Structural system identification of elevated steel water tank using ambient vibration test and calibration of numerical model

The present research aims to investigate the feasibility of using velocity ambient vibration tests for system identification of an elevated water tank. To carry out the experimental study, an elevated water tank located in Tarbiat Modares University (TMU) campus is utilised. The tank is instrumented with a sensitive velocimeter sensor (microtremor), 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. Employing the peak-picking signal processing method, the fundamental frequency of the tank is determined about 1.9 Hz. Although, considering the non-perfect symmetry of the elevated tank structure and the misaligned orientation of the sensor, the obtained values in the two lateral directions differ 5%. Then, the numerical model of the tank is prepared and calibrated using matrix structural analysis. 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.