Structural Reliability of Reinforced Concrete Frames Under Column Removal Scenarios

Structural robustness has been a topic of particular interest, especially after two significant events: the partial collapse of the Ronan Point building in London and the attack on the World Trade Center in New York. These incidents led to an evaluation of the capacity of structures to withstand partial failures that could lead to progressive collapse. International standards, such as the Eurocode and ISO, have developed strategies to enhance structural resistance and reduce the risk of progressive collapse. To evaluate the robustness of a building in a quantitative way, methods such as the "stiffness-based measure" and "energy-based measure" have emerged. These approaches assign a robustness value to the structure, with the goal of determining structural reliability, where probabilistic methods are commonly applied. A practical approach to evaluate structural robustness is the Pushdown Analysis. A practical exercise consists in removing a first-story column from a building and applying an imposed displacement at the location where the column was removed, allowing for a step-by-step observation of the structural response to local damage The Pushdown Analysis is performed using finite element software ATENA 2D v5, evaluating a five-story building with four spans and a regular configuration in plan and elevation. Three different structures are analyzed to evaluate the resistance to progressive collapse by evaluating the structural reliability involving the removal of the second-to-last supporting column. The first structure is designed according to standard codes, while the second and third structures incorporate robustness enhancements regarding the arrangement of the longitudinal reinforcement of the beams.