Earthquake is one of the major disaster in the world which can be predicted but cannot be forecasted. Some recent ground shaking indicates that Bangladesh is under risk of lot of earthquake source in and around its territory. Seismic isolation is a creative and advanced technology for the protection of a variety of buildings that have the need of earthquake resistance beyond conventional solutions. However, in Bangladesh, this research is still in offspring stage for building structures. Therefore, the main objective of this study is to know the performance of a seismically isolated structure and retrofit a structure with isolation system which will be resistant to a predicted earthquake and will be most cost effective.
Firstly, a 6-story existing RC building located in the high seismic zone of Bangladesh has been taken as the target building for this study. 3D FEM modelling of the building was done with and without seismic isolators by using the software STERA 3D and dynamic nonlinear analysis was done against some earthquake data. The performance effect of both buildings was compared and the suitable property of the isolator was selected. To provide that suitable property, different arrangements with the different number of isolators were selected and the required structural design was made for those arrangement. Finally, cost comparison for different arrangements was made to find the lowest cost solution for seismic isolation.
It was revealed that, although using the isolator increases overall displacement of the structure to a larger value, it reduces the relative story drift to a greater extent. Though this research focuses on a specific example of retrofitting, it serves a purpose of designing isolators which can be used in the new multistoried residential buildings prudently to reduce the member size and reinforcement to lower the overall cost of the building.
Keywords: Seismic isolation, Dynamic analysis, Retrofitting, Cost