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.
damaged, heritage buildings, limit analysis, seismic regions, shallow shell, strengthening
 Krautheimer, R. & Ćurčić, S., Early Christian and Byzantine architecture, Penguin Books Ltd: Harmondsworth, Middlesex, England, 1986.
 Paret, T., Freeman, S., Searer, G., Hachem, M. & Gilmarin, U., Seismic evaluation and strengthening of an historic synagogue using traditional and innovative methods and materials. Proc. 1st European Conference on Earthquake Engineering and Seismology, Geneva, Switzerland, (SD-R) Paper No. 701, 2006.
 Repair and strengthening of historical monuments and buildings in urban nuclei. Building construction under seismic conditions in the Balkan region. NDP/UNIDO Project Rep/79/015, Vienna, 1984.
 Sesigur, H., Celik, O.C., Cili, F., Repair and strengthening of ancient structures. Proc. 1st European Conference on Earthquake Engineering and Seismology, Geneva, Switzerland, Paper No.1387 (SD-R), 2006.
 Rabin, I., Structural Analysis of Historic Buildings: Restoration, Preservation and Adaptive Application for Architects and Engineers, Wiley & Sons: New-York, 2000.
 Danieli (Danielashvili), M., Gabrichidze, G., Goldman, A. & Sulaberidse, O., Experience in restoration and strengthening of stone made ancient domes in seismic regions. Proc. 7th US NCEE, Boston, MA, USA, Vol II: pp. 1167–1175, 2002.
 Jasieńko, J. & Bednarz, Ł.J., Strengthening of historic masonry vaults. Proceedings of the Eighth International Masonry Conference, Dresden, 4–7 July 2010, Vol. 3, eds. Wolfram Jäger, Barry Haseltine, & Anton Fried, Technische Universität Dresden: Dresden, pp. 2131–2140, 2010.
 Jasieńko, J., Bednarz, Ł. & Nowak, T. The effectiveness of strengthening historic brick vaults by contemporary methods. PROHITECH 09. Proc. of the International Conference on Protection of Historical Buildings, Rome, Italy, 21–24 June 2009, Vol.
2, ed. F. M. Mazzolani, CRC Press, pp. 1299–1304, 2009.
 Protection of Historical Buildings, PROHITECH 09, Proc. of the International Conference on Protection of Historical Buildings, Rome, Italy, 21–24 June 2009, Vols 1 & 2, ed. Federico M. Mazzolani, CRC Press, 2009.
 Penelis, G., Karavesiroglou, M., Stylianidis, K. & Leontaridis, D., The Rotunda of Theassaloniki: seismic behavior of Roman and Byzantine structures, Hagia Sophia from the Age of Justinian to the Present, ed. R. Mark & A.Ş. Calmak, Cambridge U niversity Press, pp. 132–157, 1992.
 Poland, C.D. & Reis, E.M., The repair and strengthening of historic Stanford Memorial Church, Tenth World Conference, Balkema: Rotterdam, pp. 5341–5346, 1992.
 Gabrilovich, P. & Richard, P., Methodology for strengthening and repair of earthquake damaged monuments in Pagan, Burma, Proc. of Eight World Conference on Earthq. Engin, San Francisco, USA, Vol. 1, pp. 609–616, 1984.
 Ziyaeifar, M., Meshki, H. & Rajaei, M., Rehabilitation of historical buildings subjected to seismic hazards, a methodology, 13th World Conference on Earthquake Engineering, Vancouver, BC, Canada, Paper No. 1598 (SD-R), 2004.
 Bednarz, Ł., Jasieńko, J., Rutkowski, M. & Nowak, T., Strengthening and long-term monitoring of the structure of an historical church presbytery. Engineering Structures, 81, pp. 62–75, 2014. doi: http://dx.doi.org/10.1016/j.engstruct.2014.09.028
 Pizzetti, G. & Fea, G., Restoration and strengthening of the elliptical dome of Vicoforte Sanctuary. Proc. of the IASS-MSU Int. Symposium, Istanbul, pp. 289–308, 1988.
 Sofronie, R.A., Crisan, R. & Toanchina, M., Retrofitting the masonry of cultural heritage. Fifth National Conference on Earthquake Engineering, Istanbul, Turkey, Paper No. AE-013 (SD-R), 2003.
 Danieli, M. & Bloch, J., Rehabilitation of the religious heritage in seismic regions: principle and practice. Protection of historical buildings. PROHITECH 09. Proc. of the International Conference on Protection of Historical Buildings, Rome, Italy, 21–24 June 2009, Vol. 1, ed. Federico M. Mazzolani, CRC Press, pp. 125–130, 2009.
