An Experimental Study on Geosynthetics as Base Isolators Ashish Kumar Chaudhary PG Student, Department of Civil Engineering, NIT Silchar, Silchar 788010, India Satyabrata Choudhury Professor, Department of Civil Engineering, NIT Silchar,Silchar 788010, India Abstract - Base isolation is a technique used for mitigating seismic response of structures, which has now been around for a while, but not much popular due to its higher cost. However, the technique has been applied in state of the art buildings. Base isolation is achieved by deliberately increasing the time period of the structure. The present study is aimed at assessing the validity of geotextile as base isolator and its application as an isolator in mitigating the response of an RC Frame building model. Geosynthetic isolator is a friction isolator. The one-fourth scaled 2-storey three dimensional RC frame model is assessed under various earthquake simulated conditions using shake table. The results show that the geosynthetics can be used effectively as base isolator. The level of peak floor acceleration in the fixed base condition is about 1.3 to 1.9 time of the similar observed acceleration in isolated conditions, while the level of acceleration at the base level is about 0.52 to 0.77 time of the acceleration at the table level in isolated conditions. Keywords: Friction Isolator; Geosynthetic; Shake Table; Three Dimensional RC Frame Model. 1. INTRODUCTION In recent years base isolation has becomepopular structural design technique for buildings and bridges in highly seismic areas. Many types of structures have been built using this approach, and many others are in the design phase or under construction. Most of the completed buildings and those under construction use rubber isolation bearings in some way in the isolation system. But the techniques are quite expensive for lower budgets project and if traditional base isolators are to be equipped on the small projects then, sometimes it could over run the cost of the overall project. Therefore, it provides a scope of research for cheaper base isolators for small scale projects. In this paper the use of geosynthetics as a base isolators has been tried to be implemented on the scaled model of RC Frame structure to see its effectiveness. Here, the sliding friction isolator was used, with one geosynthetics layer attached to the base of the first storey column and other to the plinth level of the substructure. In the frictional base isolators the base filter out earthquake force via the discontinuous sliding interface between which the force transmitted to the superstructure are limited by the maximum frictional forces regardless of earthquake intensity. 2. EXPERIMENTAL PROGRAM The shake-table experiments were carried out with a one- fourth scaled RC Frame building model with and without base isolation. The materials used in the model are M20 concrete, Fe415 and Fe250 rebar. The structure is isolated from the foundation using Non-Woven polypropylene geotextile GSM 180 as isolators. The building model has been subjected to harmonic excitation using geotextile using shake table. A series of dynamic tests have been conducted under different frequency inputs. Fig. 1. Schematic Diagram of the Shake Table Test setup. Vol. 5 Issue 02, February-2016 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 http://www.ijert.org IJERTV5IS020564 (This work is licensed under a Creative Commons Attribution 4.0 International License.) Published by : 690