Seismic Assessment of the World’s Tallest Pure-Brick Tower Including Soil-Structure Interaction

One of the brilliant and exquisite structures in Iranian architecture is the Gonbad-e Qabus tower which was built on the Gorgan Plain in 1006 AD. Because Iran is located on the Alpide seismic belt and due to the presence of many faults in the region, as well as the historical, cultural, and tourism importance of the tower, examining the behavior of this structure under earthquake conditions is an important matter. To investigate the performance of the tower under various earthquake loadings, this study uses the finite-element method and nonlinear dynamic analysis as well as field and experimental tests to determine the mechanical properties of masonry blocks and the soil around the building. Accordingly, after the modeling of the tower and the surrounding soil, modal analysis, as well as static and time history analysis, was carried out under seismic records with different frequency contents. The results showed that the records with low frequency contents produced higher displacements and stresses in the tower, such that Tabasrecord, with high frequency content, and Loma-Yerba earthquake, with low frequency content, produced the maximum displacements of 13.88 and 27.57 cm, respectively. Stress contours resulting from the earthquake records in all cases exceeded the compressive and tensile strength of the tower's materials, which indicate the necessity of seismic rehabilitation.