Seismic disasters have historically caused extensive loss of life and severe damage to the built environment, motivating continuous advancements in earthquake engineering and structural design practices. Modern seismic design philosophies emphasize the need to ensure structural safety and resilience under varying levels of seismic loading by integrating both strength-based and deformation-based performance criteria. Contemporary seismic codes, such as the Chinese Code for Seismic Design of Buildings, adopt a multi-level performance framework in which structural strength is verified under frequent and moderate earthquakes, while deformation capacity is evaluated under rare but severe seismic events. Within this framework, the inter-story drift angle serves as a critical parameter for assessing structural performance and estimating potential damage levels during seismic excitation. This study examines the role of inter-story drift limits and elastic response assumptions in evaluating structural safety during seismic events. Most earthquakes experienced by structures are characterized by relatively low intensity or short duration, resulting in responses that largely remain within the elastic range of structural behavior. Under such circumstances, design methods based primarily on elastic analysis are generally sufficient for predicting structural performance and ensuring compliance with code requirements. The approach allows engineers to estimate seismic demand efficiently while maintaining a reasonable margin of safety for typical seismic occurrences. However, the reliability of elastic-based assessments becomes more complex when considering the variability of seismic ground motion and the influence of local site conditions. Differences in soil properties, site classifications, and seismic wave propagation characteristics can significantly affect the time–frequency response of structures. These variations highlight the importance of understanding how response spectra and structural performance indicators behave across different site environments. By exploring the normalized time–frequency response characteristics associated with diverse site types, this research aims to provide insights into the applicability and limitations of conventional elastic-based evaluation methods in seismic design. The findings contribute to improving the interpretation of seismic response parameters used in structural safety verification and offer guidance for enhancing performance-based seismic design approaches. Ultimately, the study supports the ongoing development of more reliable and site-sensitive seismic assessment methods that can better safeguard structures and communities against earthquake hazards.