Comparison of the structural behaviour of monolithic and masonry obelisks: Obelisk of Theodosius and Walled Obelisk in Istanbul

•The seismic behaviour of two obelisks in Istanbul was studied.•The obelisk with a stone base is more flexible than the one with a metal base.•The stone base prevents the creation of cracks at the main body of the obelisk.•The metal base increases the flexibility of the obelisk. In this paper, the structural behaviour of the Obelisk of Theodosius and Walled Obelisk, located near the Sultan Ahmed Mosque in Istanbul, is investigated. The Obelisk of Theodosius is made of an integrated and solid red granite that stands on four pieces of bronze cubes and large pieces of stone cubes. The Walled Obelisk is made of small pieces of limestone that stand on only one large piece of stone cube, without bronze cubes. The purpose of this study is the comparison of the structural behaviour of these two obelisks and the effect of their supporting base on their performance under seismic loading. The nonlinear three-dimensional finite element method is used for modelling and the Willam-Warnke failure criterion is adopted for investigation of brittle fracture mechanism. The results of analysis show that the Walled Obelisk is more flexible than the Obelisk of Theodosius. However, the existence of four bronze cubes and four red granite cubes at the corners of the supporting base increases the flexibility of the Obelisk of Theodosius.