Comparative Evaluation of Tie Force Requirements for Progressive Collapse Resistance in a Six-Story Reinforced Concrete Building Under Different National Code-Based Input Sets

Progressive collapse has become a critical concern in resilient structural design due to accidental impacts, abnormal loading scenarios, and sudden localized damage events that may lead to the sudden loss of structural elements under extreme or unforeseen actions. In this context, UFC 4-023-03 provides design approaches for improving collapse resistance, including the Alternate Path Method, Enhanced Local Resistance Method, and Tie Forces Method. This study focuses on the Tie Forces Method, which is based on mechanical interconnection but remains relatively underexamined in the literature. A six-story reinforced concrete office building was evaluated to determine the required tie reinforcement area for progressive collapse resistance according to UFC 4-023-03. Ten national building codes were considered, with office live loads ranging from approximately 2.0 to 4.8 kN/m2. In this study, the selected national codes are not compared in terms of their complete progressive collapse provisions. Instead, UFC 4-023-03 is adopted as the main Tie Forces Method calculation framework, while national-code-based live load values and reinforcement properties are used as input parameters. Peripheral, longitudinal, transverse, and vertical ties were comparatively assessed. The largest percentage reduction was observed for the peripheral transverse tie reinforcement at the first floor, where the Eurocode-based input set produced a required tie reinforcement area approximately 21.7% lower than that obtained from the Russian input set. In contrast, Canadian provisions govern the highest demand at the ground floor, while South Korean provisions produce the highest demand at upper floors. Overall, the findings highlight the influence of national live load provisions and reinforcement properties on tie force requirements.