Determination of Buildings Period and Vulnerability Index Using Microtremor Measurements

Microremor data has an important role on determining the ground dominant periods. Another way of use of the method is the application on the constructed buildings for investigating the strength and periods of each floor. It is possible to define the period of each floor and calculate the floor spectral ratio (FSR) parameter using microtremor data. This parameter is being used to estimate the transfer function (amplification, natural frequency and vulnerability index) of the buildings. In this study, microtremor data were collected in Folkart Towers which have a length of 200 m. The data were recorded at 14 floors for 40 minutes. The validation of frequencies were determined using FSR in order to obtain damping ratios accurately. The variation range and tendency between damping ratio and frequency of each floor with damping ratios and vulnerability indices, along with the preliminary influence factor, were presented and discussed. In addition, a fitting curve was plotted indicating the relation between the damping ratio and dominant natural frequencies of the floors. Furthermore, evaluation of strength, damping ratio, natural dominant frequency and vulnerability index of the building were estimated by interpreting microtremor data. The dominant frequencies of 44th, 22nd and 7th floors of the buildings were calculated as 0.4 Hz, 0.4 Hz–1Hz and 1.1 Hz respectively. It was determined that the buldings have 2 dominant periods. They are 1.1 Hz from 1st to 22nd floors and 0.4 Hz from 23 to 44th floors.