<p>Many studies have employed the Alternate Load Path method to investigate the progressive collapse of building structures, yet they often neglect the influence of blast loads, which leads to inaccurate predictions of buildings structures progressive collapse mechanism. In this paper, a comparative experimental analysis was conducted on six reinforced concrete substructures subjected to explosion loads and one ALP-designed benchmark structure to examine their progressive collapse mechanism. The results indicated that the column-end force–time curves of the rubber test device exhibited higher peak forces with shorter durations, whereas those of the airbag test device showed lower peak forces but longer durations. The initial blast-induced damage in the substructures significantly reduced their rotational resistance capacity and accelerated the premature fracture of longitudinal reinforcements at beam ends. Consequently, the blast-damaged substructures exhibited a worse ductility performance compared with the benchmark structure. Moreover, during static pushdown loading, the vertical deformation profile of the benchmark substructure evolved from a double-curved shape to a straight line, while the blast-damaged substructures deformed primarily in a straight-line mode from the outset due to initial blast damage. These findings might provide valuable experimental evidence and design insights for enhancing the blast resistance design and progressive collapse analysis of building structures.</p>