Simplified indexes for the seismic assessment of masonry buildings: International database and validation P.B. Lourenço 1,* , D.V. Oliveira 2 , J.C. Leite 3 , J.M Ingham 4 , C. Modena 5 , F. da Porto 6 1, * Corresponding author. Professor, ISISE, Department of Civil Engineering, University of Minho, Azurém, P 4800-058 Guimarães, Portugal. Phone: +351 253 510 209, fax: +351 253 510 217, email: pbl@civil.uminho.pt 2 Associate Professor, ISISE, Department of Civil Engineering, University of Minho, Azurém, P 4800-058 Guimarães, Portugal. Email: danvco@civil.uminho.pt 3 PhD Student, ISISE, Department of Civil Engineering, University of Minho, Azurém, P 4800-058 Guimarães, Portugal. Email: joaoleite@civil.uminho.pt. 4 Professor, Department of Civil and Environmental Engineering, University of Auckland, Auckland, New Zealand. E-mail: j.ingham@auckland.ac.nz 5 Professor, Department of Structural and Transportation Engineering, University of Padova, via Marzolo 9, 35131 Padua, Italy. E- mail: modena@unipd.it 6 Assistant Professor, Department of Structural and Transportation Engineering, University of Padova, via Marzolo 9, 35131 Padua, Italy. E-mail: francesca.daporto@unipd.it Abstract Heritage masonry buildings are particularly vulnerable to earthquakes because they are deteriorated and damaged, they were built with materials with low resistance, they are heavy and the connections between the various structural components are often insufficient. The present work details a simplified method of seismic assessment of large span masonry structures that was applied to a database of forty-four monuments in Italy, Portugal and Spain, providing lower bound formulas for different simplified geometrical indexes. Subsequently, the proposed thresholds are validated with data from the 2010-2011 Canterbury earthquakes, which includes forty-eight stone and clay brick masonry churches. Finally, fragility curves that can be used to estimate the damage as a function of the peak ground acceleration (PGA) are also provided.