Seismic Isolation Using a Geosynthetic Liner. Shaking Table Tests Applied To a Semi-Real Scale Storage Tank

Abstract eng:
Within the last 20 years, seismic isolation systems and seismic protection devices have had an outstanding performance during major earthquakes providing many structures with operational continuity and lowering the probability of undergoing large damage after severe ground shaking. Likewise, seismic isolation systems are able to keep the content of the buildings reasonably intact by means of energy dissipation mechanisms, i.e., elasto-plastic deformation, damping, friction, etc. Based on the principle of friction, seismic isolation with geosynthetics uses a controlled sliding surface along an interface liner to dissipate energy input from an earthquake. An experimental analysis of a seismic isolation system using geosynthethics is introduced. A high strength, non-woven geotextile placed over an ultrahigh molecular weight polyethylene (geotextile/UHMWPE interface) constitutes a synthetic liner that can provide seismic protection throughout energy dissipation by means of slip deformations. A series of shaking table tests applied to a semi-real scale storage tank were carried out. The dynamic response of the system isolation-liquid-tank is registered and studied in a semi-real scale. Instrumentation consisting of LVDT’s, accelerometers and pressure transducers were placed at specific points of interests at the storage tank as well as at the shaking table to measure accelerations, displacements and water pressures. During each test, time histories of acceleration, displacements and water pressures were recorded, i.e., transmitted accelerations from the table to the tank, relative displacements of the tank with respect to the table and water pressures at the tank’s inner wall. Both, harmonic and 2D earthquake excitations (bidirectional simultaneously) were used to analyze the dynamic response of the system tank-liquid-isolation and to prove the seismic performance of the interface as seismic isolation. One of the main results from the shaking table tests was a remarkable reduction of transmitted accelerations from the shaking table to the tank (verified for all tests). In addition, for the isolated condition, lower water pressures at the tank’s inner wall were measured during dynamic excitation in comparison to those measured for a fixed-base condition (no isolation). One of the benefits of using geosynthetics as a seismic isolation is when threshold acceleration is exceeded, which limits the maximum acceleration transmitted to the superstructure from the excitation. Also, lower levels of seismic demand produces lower values of seismic output parameters i.e., base shear, seismic overturning moments, sloshing effects and water pressures. This experimental research demonstrates the technical feasibility of using an interface of geosynthetics as a seismic protection system, and shows its advantages to be used in earthquake hazard mitigation.

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