Seismic Vulnerability Assessment of Residential RC Buildings in Yemen Using Incremental Dynamic Analysis (IDA)

Traditional buildings constructed in Yemen during the 20th century often lacked adequate seismic protection. Today, most reinforced concrete (RC) residential buildings in the country are designed with beam–column systems that primarily carry gravity loads without considering lateral seismic forces. As a result, these structures are potentially vulnerable to earthquakes and require further investigation. This study aims to develop analytical seismic fragility curves for residential RC buildings in Yemen with varied heights. Three building heights were considered, namely three, five, and seven stories. While in most studies, the infill walls are regarded as non-structural elements, and their contributions to resisting earthquake actions are ignored, in this study, the contribution of the infill wall was taken into account by utilizing a compression strut modeling of the infill wall. In addition, an investigation was conducted to study the effect of soft stories on the seismic vulnerability of residential RC buildings. Finite element models were developed, and 900 Incremental Dynamic Analyses (IDAs) were conducted. Three damage limit states were defined: Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP). Based on these results, cumulative distribution functions (CDFs) were calculated to derive the seismic fragility curves. The findings indicate that taller buildings are more likely to reach or exceed the defined damage states, making them more vulnerable to earthquakes. Infilled frame structures demonstrate better seismic performance due to the contribution of infill walls to lateral resistance. In contrast, buildings with soft stories are more vulnerable due to abrupt changes in stiffness, resulting in greater deformation concentration in the soft story. The developed fragility curves provide a quantitative basis for assessing seismic damage in Yemeni RC residential buildings and offer a foundation for future seismic risk evaluations.