Strategies to Enhance Column Robustness and Reduce CO2 Emissions in Progressive Collapse Scenarios: A Risk-Based Optimization Approach

Resumo

A significant challenge in structural engineering is the rational design of systems exposed to exceptional events, often referred to as low-probability, high-consequence actions, such as fires, earthquakes, explosions, and impacts. Climate change exacerbates these risks by increasing the frequency and severity of hazards, potentially exposing structural vulnerabilities. Structural robustness refers to the capacity of a structure to withstand such actions, preventing initial and localized damage from escalating into disproportionately severe consequences, such as progressive collapse. Traditional reinforcement techniques, while mitigating risks, are often costly and may be inefficient under uncertain triggering events or simultaneous failure of multiple elements. Moreover, structural reinforcements typically involve unsustainable material consumption, significantly contributing to greenhouse gas emissions, highlighting the urgent need for sustainable alternatives. Studies reveal a notable lack of multifaceted protection techniques capable of addressing different levels and stages of failure in the progressive collapse context. The main objective of this work is to perform a risk-based optimization of alternative protection techniques to mitigate progressive collapse in reinforced concrete systems, focusing on solutions that enhance structural safety through robustness, while prioritizing cost-efficiency and environmental sustainability. The proposed methodology, grounded in structural reliability, accounts for random and epistemic uncertainties in design variables and hazard probabilities, and aims to minimize global collapse probability and the associated risks in terms of costs and CO₂ emissions. The techniques explored include ultra-high-performance fiber-reinforced concretes (UHPFRC), traditional reinforcement approaches (Alternative Load Path method), and the combination of these to achieve optimized solutions. The study focuses on column reinforcement in flat slab parking garages exposed to fire and vehicular collisions, as these structures are particularly vulnerable to column loss due to the punching shear phenomenon and increased fire risk from flammable materials. The results include innovative and robust solutions capable of transforming engineering practices, advancing structural safety, sustainability, and cost-efficiency in the construction sector.