Preliminary Numerical Analysis of the Seismic Response of Steel Frames With Masonry Infills Retrofitted by Buckling Restrained Braces

Abstract

Existing steel moment-resisting frames in several seismic regions worldwide are often characterised by high vulnerability to earthquakes due to insufficient local and/or global ductility. Nowadays, it is of paramount importance to assess their response under strong motions and provide cost-effective retrofitting strategies. Amongst others, the seismic behaviour of these frames is often strongly affected by the presence of masonry infills which, from one side, if adequately distributed, beneficially contribute to the seismic resistance of the structure providing stiffness and strength to the frame, from the other side often experience a brittle behaviour and are very vulnerable to seismic actions. To this end, the H2020-INFRAIA-SERA project HITFRAMES (i.e., HybrId Testing of an Existing Steel Frame with Infills under Multiple Earth-quakeS) experimentally evaluated a case study building representative of non-seismically designed European steel frames with masonry infills and investigated a possible retrofit strategy. This paper takes advantage of the experimental results of the HITFRAMES project to calibrate numerical models in OpenSees of a case study building which is analysed as bare, infilled and retrofitted frame with buckling-restrained braces (BRBs). The impact of masonry infills and BRB-retrofit is investigated by comparing the response of models with different configurations.

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.…”