Applicability of the Simplified Analysis and Relevant Calculations to Evaluating Uplift Displacement of Unanchored Tanks

Abstract

Evaluation of the rocking motion of unanchored cylindrical tanks subjected to the ground acceleration is a main topic in the framework of the seismic vulnerability assessment of this particular kind of structures. However, despite the anchored or unanchored tanks, any calculation that attempts fully evaluate tank uplift has not been presented, while many of the analyses of the tank rocking motion and the deformation of the tank bottom plate have been respectively presented. This paper carries out a thought experiment of applicability of these analyses to evaluating uplift of the unanchored tanks. First, this paper focuses on an anchored tank at a chemical plant whose anchor bolts were pulled-out during the 2011 off the pacific coast of Tohoku Earthquake. Second, combine a few analyses of uplift of the unanchored tanks being available to date; then, calculate the uplift displacement of an anchored tank of interest as if it were an unanchored tank. Next, infer the pulling-out length of anchor bolt of the anchored tank of interest from a photo in a reconnaissance report; then, compare it with the uplift displacement calculated. Since the uplift displacement calculated is larger than that inferred. Since a discrepancy between them would be responsible for the constraint effects of anchors that have not been clearly quantified, the present analyses of the tank rocking motion and the deformation of the tank bottom plate may have a potential to give an appropriate uplift of unanchored tanks.