Comparison of soil-structure interaction obtained from spectral ratio methods applied to earthquake and microtremor records

Installing strong ground motion measuring devices in existing structures is significant for earthquake engineering and building safety to monitor whether the structures can be damaged or not. This study determined with different spectral ratio methods the dominant vibration period and amplification characteristics of both the structure and the ground from earthquake and noise records and compared the results. For this purpose, online-monitored accelerometer devices were placed on the top floor of a 5-story public building that was improved in 2008, on the ground where it was built, and on the rock approximately 1 km away from this building. MASW measurement was taken to determine the ground class of the area where the accelerometer device was installed on the ground right next to the building. Many earthquake records of different distances and magnitudes were obtained by the fixed devices located in the building, on the ground, and the rock. Spectral ratio methods were applied to the recorded earthquakes according to the reference station method and horizontal/vertical ratio methods according to the single station method. In addition to the analyses applied to the earthquake records, noise measurements were taken at night on the building floors and ground, and these measurements were evaluated according to the horizontal/vertical spectral ratio method and floor spectral ratio methods. As a result of all the analyses, the amplifications, dominant frequencies, and damping ratio of the building and the ground were determined, and the interference status of the building and the ground was examined. As a result, it was observed that the dominant frequency of the building, the spectral ratio amplification, and the damping ratio values of the building were approximately the same by using different spectral ratio methods for earthquake and noise data. In addition, there was a slight increase in the building's dominant period as a result of earthquakes that occurred at different times.