 Danieli, M. & Bloch, J. Principle, practice and experience of rehabilitation of the historical buildings in seismic regions. Proceedings of the 15th World Conference on Earthquake Engineering (15WCEE), 24–28 September 2012, Lisbon, Portugal, pp. 1–9, Paper No. 392.
 Jasieńko, J., Di Tommaso, A. & Bednarz, Ł., Experimental investigations into collapse of masonry arches reinforced using different compatible technologies. W: Meccanica delle strutture in muratura rinforzate con compositi: modellazione, sperimentazione, progetto, controllo: Atti del 3 Convegno Nazionale, Venezia, 22–24 April 2009, Bologna, Pitagora, pp. 316–324, 2009.
 Krstevska, l., Tashkov, L.J.,Gramatikov, K., Mazozolani, F.M. & Landofo, R. Shaking table test of Mustafa Pasha Mosque model in reduced scale. PROHITECH 09. Proc. of the International Conference on Protection of Historical Buildings, Rome, Italy, 21–24 June 2009, Vol. 2, ed. Federico M. Mazzolani, CRC Press, pp. 1633–1639, 2009.
 Bednarz, Ł., Górski, A., Jasieńko, J. & Rusiński, E., Simulations and analyses of arched brick structures. Automation in Construction, 20(7), pp. 741–754, 2011. doi: http:// dx.doi.org/10.1016/j.autcon.2011.01.005
 Danieli, M. & Aronchik, A., Case study: the strengthening and seismic safety of the Oni synagogue in Georgia. Proc. of the 13th International Conference on Structures under Shock and Impact (SUSI XIII), ed. C.A. Brebbia, WIT Press, pp. 456–466, 2014.
 Akhvlediani, N., Design of reinforced concrete domes by the method of limit equilibrium, Studies of the Theory of Structures Issue 10, Gosstroiizdat: Moscow, pp. 127–132, 1961. doi: http://dx.doi.org/10.2495/susi140391
 Akhvlediani, N. & Danielasvili, M., Limit analysis of reinforced concrete shells, Archiwum Inz. Lądowey, 36(3), pp. 187–205, 1990.
 Shugaev, V., Engineering Methods in Nonlinear Theory of Limit Equilibrium of Shells, Gotik: Moscow, 2002.
 Gabrichidze, G. (ed.), Engineering Analysis of the Racha Earthquake Consequences in Georgia 1991, Metsniereba: Tbilisi, GA, 1996.
 Danielashvili, M., Synagogue in Oni. Engineering Analysis of the Racha Earthquake Consequences in Georgia 1991, Metsniereba: Tbilisi, GA, 1996.
 Sekhniashvili, E.A., Danielasvili, M.A. & Zhorzholadze, T.A., Instruction for Investigating the Technical Conditions and Seismic Stability of Civil and Public Buildings in Georgia. Ministry of Architecture and Building, Academy of Sciences of Georgia: Tbilisi, GA, 1992 (in Georgian).
 Danielasvili, M.A. & Tchatchava, T.N., A method for quantitative estimation of the earthquake resistance of buildings. Earthquake Engineering, 1, pp. 14–16, 1999 (in Russian).
 Danieli, M. & Bloch, J., Evaluation of Earthquake Resistance of Existing Reinforced Concrete Buildings, Ariel University: Ariel, pp. 192, 2014.
 Danieli (Danielashvili), M. & Bloch, J., Evaluation of earthquake resistance and the strengthening of buildings damaged by earthquake. Proc. 1st European Conference on Earthquake Engineering and Seismology, Geneva, Switzerland, Paper No. 673 (SD-R), 2006.
 Levin, M.S. & Danieli, M.A., Hierarchical decision making framework for evaluation and improvement of composite systems (example for building), Informatica, 16(2), pp. 213–240, 2005.
 Danielashvili, M., Gabrichidze, G., Melashvili, Y. & Sulaberidze O., Study of some reinforced and metal spatial structures in seismic regions of Georgia. Proc ICSS-98, Vol. 1, Moscow, pp. 396–403, 1998.
 Instruction manual on design of the reinforced concrete space coverings and floor structures, (in Russian). Stroiizdat: Moscow, 1979.
 Danieli, M., Aronchik, A. & Bloch, J., An original method for strengthening ancient stone domes in seismic regions and solving corresponding problems of stress–strain state analysis. IJRET: International Journal of Research in Engineering and Technology, 3(10), pp. 1–15, 2014, available http://www.ijret.org. doi: http://dx.doi.org/10.15623/ ijret.2014.0310001