Securing the safety of heritage buildings in active seismic regions

This article describes the principles and actual procedures of restoration and strengthening of heritage buildings that have been applied in mountainous regions of Caucasus, in Georgia. The buildings in question are the 11th century temple in Nikortsminda and the 19th century synagogue in Oni, both damaged by an earthquake in 1991. This article presents examples of conservation of these two structures and refers to a conservation project for the 18th century mosque in Akhaltsikhe. As to the Nikortsminda temple, temporary conservation was applied prior to an expected aftershock period. Its permanent conservation was completed 2 years later. In all three cases, the design was aimed at preservation of initial geometry and appearance by creating composite (stone reinforced concrete) structures, which were partially or fully hidden. It is worth mentioning that both the temple in Nikortsminda and the synagogue in Oni survived the Richter magnitude 6.2 earthquake in this region on September 8, 2009, without any substantial damage caused. The causes of deformation and loss of stability of thin shallow shell of the same type are analyzed; the example of strengthening and safeguarding the shell of this type is given. The method used for the shell strengthening was assumed as a basis for developing the method of strengthening ancient stone domes. The authors believe that design principles applied in these projects can provide substantial contribution to successful conservation of much larger projects, along with the increase in their earthquake resistance.