Nonlinear analysis of historical Toptaş minaret and FRP strengthening for sequence earthquake events

Abstract

On February 6, 2023, a series of catastrophic earthquakes struck Turkey, causing extensive damage to historical structures, including the minaret of the Toptaş Mosque in Malatya. This minaret, comprising a stone base and masonry brick upper sections, suffered significant cracking, raising critical concerns regarding its structural stability and preservation. This study evaluates the seismic performance of the minaret under sequential two identical earthquake loading and investigates the efficacy of retrofitting using Fiber-Reinforced Polymer (FRP) as a strengthening solution. Nonlinear dynamic analyses (time history) were performed using the Applied Element Method (AEM) in ELS software to simulate the behavior of the minaret under seismic forces. Results indicated that, while the minaret could withstand a single earthquake, it experienced complete structural collapse under sequential events. To mitigate this vulnerability, FRP strips (100 mm × 2 mm) were applied to the interior surface of the minaret to enhance its structural resilience while preserving its historical appearance. Post-retrofitting analyses revealed significant improvements in the minaret’s seismic response. The lateral displacement at the top of the minaret decreased from 173.8 mm to 80.74 mm under a single earthquake. The maximum principal stress decreased to 5.4 MPa, within acceptable limits, demonstrating effective stress redistribution. Additionally, following two sequential identical earthquakes, the retrofitted minaret remained stable with a top displacement of 193.7 mm, highlighting its enhanced resistance to cumulative seismic forces. These findings underscore the effectiveness of FRP retrofitting in improving the seismic resilience of historical masonry structures. This study provides a scientifically robust framework for preserving architectural heritage by integrating advanced retrofitting techniques with structural analysis methodologies, ensuring the stability and longevity of heritage structures in seismically active regions.