Base Isolation Towards Seismic Resilient Infrastructures In Rwanda

Rwanda’s population growth and density on a small area is increasing very fast;the increase in urbanization and population growth rate pushed the government to devise modern ways of optimal land use to ensure sustainable growth.High rise buildings construction is being promoted as a response to the high rate of urbanization and land shortage.However,their current building regulations refers only to British Standards,BS EN 1998 Eurocode 8,with a PGA of 1.6 m/s~2 and a return of 475 years for designing Earthquake resistant buildings without any other isolation technique being implemented while several researches revealed that many structures designed according to seismic codes have not exhibited adequate structural performance during some strong earthquakes.To ensure that these newly developed structures in Rwanda are seismically safe and more resilient,base isolation using friction pendulum bearing has been suggested as sustainable solution in this study.This thesis’s aim is to analyze the seismic response of building structure isolated with single friction pendulum bearing while subjected to earthquake ground motion taking Rwanda as the case study.A single degree of freedom RC frame structure system model was developed and its seismic response were analyzed while both fixed-base and isolated by a single friction pendulum bearing and results revealed that FPB is effective.The impact of vertical ground acceleration component has been highly emphasized in this study and indicated that it doesn’t have to be neglected in estimating seismic horizontal response of FPB-isolated system as it plays a great influence on structure’s seismic response.Even though FPB is not a new base isolation technique,the effect of each of its design parameters on the isolation system response was not well discussed yet.In this study the effect of design parameters including radius of curvature,friction coefficient,supported structure’s mass,and the design displacement have been discussed.A one dimensional mathematical model was developed to further understand how these parameters affect the response;several essential conclusions can be drawn including the fact that the effective Stiffness is dependent not only the radius of curvature but also the friction coefficient.The understanding of the design parameters will then be helpful to optimally design a friction pendulum bearing isolation system for a particular application that will minimize the shearing displacement of the structure during an earthquake.The results revealed that a single friction pendulum designed with radius of curvature of 1.5m and friction coefficient of 0.06 with a design displacement considered to be 0.2m in the current study can be effective and able to contribute in the structure protection.