Application of the Base Isolation Systems to a Reinforced Concrete Building and Cost Analysis

The structures designed using classical methods withstand the seismic effects by their own, thus, the stiffness and the elasticity of the structures are generally improved to react the large static and dynamic loads. Improved levels of stiffness and elasticity results in additional effects to the structural system and requires materials of high quality and larger cross-sections. The methods that predict the potential loads to the structure to generate the withstanding forces or the inclusion of the isolators between the superstructures and their foundations are regarded as new design concepts. By means of these methods, also called the structural control systems, human life, strategic structures and valuable equipments are more safely secured compared to the classical methods.In this study, a passive control system, base isolation, was applied to a four-storey reinforced concrete building using lead-plug rubber isolators. The isolators were designed under the rules of Uniform Building Code-1997, and for the same structure, base shear forces for two different design configurations were computed. In the first configuration, a straightforward fixed base structure was used, whereas, in the second configuration, a seismic isolated structure was utilized. The amount of decrease in terms of the seismic forces that affect the superstructure was observed through the results of the two configurations. For the sample seismic isolated structure, the effects of the structure periodical change which depends on the isolator height, horizontal shifts of the isolators designed, and the variation of the rubber layer to the maximum vertical load capacity of the isolators were investigated. Besides, prices of the lead-plug rubber isolators were obtained from two different companies to analyze the potential amount of change of the costs during the production of the seismic isolated structure compared to the prices of a classical fixed base structure.