In many studies on the effect of pounding on isolated structures, the failure to consider all potential pounding scenarios, including floor-to-floor (FF), floor-to-column (FC), and pounding with a moat wall, can introduce uncertainty into the obtained results. Therefore, this study investigates the critical pounding scenarios in isolated structures subjected to seismic excitations. Three primary types of pounding are examined: FF, FC, and MW, under both two-sided and one-sided limitations. Additionally, the study investigates the effects of varying gap sizes and structural heights on the response of structures subjected to each pounding type. In the FF and FC scenarios, six-story and nine-story base-isolated buildings are analyzed in relation to adjacent six-story fixed-base structures. The endurance time method is employed to obtain the seismic responses of the structures. The results indicate that FC pounding consistently induced the highest shear forces in the columns and represented the most critical failure mode. The base-isolated structures that are significantly taller than adjacent fixed-base structures (e.g. 9.6 m) are more susceptible to damage compared to those with similar heights to their neighbors. Furthermore, increasing the gap size can lead to a 100 % rise in inter-story drift under two-sided FF pounding and a 126 % increase in column shear force under two-sided FC pounding.

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.