Seismic response of elevated steel tanks equipped with the seesaw system.

Aim of this paper is to investigate the effectiveness of the seesaw system in mitigating the seismic response of elevated steel tanks for water storage. This is accomplished by conducting a number of non-linear time-history (NLTH) analyses to a specific in terms of shape and water storage capacity elevated steel tank. To conduct the NLTH analyses: (i) the two (horizontal) or the three (two horizontal and one vertical) translational components of the seismic motions are utilized; (ii) two different water heights are considered, representing the cases of a partially-filled and an almost filled tank; (iii) the tank is assumed founded either on a rigid or on a flexible ground, permitting, thus, an assessment of the influence of soil-structure interaction (SSI). The NLTH analyses are performed first for the tank without the seesaw system and then with it. The response metrics to be compared are the drift and residual drift ratio of the tank, the axial and shear stresses exerted to the shell of tank, the maximum forces developed to the members of the seesaw system as well as the formation of plastic hinges to the steel framing system that supports the tank. Interpretation of the results provided by the aforementioned response metrics leads to the conclusion that the effectiveness of the seesaw system to elevated steel tanks of the type studied herein is limited. [ABSTRACT FROM AUTHOR]