Evaluation of Progressive Collapse Risk in Reinforced Concrete Structures Considering Soil–Structure Interaction via the Winkler Model

Progressive collapse refers to a cascading sequence of failures initiated by localized damage, potentially resulting in partial or total structural collapse. Typically, it is initiated by the failure of one or more primary structural element, this phenomenon necessitates specialized analysis under abnormal or unforeseen loading conditions. Recent global events have emphasized the need to incorporate progressive collapse considerations into structural codes. Equally important is the role of soil–structure interaction (SSI), which significantly influences superstructure behavior. This study investigates the progressive collapse potential of a reinforced concrete structure considering SSI effects through the Winkler Soil Model with three different subgrade modulus values (stiff, medium, and soft soils). Nonlinear dynamic analyses were performed in SAP2000, following the Alternate Path Method from the UFC 4-023-03 guideline. Three column removal scenarios were analyzed to assess how varying soil stiffness influences collapse mechanisms. Findings reveal that soil stiffness has a substantial impact on the formation and distribution of plastic hinges and structural displacements. Comparisons between fixed-base and soil-supported models highlight the necessity of including SSI in progressive collapse assessments. The study offers practical insights for enhancing structural resilience by emphasizing the critical influence of soil properties on collapse behavior.