Seismic fragility curves of a historical brick masonry minaret

Historical minarets are generally vulnerable to earthquakes because of their poor-quality materials and high slenderness. The objective of this work is to utilize the methodology employed for seismic fragility curves to analyze historical brick minarets, specifically focusing on a specific instance minaret. For this, the minaret of the Hocaalizade Mosque, built in Bursa during the Early Ottoman Period, was chosen. Using the software Abaqus v6.13, the minaret’s finite element model was constructed utilizing shell elements for the minaret and the walls of the mosque, and wire elements for the stair. The model was updated in accordance with the operational modal analysis (OMA) that was carried out in the field. Subsequently, IDA curves were generated for the minaret using Nonlinear Incremental Dynamic Analysis, utilizing 11 actual ground motion records with two horizontal components. A probabilistic approach was utilized in order to acquire the fragility curves for each performance level, which included limited damage, controlled damage, and collapse prevention. The outcomes of nonlinear time history analyze indicate that the minaret sustains damage mostly in two areas: between the transition and shaft, and/or between the balcony and the upper part. The analyses yielded fragility curves using two intensity measures as spectral acceleration and peak ground acceleration. The statistical assessment and regression analyses between each intensity measure and the probability of exceedance indicate that both intensity measures can be considered appropriate for the studied minaret. This minaret experiences the collapse prevention limit when the spectral acceleration (peak ground acceleration) exceed ∼0.27g (0.13g), respectively, with a ∼50% likelihood.