Evaluation of different types of advanced analysis for the study of the seismic behavior of masonry minarets

Numerical methods are considered effective tools for assessing the structural response of various types of buildings, including historic structures. As slender structures, minarets are vulnerable to loading and deformation, including seismic loads. This study aims to explore various numerical tools for evaluating the seismic response of a masonry minaret. Within this context, a structural assessment was conducted on a typical minaret that exhibits common characteristics of minarets. Pushover analysis with uniform and modal lateral load distribution patterns was carried out, accounting for physical and geometric nonlinearities, with results presented in terms of displacements and damage patterns. Subsequently, dynamic time history analysis was performed by applying the Bam earthquake records at the model's base. To further investigate the minaret's response to dynamic loads and to identify the failure mechanisms, the incremental non-linear dynamic analysis was carried out, scaling the Bam records to 0.5, 0.4, 0.3, 0.2, and 0.1.

The study's results demonstrated the effectiveness of finite element analysis in assessing the seismic behavior of minarets. Two failure mechanisms were revealed. The concentrations of tensile and shear stresses at the junction between the transition segment and the cylindrical body of the minaret were identified as the leading causes of the collapse. The results denote that the proposed scaling approach in non-linear dynamic analysis can precisely capture the damage propagation in the structure compared to the pushover analysis. In terms of maximum displacement, the nonlinear dynamic analysis produced more accurate results by incorporating all forces involved in the dynamic equilibrium and capturing the structure's full response to the ground motion's varying amplitude and frequency content compared to the pushover methods, which rely on static force distributions. Finally, the study concludes that the pushover analysis is conservative for slender masonry structures. It identifies damage-prone areas but misses dynamic effects and progressive damage. While useful for preliminary assessments, it is insufficient for safety evaluation. However, the nonlinear dynamic analysis provided a more detailed prediction of the damage pattern and illustrated damage progression in the minaret over subsequent stages.