Numerical Modelling and Seismic Strengthening of a Stone Masonry 14th Century Tower: The Galata Tower, İstanbul

Abstract

The Galata Tower in Istanbul is a 14th-century stone masonry structure. After earthquakes, storms, and fire damage, the tower has been repaired several times. Between 1964 and 1967, the tower underwent significant repairs and reno-vations involving the addition of reinforced concrete. Most recently, the building was closed to visitors for renovation in 2024. This paper reports on the numerical analyses used to inform the retrofitting decisions taken for the final repair and the underlying data. The structural behaviour of the tower was difficult to understand due to uncertainties relating to the materials and past interventions. For this rea-son, numerical models were created using all available structural data to inform retrofitting decisions. The structure under investigation was modelled to approxi-mately represent its current state using finite element software, based on documents provided to the researchers and on-site examinations. A structural performance analysis was performed using the nonlinear pushover analysis method. A pushover analysis was conducted using OpenSees, a software package offering advanced nonlinear analysis capabilities. The ‘Damage TC3D’ plastic material model was used, considering masonry elements’ tensile and compressive strength limits and reductions. This material model is a more effective application of mixed implicit-explicit analyses. Displacement-based pushover analyses were performed, and the damage patterns and ultimate strength were obtained effectively. Finally, a retrofitting procedure aimed at improving the seismic capacity is proposed. The analyses conducted for the current status of the structure were repeated for the pro-posed retrofitting method. The results of both analyses are then compared to reveal the effects of the retrofitting proposals on the structure’s seismic performance.