An example for determining the cause of damage in historical buildings: Little hagia sophia (Church of St. Sergius and Bacchus) – Istanbul, Turkey

The Church of St. Sergius and Bacchus, built during 527–536 AD in times of Justinian Regina, is examined in this study. The structure has been damaged and contains many cracks due to external influences and earthquakes. It is crucial to determine the current condition of the structure and causes of damage for its restoration and endurance. Material tests have been performed; measured drawings were prepared; the location and shape of the damage status were determined; local ground conditions were detected; and finally a 3D model of the structure was assembled together to achieve this goal. The building was modeled and analyzed with finite elements method in order to spot the effects that caused damage. The calculations took the values for external loads, and earthquake, and bearing movements into consideration. Linear and non-linear analyses of the structure for every loading condition were realized as well. The cracks detected on the building and the cracks estimated through geometrical non-linear calculations on condition of bearing movements as the result matched perfectly. The findings at the structure also supported the view that there occurred bearing movement. Restoration and strengthening of St. Sergius and Bacchus have been initiated under the light of these findings.