Over the past few decades, civil engineers and researchers have conducted extensive research to advance the understanding of earthquake phenomenon, its characteristics, and the factors influencing structural behavior. The primary goal has been to reduce damage and prevent the collapse of structures against earthquakes. The frequency content of the ground motion is one of the most important factors affecting the dynamic response of structures, playing a vital role in the magnitude of deformations, internal forces, and structural vulnerability. With advancements in technology and increased computational power, the use of more accurate methods in structural analysis has become available. Among these, the Incremental Dynamic Analysis (IDA) method has garnered attention as a novel and credible approach due to its high accuracy and close representation of real structural behavior. This method holds a special place, particularly in assessing the seismic performance of structures and investigating their collapse capacity. On the other hand, steel moment-resisting frames are one of the most common lateral load-resisting systems due to their high strength, ductility, and energy absorption capacity. Therefore, a precise investigation of the behavior of these systems against the earthquake frequency content is essential.
In this study, the influence of earthquake frequency content on the dynamic response of intermediate steel moment-resisting frames was investigated using Incremental Dynamic Analysis in ETABS software. Three representative ground motion records—Tottori, Northridge, and Loma Prieta—were selected to represent high-frequency (FCI > 1.2), medium-frequency (0.8 < FCI < 1.2), and low-frequency (FCI < 0.8) earthquakes, respectively. The structural models analyzed consisted of intermediate steel moment frames (IMFs) with 3, 6, and 9 stories, modeled using nonlinear fiber hinge elements. All models assumed a story height of 3.4 m, with each structure comprising four bay