Finite Element Thrust Line Analysis (FETLA) Based Sensitivity Analysis of the Thrust Line of a Masonry Dome with Tension Rings

Ancient masonry dome structures were designed by master builders using simple geometrical rules, which are similar to the graphical thrust line approach. Most of these masonry domes were designed as a series of arches. Such simplification fails to incorporate the effects of hoop forces. As a result, almost every ancient masonry dome happens to exist with vertical cracks due to hoop tension. Tension rings are used to enhance the capacity of these masonry domes by imparting hoop tension resistance. Design of tension rings requires the assessment of the forces in dome masonry and tension rings. The graphical thrust line based analysis fails to incorporate the effect of hoop forces on the dome stability and hence it cannot be used for analysing domes with tension rings. On the other hand, discretisation-based methods of analysis, like the finite element method, requires precise information on material properties of the masonry dome for its stability study. In this paper, the sensitivity of the analysis results – to the mechanical properties of the dome and ring materials adopted – is studied using the Finite Element Thrust Line Analysis (FETLA). It is found that ring-strengthened masonry domes can be analysed using this analysis method, without the need for an accurate assessment of mechanical properties of the masonry.