Akademik Veri Yönetim Sistemi
Structures, cilt.80, 2025 (SCI-Expanded, Scopus)
Past devastating earthquakes highlight the importance of seismic-resilient design and proper construction practices for reinforced concrete (RC) buildings. One of the most common structural deficiencies causing collapse of RC buildings is the stiffness irregularity, between adjacent stories, which is termed as the soft-story irregularity. Seismic design codes assess soft-story irregularity using either the relative story stiffness ratio or the inter-story drift ratio (ISDR). This study investigates the reliability of these criteria through a parametric analysis of 5-, 10-, and 15-story RC frame buildings designed as per code requirements. Soft-story irregularity was introduced by varying the ground story height. Lateral target displacements of the buildings under Design Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE) levels were estimated using nonlinear pushover analyses considering the first modal shape. RC buildings with low relative story stiffness ratios may not be classified as having soft-story irregularity by the codes that rely on relative ISDR. While increasing the ground story height leads to higher story drift, the greater height in the denominator reduces the sensitivity of ISDR to detect soft-story irregularity. Using the relative story stiffness parameter offers a more consistent and meaningful approach for identifying soft-story behavior. Based on the results, it was observed that the TBEC (2018) criterion fails to detect soft-story irregularities in buildings with significantly reduced ground story stiffness, whereas ASCE 7–22 provides a more consistent identification in line with observed damage patterns. As the story stiffness ratio (k₁/k₂) decreases, drift demands and seismic damage tend to localize in the ground story, increasing the risk of story mechanism formation.