Earthquake vibrations are natural phenomena that can cause tremors on the ground surface and lead to serious loss of life and property. Especially large-scale earthquakes have the potential to significantly damage infrastructure systems and the durability of structures. Several strategies are available to reduce these damages and increase the resistance of structures to earthquakes. One of these strategies is the implementation of seismic isolators. Seismic isolation minimizes earthquake damage to structures. The main purpose of the study is to examine the effectiveness of the seismic isolator being installed at various story levels of 3D 20-story steel building model. The building had two sets of 20 evaluation models, each with a different isolator story. The first set had identical evaluation models, except for the isolation story which is incremented in each model. The second set is similar to the first set except that the lower stories are strengthened by shear walls. The goal was to determine the best dimensions for the isolator to minimize the inter-story drift values. For this purpose, a set of 12 earthquake records are selected. These records are scaled according to the determined design spectrum. The optimization is performed for one of these earthquake records. Nonlinear dynamic analyses are carried out to evaluate the building model responses for all 12 earthquake records. Response values such as story shear forces and story drift ratios were analyzed and interpreted. This analysis will contribute to a better understanding of the impact of isolators with optimization methods on structural performance