Armen Assatourians - Earthquake Engineering Research Consultant, Yerevan, Armenia
Sohrab Fallahi - Senior Structural Designer, E.S.S. Consulting Eng. Co., Tehran, Iran
Mohammad Reza Mehrdoust - Earthquake Engineer, Building and Housing Research Center (BHRC), Mashhad, Iran

Water Tanks are amongst the most important special structures which are used for storage and providing the needed water on the pick usage time in water supply networks. According to this, investigating the seismic behavior of these structures are of much importance. In current research, the seismic response of circular steel water tanks with low and medium H/D ratio is studied, using Lagrangian approach for considering the fluid-structure interaction. Analysis procedure of the whole water-tank system is completed by the means of Time History Analysis method, using 5 pairs of horizontal components of selected accelerograms, recorded on soil categories of Rock, Dense Soil, Loose Soil and Very Loose Soil, scaled to spectral acceleration level of Sa=0.35g. The response is computed for the filling strategy of Empty, 50% Full and 100% Full conditions of both shapes.

Steel Water Tanks, Lagrangian Approach, Spectral Acceleration, Time History Analysis, Accelerograms