System identification of elevated steel water tank using ambient vibration test and validation of numerical model

The present research aims to investigate the feasibility of using ambient vibration tests for system identification of elevated water tank. To this end, the elevated water tank located in TMU campus is utilized. The tank is instrumented with a sensitive velocimeter sensor and the ambient velocity of the tank is recorded for 30 minutes in three perpendicular axes. The amplitude of the velocity signal reaches to about 30 mm/s. using the peak picking method, the fundamental frequency of the tank is determined about 1.9 Hz. Although, considering the non-perfect symmetry of the tank and the misaligned orientation of the sensor the obtained values in two lateral directions differ 5%. Then, the numerical model of the tank is prepared in software and calibrated. In the primary modeling, the values of natural frequencies of the tank are in good agreement with the results of the ambient vibration data. It shows the calibration of the numerical model which can be used in the assessment of the seismic behavior of the elevated water tank.