Case History: The Mosque of al-Ghuri, Egypt

Case History: The Mosque of al-Ghuri, Egypt

It has to be accepted that all representations of masonry structures through numerical modelling will inevitably present a somewhat idealised representation. In practice, a degree of pragmatism and engineering judgement is required, especially where localised repairs are involved. The reinforcement of Al Ghuri Mosque in Cairo - Egypt, is a case in point.

In 1992 an earthquake of approximately 5.9 on the Richter scale occurred 30km to the south-west of Cairo. The focal depth was near the surface and its relatively high frequency meant that damage to low structures of up to five storeys was intensified. Built in 1504AD (909AH) the mosque of Sultan al-Ghuri was left in a very delicate state of equilibrium. Despite having survived for 500 years, earthquakes and neglect had brought the structure to the point of collapse. Typical damage included separation of walls at right angles resulting in vertical cracks, spreading of the arches and dropping of voussoirs, settlement of the floors, failure of roof to wall connections and a loss of integrity of the walls construction.

A five metre (16' 5") long vertical
anchor being installed at roof level.

An archway is computer modelled to evaluate potential seismic loading.

Cintec anchors were extensively introduced to restore structural integrity and provide additional ductility to the building. Anchors up to 12 metres long served to stiffen individual walls which were usually comprised of two facing skins filled with a core rubble. Longitudinal ties in each of the stone facings in the walls above arches serve to resist the thrusts naturally produced by the arch as well as serving to assist the walls to resist subsequent earthquakes.

In addition, transverse ties of length equal to the thickness of the wall acted as consolidation anchors. Furthermore, Cintec anchors connecting the roof structure to the perimeter walls are intended to create a diaphragm action.

Our engineers drawing details typical
anchor placement for the arches and sidela walls.

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