The topic of this thesis is base isolation. The purpose of this thesis is to offer a relative understanding of the seismic performance enhancements that a typical 12-story steel office building can achieve through the implementation of base isolation technology. To reach this understanding, the structures of a fixed-base office building and a base-isolated office building of similar size and layout are designed, their seismic performance is compared, and a cost-benefit analysis is completed. The base isolation system that is utilized is composed of Triple Friction Pendulum (TFP) bearings. The work of this thesis is divided into four phases. First, in the building selection phase, the structural systems (SMF and SCBF), layout, location (San Diego, CA), and design parameters of the buildings are selected. Then, in the design phase, each structure is designed using modal response spectrum analysis in ETABS. In the analysis phase, nonlinear time history analyses at DBE and MCE levels are conducted in PERFORM-3D to obtain the related floor accelerations and interstory drifts. Finally, in the performance assessment phase, probable damage costs are computed using fragility curves and FEMA P-58 methodology in PACT. Damage costs are computed for each building and seismic demand level and the results are compared.