EXPERIMENTAL DETERMINATION OF THE NATURAL FREQUENCY OF VIBRATION OF ST. STEPHANOS CHURCH USING AMBIENT VIBRATIONS

The historical buildings are valuable symbols demonstrating the history of every nations. These structures should be safe against future earthquakes. For keeping safe of historical buildings against earthquakes disaster, seismic behavior study including their vulnerability assessment, strengthening and improvement is essential. In this study, we evaluated St. Stepanos church building to determine the natural frequencies in different parts of it. This church is located in Jolfa city in the north-west of Iran. Generally, seven records were recorded in the St. Stepanos church that just three records including the northern and eastern walls around of church and the Bell Tower building were used and the others were passed up because of having the excessive noise.The microtremor data were analyzed using two methods. The first was J-SESAME software and the second was four-spectral method. The data were processed based on concept of transfer function and horizontal-to-horizontal spectral ratio in the both methods and finally the results of them were compared.Thus, the average natural frequency of walls around of the church is obtained 5.48 Hz (J-SESAME software) and 5.37 Hz (four-spectral method) for the walls around of the church in their weak direction. Also for the Bell Tower building, 9.45 Hz (J-SESAME software) and 9.17 Hz (four-spectral method) in NS direction and 7.17 Hz (J-SESAME software) and 7.17 Hz (four-spectral method) in EW direction. The results show that the frequencies obtained from the two methods are very close and are reliable methods for determining the vibration frequency of structures

کلیدواژه ها:

St. Stepanos church ، Natural frequency ، Microtremor ، J-SESAME software ، Four-spectral method