Seismic Response of a Historical Masonry Minaret using a Finite Element Model Updated with Operational Modal Testing Alemdar Bayraktar, Ahmet Can Altunis ¸ik, Baris ¸ Sevim and Temel Tu ¨ rker Abstract This paper presents the earthquake response of a historical masonry minaret after a finite element model updating was undertaken using the information from full scale ambient vibration testing. The _ Iskenderpas ¸a historical masonry minaret dating back to the 16th century with a height of 21m located in the city center of Trabzon, Turkey is selected as an application. Analytical modal analysis is performed on the 3D finite element model of the minaret considering field survey and engineering judgments to obtain the analytical frequencies and mode shapes. The field ambient vibration tests on the minaret under natural excitations such as wind loading and human movement are conducted. The Peak Picking and the Stochastic Subspace Identification techniques are used to extract the modal parameters from the ambient vibration test. A good correlation was found among the modal parameters identified from the two techniques. The finite element model of the minaret is updated to minimize the differences between analytically and experimentally estimated modal properties by changing some uncertain modeling parameters such as material properties and boundary conditions. The analytical model of the minaret after finite element model updating is analyzed using the 1992 Erzincan earthquake record, which occurred near the area, to determine the earthquake behavior of the minaret. At the end of the study, maximum differences in the natural frequencies are reduced on average from 27% to 5% and a good agreement is found between analytical and experimental natural frequencies and mode shapes by model updating. Also, it is seen from the earthquake analysis that the displacements increase along the height of the minaret and the maximum and minimum principal stresses occur at the region of the transition segment and the cylindrical body. Keywords Ambient vibration testing, earthquake behavior, finite element model updating, _ Iskenderpas ¸a historical masonry minaret, modal testing, peak picking, stochastic subspace identification Received: 21 July 2008; accepted 5 October 2009 1. Introduction In the last decade, the conservation and the structural safety assessment of ancient masonry structures such as minarets and towers have become of increasing concern, probably as a consequence of some dramatic events registered in Europe, like the sudden collapse of the Civic Tower in Pavia, Italy (Binda et al., 1992, 1995), the bell-tower of St Magdalena in Goch, Germany and the Cathedral of Noto in Italy (Binda et al., 2003) (Figure 1), the collapses of the C ¸ ınarlı minaret in Balıkesir [URL-1], the Merkez minaret in Ankara [URL-2], the Yu ¨reg ˘il minaret in Afyonkarahisar [URL-3], and the C ¸ avdır minaret in Antalya [URL-4], 1 Turkey (Figure 2). The restoration of the Yenicuma and _ Iskenderpas ¸a minarets in Trabzon (Zorlu and Ataman, 2007) (Figure 3), the Torrazzo tower in Cremona (Binda et al, 2000), the Civic Tower in Vicenza (Valluzzi et al., 2003), and the St Stefano bell-tower in Venice (Balduzzi et al., Department of Civil Engineering, Karadeniz Technical University, 61080, Trabzon, Turkey Corresponding Author: Alemdar Bayraktar, Department of Civil Engineering, Karadeniz Technical University, 61080, Trabzon, Turkey Email: alemdar@ktu.edu.tr Journal of Vibration and Control Reprints and permission: sagepub.co.uk/journalsPermissions.nav jvc.sagepub.com 17(1) 129–149 DOI: 10.1177/1077546309353288 ª The Author(s) 2011