Forensic Estimation of Uplift of an Anchored Tank During the 2011 Earthquake Off the Pacific Coast of Tohoku

The reconnaissance just after the 2011 earthquake off the Pacific coast of Tohoku reported the pulling out of anchor bolts of an upright cylindrical tank. Regarding the tank as an unanchored tank and employing the accelerogram recorded at 2 km off the tank, uplift of the unanchored tank during the 2011 earthquake off the Pacific coast of Tohoku was forensically examined. The time history of the uplift displacement of the tank computed by the explicit finite element analysis reveals that the unanchored tank uplifts during the earthquake and its uplift displacement is more than the length of the pulling out of the anchor bolts found by the reconnaissance. This implicitly corroborates applicability of the explicit finite element analysis to analyzing the tank rocking behavior. In addition to that, the uplift displacement of the unanchored tank was estimated by some calculation methods available to date and compared with that computed by the explicit finite element analysis. Comparison reveals that the calculation methods used herein may likely overestimate the uplift displacement of the unanchored tank and need to improve their calculation accuracy.