Numerical Modelling of Masonry to Explore the Performance of Anchor Based Repair Systems and the Repair of Monuments in Cairo

This paper is in two parts; firstly a method of numerical modelling is described that is being used to investigate the performance of masonry strengthening; secondly how more pragmatic approaches are being used for localised masonry repairs with examples taken from the Mosque of al Ghuri, Cairo. Numerical modelling based on a discrete element formulation has been employed to simulate the response of masonry to seismic loading. Using dynamic non-linear numerical analysis the performance of shear walls with and without retrofitted strengthening has been compared. Models representative of ashlar masonry laid with a weak lime-based mortar have been investigated. The benefits of strengthening by the introduction of passively stressed reinforcement are predicted for various arrangements when subjected to seismic loading. The reinforcement is represented explicitly in the analysis allowing direct assessment of damage and potential failure mechanisms. It is concluded that, although more work is required to verify simulations against tests and field experiences, the discrete element technique is ideally suited to dynamic masonry simulation and overcomes many difficulties experienced with traditional finite element analysis. The overall performance of masonry acting compositely with retrofitted reinforcement has been predicted and comparisons made between different reinforcement dispositions. It has also been shown that unless carefully placed additional reinforcement may actually reduce seismic resistivity. Gifford and Partners have been assisting with the conservation of the monuments of Cairo since the earthquake (5.9 on the Richter scale) in 1992. Recently repairs have been completed to the mosque of Al Ghuri. These works are described.