Conservation of a slender historical Mamluk-style minaret by passive control techniques

Abstract

During the Egypt/Dahshur 1992 earthquake, a large number of historical Islamic minarets, especially those built during the Mamluk era, were significantly damaged. The level of damage in Mamluk-style minarets was assigned to their massive size, and their irregular distribution of mass and stiffness along their heights. In this paper, the seismic vulnerability of a representative Mamluk-style minaret, namely Manjaq Al-Yusufi (1349 A.D.) is investigated and some seismic protection techniques are proposed and evaluated. Geometrical, material, and geotechnical data were determined at the site. A realistic three-dimensional finite element model of the minaret that reflects those properties was constructed. Ambient vibration tests were then performed on the minaret, and its modal parameters such as fundamental periods and mode shapes were obtained. The ambient vibration test results were then used to update the finite element model. The seismic hazard at the minaret location was evaluated, and a seismic risk study of the minaret was performed with the conclusion that the minarets will be highly vulnerable during moderate earthquakes. A seismic protection technique that includes the use of high damping rubber bearings HDRB and vertical steel anchoring bars is proposed and evaluated. The proposed technique was found to efficiently reduce the seismic risk of the minaret under investigation. Copyright © 2004 John Wiley & Sons, Ltd.