring hybrid NRB-UD systems, thereby meeting the new requirements of seismic standards.

Date	28 Jan 2025
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Lotfi Guizani (Supervisor) & Najib Bouaanani (Co-supervisor)