PSI - Issue 44

Ciro Del Vecchio et al. / Procedia Structural Integrity 44 (2023) 1411–1418 Ciro Del Vecchio et al. / Structural Integrity Procedia 00 (2022) 000 – 000

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1. Introduction Recent seismic events demonstrated that existing unreinforced masonry (URM) buildings in the Mediterranean are vulnerable to seismic actions(Sorrentino et al. 2019). This is because of poor quality of the masonry and lack of proper seismic details (e.g. appropriate floor-to-wall connection, weak connection between orthogonal walls). These weaknesses may significantly compromise the building response under lateral loads often resulting in marked diagonal cracking (see Fig. 1a on the left) or the initiation of first mode mechanisms with the out-of-plane overturning of the masonry panels (see Fig. 1a on the right). These are some of the typical damage observed in the post-earthquake inspections in the aftermath of recent earthquake events in Italy leading to number of fatalities and massive economic losses(Dolce and Manfredi 2015; Di Ludovico et al. 2017).

Nomenclature l e

embedded length of the anchor width of the mortar sample heigh of the mortar sample

w

h

l

distance between supports in three-point bending test

F

maximum recorded force

R c R f

compressive strength of the mortar flexural strength of the mortar

(a) (b) Fig. 1. (a) In-plane and out-of-plane damage of perimetral wall due to the 2016 Central Italy earthquake; (b) performance of a URM building with injected anchors. On the other side, the recent Central Italy earthquake showed the effectiveness of retrofit interventions increasing the seismic performance of URM buildings (see Fig 1b). Indeed, buildings that were retrofitted during the reconstruction process followed to the Umbria-Marche earthquake (1997) showed lower damage than unstrengthened ones (Sisti et al. 2022). This remarked the importance of the retrofitting as seismic prevention strategy to contain earthquake damage, fatalities and economic losses. Many retrofit strategies can be used to increase the seismic capacity of URM (Elgawady et al. 2004). For instance, the in-plane capacity of walls can be improved by classic or innovative FRCM jacketing (Garofano et al. 2016). However, as also suggested by the Italian guidelines for seismic risk assessment (Cosenza et al. 2018), to effectively improve the seismic performance of existing URM building a good connection between all the walls should be guaranteed.