This study assesses the effectiveness of seismic base isolation using triple friction pendulum isolators (TFPIs) as a retrofitting strategy for a five-story steel building. This building is characterized by vulnerable Satchel connections, which suffered extensive brittle failures during the 1990 Manjil and 2003 Bam earthquakes in Iran. Four different experimentally calibrated Satchel connection configurations (S1 to S4) were modeled within a typical five-story building. These configurations varied in parameters such as rotational stiffness (780t.m/rad to 1380t.m/rad), angle lengths (15 cm to 20 cm), and beam sections (IPE180 and IPE220). For each of the four building models, all connections were uniformly assigned one of the four specimen types. The structural and non-structural performance of these models was evaluated using nonlinear endurance time (ET) analysis. The assessment covered seismic hazard levels corresponding to 475-year, 2475-year, and return periods beyond 2475 years. The results showed that implementing a base isolation system avoids the need for extensive strengthening of the existing connections. Moreover, by adding the isolators to the current connections, the structure’s performance can significantly surpass that of a brand-new, code-compliant design.