Buildings with Friction-based Energy Dissipation Devices

Abstract

Recently introduced approaches based on the use of energy dissipation devices (EDDs) constitute an attractive strategy alternative to conventional approaches in seismic design wherein input energy is dissipated through plastic deformations in several regions of the structure, hence inducing significant damage throughout the structure. The EDDs release the main structure from dissipating energy and limit their role to only (or primarily) sustaining the gravity loads. The seismic resistance of the structure is provided entirely (or primarily) by the EDDs. Despite their major advantages, the use of EDDs is still very limited. However, as the concept of damage limitation gains increasing popularity (as a viable alternative to ‘classical’ ductility-based design) the use of EDDs is expected to increase, also (and perhaps to a larger extent) in retrofitting of existing structures.
The forthcoming ‘second generation’ Eurocode 8 includes for the first time, detailed provisions for the design of buildings with energy dissipation devices mainly in clause 9 of its Parts 1-2 which addresses the seismic design of new buildings. Part 3, dealing with retrofitting of existing structures, refers to the option of providing ‘passive protection devices through dissipative bracing or other dissipative devices’, but contains no specific provisions for them, simply referring to Part 1-2 (and to Part 1-1 for the general principles).
This study explores the feasibility of upgrading existing buildings with substandard seismic design using displacement-dependent dampers, which are an attractive option from a cost-benefit point of view. Following a critical discussion of the concepts involved, the new Eurocode 8 procedures are applied (for the first time, to the best of the author’s knowledge) to the retrofitting of a typical existing reinforced concrete frame structure designed to the 1960s codes. Friction dampers are introduced in selected locations of the building and are verified according to the ‘energy balance’ method of Parts 1-2, also accounting for the provisions of Parts 1-1 and 3.
As a result of retrofitting the building using EDDs based on Eurocode’s approach, the structure showed a visible enhancement in base shear (+72.7%), ductility (+26.6%), and drifts. The Eurocode’s design procedure is made for new structures, whereas applying it to existing structures requires a number of adjustments.

Date of Award	Aug 2023
Original language	American English
Supervisor	Andreas Kappos (Supervisor)