Real-Time Structural Monitoring of Bibi-Khanum in Samarkand (Uzbekistan) Combined with Subsequent Laser Scans

The Bibi-Khanum Mosque was originally built in 1399-1405 and was one of the largest and most magnificent mosques in the Islamic world during the 15th century. In recent years, the monument underwent several complex reconstructions. Among many other major restoration activities, the inner arch of the portal that collapsed in the 1897 earthquake was restored. The monument has been restored to be one of the best shapes in its history, thus it has become essential to conduct continuous structural health monitoring (SHM) of it to ensure its preservation for humanity. The SHM became the main objective of an ongoing extensive project, some results of which are presented herein. The structural health monitoring consisted of three major phases. The first phase includes a real-time monitoring of the monument by seismometers, which are permanently installed throughout the monument. They are used to monitor the effects of large and small earthquakes and ambient vibrations on the resonant frequencies of all major structures of the monument. By utilizing a system identification approach, the possibility of a structural anomaly development can be detected from the change in its resonance frequency. The second phase consists of subsequent laser scanning that is deployed to monitor anomalies of the monument’s geometry in 3D. The monument’s geometry is captured as a collection of points, which is called a “point cloud”. Laser scanning is planned to be conducted several times a year to capture global movements of the monument due to changes in the elevation of the underground water table in rainy and dry seasons. The third phase focuses on a development of a finite-element (FE) model based on the as-found geometry of the point clouds. It is calibrated based on the collected data to ensure acceptable correlations with the results of the measurements. The FE model is generated for use in future restoration efforts to evaluate the performance and efficiency (if any) of the proposed restoration measures. Based on the results of numerical simulations and structural health monitoring, preventive measures will be developed. In addition, recommendations for further preservation of the historic monument will be developed. This paper describes the preliminary results of the first phase and current results of the second phase of this multiphase project.

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