Enhancement of Seismic Performance of RC Frame Structure Through Base Isolators

Abstract

With the onset of earthquakes occurring all over the world, the society finds it justifiable that the structural engineers make the structures withstand the earthquakes. In the whole conventional design approach a single thought process is common: Capacity > Demand. With the uncertainty in the earthquake forces, the demand is taken into account and the designers have to make sure that the capacity exceeds the demand for a stable structure. In places of high seismicity, the strength of building, capacity, has to be relatively increased to withstand the structural damage. But it’s not quite practice to increase the capacity indefinitely. This study highlights the role of Base Isolation in enhancing the seismic performance of the structure relative to a fixed base structure. A G+4 story fixed base structure is modelled on ETABS. Time History of 2005 Earthquake which was recorded in Abbottabad region is applied. The structure is analysed and the loads are taken into account. Software is coded to design a Base Isolator using Visual Basic Studio and the language adopted is C#. The values are extracted from the E-Tabs file and inputted in the software. The software runs its functions and gives the final Design of the Base Isolator. On the account of the final design, the software directs the user towards available isolators provided by the company with their contact details. Hand Calculations are done to verify the software’s authenticity. Upon verifying the design results of the software, the designed base isolator is modelled on ETABS for a comparative study between a fixed base structure and an isolated one. The results are compared and the effectiveness of base isolation is found in enhancing the seismic performance of a structure. Base isolation basically reduces the demand forces by shifting the time period of the structure. The displacement can be controlled by introducing additional damping in the structural system, which also helps in reduction of the demand forces. In this study detailed literature review has been carried out on the subject. Design considerations of base isolator as well as base isolated building has been presented after application of time history of Abbottabad earthquake 2005. Detailed design of LRB isolators has been carried out using a program developed on C# program specifically for designing base isolators. A G+4 story RC framed building has been considered for studying the comparative response of fixed base and base isolated buildings.