Device uncertainty propagation in low‐ductility RC frames retrofitted with BRBs for seismic risk mitigation

Abstract

Passive control systems, such as buckling‐restrained braces (BRBs), have emerged as efficient tools for seismic response control of new and existing structures by imparting strength and stiffness to buildings, while providing additional high and stable energy dissipation capacity. Systems equipped with BRBs have been widely investigated in literature; however, only a deterministic description of the BRBs’ properties is typically considered. These properties are provided by the manufacturer and are successively validated by qualification control tests according to code‐based tolerance limits. Therefore, the device properties introduced within the structure could differ from their nominal design estimates, potentially leading to an undesired seismic performance. This study proposes a probabilistic assessment framework to evaluate the influence of BRBs’ uncertainty on the seismic response of a retrofitted RC frame. For the case study, a benchmark three‐story RC moment‐resisting frame is considered where BRBs’ uncertainty is defined compatible to the standardized tolerance limits of devices’ quality control tests. This uncertainty is implemented through a two‐level factorial design strategy and Latin hypercube sampling technique. Cloud analysis and probabilistic seismic demand models are used to develop fragility functions for the bare and retrofitted frame for four damage states while also accounting for the uncertainty in the property of BRBs. Risk estimates are successively evaluated for three case study regions. The results show that, for the considered case study structure, these uncertainties could lead to an increase of fragility up to 21% and a variation in seismic risk estimates up to 56%.

Seismic Performance of Steel MRFS Retrofitted With Brbs: Influence of the Design Decisions for the Devices

“…Finally, the area and length of the BRBs is defined in accordance to the force and ductility requirements for the storey, while the area in the complementing elastic brace is defined in accordance with the stiffness requirements of the storey (i.e., with the elastic brace and BRB working in series). For a more in-depth discussion on the design method, the reader is referred to Freddi et al [26].…”

Effective placement of self‐centering damage‐free connections for seismic‐resilient steel moment resisting frames

“…Within this context, many recent research studies focused on the development of innovative seismic-resilient structures chasing the objectives of minimizing both seismic damage and repair time, hence allowing the definition of structures able to return to the undamaged, fully functional condition in a short time 7,8 . For this purposes, innovative technologies based on supplemental damping devices [9][10][11][12] and base isolation systems 13,14 have been widely investigated in the last few decades, and the application of some of these technologies is nowadays mature and becoming popular in many earthquake-prone regions. Among others, for steel moment resisting frames (MRFs), one viable solution is represented by the use of damage-free joints based on friction devices (FDs).…”

A fragility-oriented approach for seismic retrofit design

“…Kaplan et al, 2011;Miano et al, 2017) or bracing (e.g. Badoux and Jirsa, 1990;Freddi et al, 2013Freddi et al, , 2021Gutie´rrez-Urzu´a et al, 2021) to existing buildings notably improves stiffness and lateral strength. In contrast, base isolation is applied to reduce seismic demand by decoupling the horizontal motion of a structure and that of the ground (e.g.…”