Seismic assessment by numerical analyses and shaking table tests for complex masonry structures: the Hagia Irene case study

The Church of Hagia Irene is located in Istanbul very near to the Hagia Sophia Basilica, and it was the ???Cathedral??? of Bisanzio ??? Constantinople before the building of Hagia Sophia by Costantino. The study of Hagia Irene is part of a program about ???Seismic Evaluation and Retrofit of Historic Buildings??? regarding many monuments of Istanbul and carried out by the Turkish Ministry of Culture. The seismic assessment of Hagia Irene is studied through historical analyses, direct investigations on the materials, survey of the present conditions and damages derived by past earthquakes, numerical analyses and shaking table tests on a scaled model. The scale tests were carried out in the ENEA-Casaccia Research Centre in Rome . The final goal of the experimentation was been the evaluation of the seismic strength of Hagia Irene with and without reinforcement. The comparison between the results of the scale tests and the ones coming from the FEM modelling also allowed to make interesting considerations about the reliability of both the structural models. The tests were arranged into two different phases. In phase 1, the scale model was subject to different time-histories of acceleration having increasing of intensity amplitudes, up to an intensity level characterized by significant structural damages. Phase 2, carried out on the reinforced model, allowed to assess the effectiveness of the consolidation works foreseen for Hagia Irene. For the implementation of the scale model of the church, a scale factor equal to 1:10 was chosen in such a way to better fulfil the shaking table dimensions and capability. Because the in situ survey and the numerical global models show as Hagia Irene is structurally weaker for seismic actions in its transversal direction, the scaled model and the shaking table test were designed for the transversal actions only. Thus, also in Phase 2 the intervention were mainly designed for an horizontal shear reinforcement at the intermediate level of the gallery floor and at the roof level, in such a way to improve the global structural collaboration respect the transversal actions. Together with a system of accelerometers placed on the scaled model, a cluster of high resolution (up to 4MPixel) Infrared Cameras has been used to measure accurate 3-D positions of many markers placed on the model. This innovative monitoring technique allowed the measure of the 3 axial absolute displacements with high accuracy and the possibility to link the 3D-motion time histories of the tracked markers with CAD drawings of the structure, in such a way to also compare and validate the Finite Element model responses.