DAMAGE ASSESSMENT OF RC FRAMES SUBJECTED TO BLAST AND POST-BLAST FIRE SCENARIOS

Abstract

In our increasingly urbanized world, the safety and resilience of structural elements stand as paramount concerns. This era confronts structural engineers with the formidable challenge of designing buildings and infrastructure capable of withstanding the destructive forces of explosive events, be they accidental or deliberate acts of terrorism. As cities expand and threats diversify, comprehending the intricate interplay between structural components, explosive forces, and subsequent fire effects is essential for ensuring the robustness of our built environment. Reinforced concrete (RC) elements constitute the backbone of modern infrastructure, making it imperative to grasp their behavior under blast and post-blast fire scenarios to develop effective mitigation strategies and bolster critical infrastructure resilience. Accordingly, this comprehensive study delves into the critical aspects of structural response to blast loading and subsequent fire performance of various structural elements, including RC beams, RC columns, RC frames, and masonry infilled RC frames, and provides valuable insights for enhanced structural design and safety against extreme loading events. The study starts with the critical problem of direct shear failure in structural members exposed to blast events and introduces a novel 3-D finite element (FE) based cohesive interface modeling approach to address this issue in RC members. The research demonstrates that the proposed cohesive interface model effectively captures direct shear failure in fixed-end RC beams, particularly in near-field and close-in blast scenarios, eliminating the need for externally adopted damage criteria used in conventional FE-based monolithic models. A series of numerical simulations show that while both modeling strategies perform similarly in far-field blasts where shear effects are minimal, the cohesive interface model outperforms the monolithic model in near-field and close-in blasts by accurately predicting shear-induced damage and structural response. Further, understanding blast-induced structural damage is essential for designing resilient structures and safeguarding lives. Pressure-Impulse (P-I) diagrams serve as vital tools in the protective design of structures against blast loads, providing insights into failure modes and damage levels. This thesis addresses concerns regarding the reliability of P-I diagrams generated using existing methods, particularly in impulsive and dynamic loading regimes. Consequently, the study employs a 3-D FE-based cohesive interface model with comprehensive damage criteria to generate accurate P-I diagrams for fixed-end RC beams subjected to blast loads. The study highlights the inadequacies of FE monolithic models in generating accurate P-I diagrams, specifically in the dynamic loading regime, where the potential effects of support slip on bending deformation are significant. The results exhibited the effectiveness of FE-based cohesive interface models in generating accurate P-I diagrams over the monolithic models. Therefore, this research has significant implications for enhancing the prediction of structural failure under blast loads and ensuring the safety of protected facilities.