Giorgio Croci, Professor of Structural Engineering at « La Sapienza » University of Rome donnera one conférence en anglais pour présenter l’obélisque éthiopien d’Axum.
The Stele has a total height of about 23,50 m, including foundations. The weight is around 152,000 Kg; it was transported in Italy divided into four big blocks, resulting from the collapse due to an earthquake occurred several centuries ago.
The Stele was subsequently reassembled in Rome connecting the pieces with mortar and “bronze” bolts.
The project of dismantlement had to solve delicate problems in order to avoid any damage to the stones. It was therefore decided to separate the blocks along the connecting surfaces by means of a complex system of oil jacks (16 along the vertical direction and 8 along the horizontal direction) connected, using high pressure pipes, to manifolds and to the electric system of pumping.
In order to avoid the direct contact of the steel structure to the stone, the stele had been protected in advance with a layer of fiber-reinforced structural mortar including a structural mesh (in carbon and aramidic
fibers). The control of the applied forces, of the movements at the joint sand of the resulting stresses was achieved by means of a monitoring system which processed in real-time all data coming from the sensors, performed a comparison with design data and, also, with alarm thresholds (excessive inclination, elevated stresses, slippage of stele framework, tension failure of connectors, crushing of compressed edge, etc.).
The blocks of the stele were transported to Axum by an Antonov aircraft (the more suitable of the world for its high load capacity) after several challenges related to the characteristics of the Axum runway were solved (elevated air temperature, reduced length, reduced pressure of the air being the elevation of the site 2500 m over the sea level, etc.).
The reconstruction of the Stele on the original position in the site of Axum is presently in progress. The project foresees the construction of a provisional steel tower in order to lift up the blocks and the subsequent connection between them with carbon fiber bars in order to ensure the necessary strength against seismic actions.
A final restoration and cleaning of the surfaces will complete the works.