LAYERED SOIL-SYNTHETIC LINER BASE SYSTEM TO ISOLATE BUILDINGS FROM EARTHQUAKES

THE IMPORTANCE OF ASEISMIC DESIGN OF STRUCTURES USING BASE ISOLATION TECHNIQUES IS BECOMING INCREASINGLY EVIDENT TO ARCHITECTS AND STRUCTURAL ENGINEERS. MANY DIFFERENT TYPES OF BASE ISOLATORS, GENERALLY COMPLEX MECHANICAL SYSTEMS WHICH REQUIRE AN EXTRA FLOOR BENEATH THE BUILDING, HAVE BEEN PROPOSED TO DATE. EXISTING ISOLATION SYSTEMS ARE EITHER OF A PURE-FRICTION OR FLEXIBLE TYPE, OR A COMBINATIONOF THE TWO. THEY REDUCE EARTHQUAKE-INDUCED LATERAL INERTIAL FORCES ON STRUCTURES THROUGH LIMITING FRICTION EFFECTS AND/OR LENGTHENING THE NATURAL PERIOD OF VIBRATION OF THE TOTAL SYSTEM. FRICTIONAL PROPERTIES ARE USUALLY PROVIDED USING STACKED TEFLON-COATED STEEL PLATES, WHILE FLEXIBILITY IS PROVIDED BY ELASTOMERIC RUBBER PADS. A NEW BASE ISOLATION SYSTEM COMPRISED OF ALTERNATE GEOSYNTHETIC LINERS AND SOIL LAYERS IS PROPOSED TO BE EVALUATED AND IMPLEMENTED. GEOMEMBRANE AND GEOTEXTILE GEOSYNTHETICS TYPICALLY HAVE VERY LOW FRICTION COEFFICIENTS. A LAYERED GEOTEXTILE/GEOMEMBRANE-SOIL SYSTEM PROVIDES A PRACTICAL, LOW-COST, AND SIMPLE-TO-INSTALL BASE ISOLATION SYSTEM THROUGH LOW FRICTIONAL PROPERTIES OF GEOSYNTHETICS AND THE FLEXBILITY OF A SOIL LAYER. LATERAL DEFLECTION OF STRUCTURES MAY BE LIMITED BY HYSTERETIC DAMPING OF THE SOIL LAYER AND BY SOFT BACKFILL MATERIALS AROUND THE BUILDING BASEMENT. THE EXPERIMENTAL AND ANALYTICAL STUDIES PROPOSED WILL VERIFY THE EFFECTIVENESS AND EFFICIENCY OF THE PROPOSED SYSTEM.