Evaluation of Seismic Behaviour of Ferrocement Elevated Water Tanks by Using Ambient Vibrations Tests

In this study a series of ambient vibration tests on the triple ferrocement elevated water tanks with 150 cubic meters volume, is carried out. In order to verify the dynamic characteristics of full, half-full and one full tanks (mass eccentric system), the different arrangements of sensors are used. The effects of base rotation are also considered in the tests. Natural frequencies and mode shapes obtained from tests are compared to the mathematical model of the tanks using finite element method. In order to verify the effect of different assumptions on the design forces, the revised mathematical model is analyzed by spectral method. The results indicate that base rotation causes the change of design forces especially in the vicinity of the base of system.