Influence of isolation system characteristic strength on the earthquake behavior of base-isolated liquid storage tanks

346-352Earthquake performance of liquid storage tanks may be substantially improved by base-isolation. However, the possibility of facing large isolator displacements in case of large magnitude near-fault earthquakes threatens the safety of these structures, which may be realized if the period of the velocity pulses that typically exist in the near-fault earthquake records are close to their isolation periods. Increasing isolation system characteristic strength may help reducing the aforementioned large isolator displacements but this in turn may have a negative impact on the superstructure response. Therefore, this study aims to investigate the influence of the characteristic strength of the isolation system on the behavior of base-isolated liquid storage tanks under representative historical near-fault and far-fault earthquakes by making use of a set of benchmark tank models with different levels of isolation system characteristic strength ratios. Numerical modeling and non-linear time history analyses are carried out via the academic software 3DBASIS-ME,which offers the possibility of conducting such modeling and analysis following a highly preferred mechanical analog that is able to take the deformability of the tank wall and sloshing of the fluid into account by considering the fundamental sloshing and fundamental fluid-tank modes of vibration as single degree of freedom systems sharing a common isolation base-mat. The seismic responses including isolation system displacement, sloshing fluid displacement, isolation system shear force, fluid-tank shear force, and sloshing fluid shear force are reported in a comparative manner. Results show that while higher characteristic strength effectively reduces large base displacements observed under near-fault earthquakes, it may cause significant amplifications in the superstructure responses particularly under far-fault earthquakes

Behavior of base-isolated liquid storage tanks under synthetic near-fault earthquake pulses

Protection of liquid storage tanks from earthquake hazards is vital as damaging of these structures may result in significant economic losses. Base isolation has emerged as a successful alternative to classical earthquake resistant design of liquid storage tanks. However, near-fault earthquake records may include velocity pulses with long periods and large amplitudes that may cause large seismic responses since the isolation periods of base-isolated liquid storage tanks encompass a similar range with pulse periods of near-fault earthquakes. In order to assess the influence of near-fault earthquakes on the seismic response parameters, here, the behavior of a benchmark base-isolated liquid storage tank is evaluated under synthetically generated pulses which represent near-fault earthquakes of different magnitudes recorded at different fault-distances. Seismic response parameters including base and sloshing fluid displacements, isolation system shear, fluid-tank shear force, and fluid shear force are reported in a comparative manner

Isolated giant intrathoracic meningocele associated with vertebral corpus deformity

Published reports of intrathoracic meningocele with vertebral corpus defects in the absence of neurofibromatosis are very rare. We report a 9-year-old male with intrathoracic meningocele. We believe that vertebral corpus defects may play a certain role in the etiology of intrathoracic meningocele. © 2004 Elsevier B.V. All rights reserved