OPTIMIZING THE DYNAMIC PERFORMANCE OF FRICTION PENDULUM ISOLATORS IN LIQUID FUELS TANKS Alexandros TSIPIANITIS 1 , Yiannis TSOMPANAKIS 2 * ABSTRACT Large-scale liquid storage tanks are used worldwide for storing chemicals, liquefied natural gas (LNG) and oil. Any possible damage from man-made or natural hazards, such as earthquakes, to these critical infrastructures would cause serious problems and devastating consequences. Moreover, they should remain functional even after a severe earthquake to support restoration, thus, their reliable seismic design is mandatory. Nevertheless, their seismic performance assessment is quite complex, mainly due to the hydrodynamic interaction with their liquid content. For this reason, base isolation is generally considered as a highly efficient technique for the seismic protection of liquid storage tanks. The aim of any base isolation scheme is to decouple the superstructure from the imposed ground motions, providing flexibility in the horizontal axes and sufficient rigidity in the vertical axis to accommodate the structural weight. Various types of such devices have been installed in storage tanks in order to achieve best possible seismic isolation. Elastomeric bearings, such as lead-rubber bearings (LRB), high damping rubber bearings (HDRB) and frictional bearings, such as single friction pendulum bearings (SFPB), double friction pendulum bearings (DFPB) and triple friction pendulum bearings (TFPB) have been used. In this work, the optimization of the main parameters of SFPB is considered. In particular, genetic algorithms (GA) are used to derive friction coefficient and radius of curvature values that optimize the performance of SFPB isolators applied in the base of tanks of both squat and slender geometry. The objective is to minimize the imposed ground accelerations at the base of the tanks, while constraints related to damping and period are used. Keywords: Liquid storage tanks; base-isolation; surrogate models; dynamic response; optimization. 1. INTRODUCTION Liquid storage tanks are used for the safe storage of hazardous chemicals, fuels (liquefied natural gas (LNG), oil) and water. During an earthquake they exhibit a quite different dynamic behavior compared to buildings and bridges due to the hydrodynamic interaction with the liquid content, i.e., they are subjected to inertial loads and hydrodynamic pressures. This behavior was represented by the mechanical analogue of Housner (1963), dividing the hydrodynamic response of the tank-liquid system in two uncoupled components: the impulsive component (i.e., the lower part of the liquid content that moves in unison with the tank walls) and the convective component (i.e., the upper part which is related to sloshing motion). Note that an additional complexity to assess their seismic behavior occurs in the presence of a soft foundation layer due to the resulting dynamic soil-structure interaction. 1 PhD Candidate, School of Environmental Engineering, Technical University of Crete, Greece, altsipianitis@gmail.com 2 Associate Professor, School of Environmental Engineering, Technical University of Crete, Greece, jt@science.tuc.gr