Stability and seismic analyses of leaning towers: the case of the minaret in Jam Paolo Clemente 1 * , Fernando Saitta 1 , Giacomo Buffarini 1 and Laura Platania 2 1 ENEA, Casaccia Research Center, Rome, Italy 2 Visiting architect, ENEA, Rome, Italy SUMMARY The leaning Minaret of Jam, one of the tallest in the world, was declared as the Afghanistan’s first World Heritage Site by UNESCO in 2002. The global stability analysis of the tower against soil collapse is first evaluated in the present configuration, in the hypothesis of increasing bending moment at the base section, assuming elastic-perfect plastic behavior for the soil. Then, a finite element model is set up, which is used for the modal analysis and then for the seismic push-over analysis, based on both single and multi-modal approaches. Copyright © 2014 John Wiley & Sons, Ltd. Received 7 June 2013; Revised 27 November 2013; Accepted 14 January 2014 KEY WORDS: stability; minaret; leaning tower; masonry tower; seismic analysis 1. INTRODUCTION Monuments and historical buildings, with their cultural, historical and artistic value, need a particular seismic protection. High rise structures, such as masonry towers, have a particular vulnerability, higher than other structural types. As a matter of fact, even a low intensity earthquake could cause the partial or total collapse. Besides, quite often, masonry towers are leaning, although this is not always very apparent (Heyman, 1992; Macchi, 1998). So is the Minaret of Jam, object of this paper, which in its current configuration presents a significant tilt angle with respect to the vertical. In these cases, detailed studies are needed, which include the historical analysis, the knowledge of the present configuration and the analysis of the all possible collapse mechanisms. Besides, a complete safety analysis cannot leave aside neither the geotechnical aspects nor the structural ones. There are several examples of investigators in the literature, which focused their attention to leaning towers. A well-known example is the Pisa tower (Cheney et al., 1991; Burland et al., 2003). Also, several studies on structural behavior of minarets have been conducted. Among the most recent works, it is worth mentioning the linear dynamic analyses of three minarets different in height, modeled by means of solid finite elements (FEs) (Dogangun et al., 2008) and those of several minarets in Istanbul, also supported by experimental measurements (Oliveira et al., 2012). The former, as a result from computa- tional models, indicates that the largest flexural and axial stresses are at the top of the transition segment, associated to a reduction in cross-section. Large shear forces are near the bottom of the minaret. Also, the latter paper evidences as higher tensile stresses occur at transition zones and at balconies levels, where mass increases. A proposal for the seismic isolation of Mamluk-style minarets, combined with vertical anchor bars, is in the paper of El-Attar et al. (2005). A stochastic analysis of the Ulu Mosque minaret under seismic and blast loads was performed by Haciefendioğlu and Birinci (2011). Nonlinear analyses, involving models for materials and damage, have been carried out by different authors (Mortezaei et al., 2012; Peña et al., 2010). A biaxial orthotropic hypo-elastic concrete model *Correspondence to: Paolo Clemente, ENEA, Centro Ricerche di Casaccia, Via Anguillarese 301, Rome 00123, Italy. E-mail: paolo.clemente@enea.it THE STRUCTURAL DESIGN OF TALL AND SPECIAL BUILDINGS Struct. Design Tall Spec. Build. (2014) Published online in Wiley Online Library (wileyonlinelibrary.com/journal/tal). DOI: 10.1002/tal.1153 Copyright © 2014 John Wiley & Sons, Ltd.