Journal of Earthquake Engineering, 18:407–443, 2014 Copyright © A. S. Elnashai ISSN: 1363-2469 print / 1559-808X online DOI: 10.1080/13632469.2013.876946 The Effect of Stiffened Floor and Roof Diaphragms on the Experimental Seismic Response of a Full-Scale Unreinforced Stone Masonry Building ILARIA SENALDI 1 , GUIDO MAGENES 2 , ANDREA PENNA 2 , ALESSANDRO GALASCO 2 , and MARIA ROTA 3 1 Department of Civil Engineering and Architecture, University of Pavia, Pavia, Italy 2 Department of Civil Engineering and Architecture, University of Pavia and EUCENTRE, Pavia, Italy 3 European Centre for Training and Research in Earthquake Engineering (EUCENTRE), Pavia, Italy An extensive experimental program was carried out at EUCENTRE, within a research project on the evaluation and reduction of the seismic vulnerability of stone masonry structures. The main part of the experimental program has been devoted to the shaking table tests on three full-scale, two-story, single-room prototype buildings made of undressed double-leaf stone masonry. The first building tested was representative of existing unreinforced stone masonry structures with flexible wooden diaphragms, without any specific anti-seismic design nor detailing. In the second and third build- ings, strengthening interventions were simulated on structures theoretically identical to the first one, improving wall-to-floor and wall-to-roof connections and increasing diaphragm stiffness. In particu- lar, in the third specimen, steel and r.c. ring beams were used to improve the diaphragm connection to the walls and collaborating r.c. slab and multi-layer plywood panels were used to stiffen floor and roof diaphragms, respectively. This article describes the strengthening interventions applied to the third building prototype and presents the experimental results obtained during the shaking table tests. The results obtained permitted the calibration of a macroelement model representative of the nonlinear behavior of the structure. Keywords Shaking Table Test; Stone Masonry; Full Scale; Strengthening Strategies; Diaphragm Stiffening 1. Introduction Unreinforced stone masonry is a common construction technique in existing buildings in several parts of Italy and in other countries worldwide. Among the different masonry typologies of existing masonry buildings in Italy, stone masonry is rather common in mountain and rural areas but also in old historical centers of urban areas. On the other hand, probably undressed stone masonry is, with the exception of adobe, the most vul- nerable masonry typology, as also recognized by several post-earthquake damage surveys (as discussed, for example, in Rota et al.[2011] or Carocci [2012], D’Ayala and Paganoni Received 18 August 2012; accepted 14 November 2013. This article is published under the JEE-Rose School Collaboration Agreement. Address correspondence to Andrea Penna, Department of Civil Engineering and Architecture, University of Pavia and EUCENTRE, Via Ferrata 3, 27100 Pavia, Italy. E-mail: andrea.penna@unipv.it Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/ueqe 407