Performance of Persian brick masonry discontinuous double-shell domes against earthquakes

Abstract

Abstract Despite the fact that Iran is an earthquake prone country and most of its historical buildings are made of brick masonry that is weak in tension, a large number of domical buildings have been constructed all over the country since many centuries ago. Most of magnificent domes in Iran have survived severe earthquakes. The discontinuous double-shell dome has been widely used for important buildings such as mosques and churches. This type of dome provides the possibility of constructing high and large spaces in order to show magnificence and also accommodate a large number of people inside. In this paper, the structural performance of Persian brick masonry discontinuous double-shell domes against earthquakes has been studied. Different shapes of upper and lower shells have been studied. The domes have had spans of 12 m, 15 m and 18 m and a decreasing thickness from the base to the apex with an optimum apex to base thickness ratio. Domes have been analysed under earthquake load by the non-linear finite element method. The Willam-Warnke failure criterion has been used for brick masonry materials. In addition to parametric study, two existing discontinuous double-shell domes of the Imam mosque and Bedkhem church, and two existing single-shell domes of the Saint Mary church and Saint Stepanos monastery in Isfahan have been studied. The values of maximum stresses have been obtained for these domes. Obtained results indicate that selected earthquakes do not cause the failure of the studied domes. The induced stresses increase by increasing the span. The performance of domes is dependent on the geometrical shape of the upper and lower shells. The dome with a drop four-centred upper shell and a drop elliptical lower shell has the best structural behaviour.