Development of simplified dynamic response models for blast-loaded bridge components

Sammarco, Eric Louis
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International terrorist organizations have been active across the globe for decades, but attacks against public surface transportation infrastructure constitute a recent trend. Statistical data from past attacks, along with numerous threats received by United States (U.S.) Government authorities, support this claim and render U.S. transportation infrastructure security a national concern. Public highway bridges can be particularly vulnerable to a malevolent attack due predominately to their public accessibility and exposed nature. Furthermore, the sudden failure of a highway bridge located on a major transportation corridor has the potential to cause significant economic loss, human casualties, and societal distress. Motivated by the recent trend of increasing worldwide attacks and identified vulnerabilities associated with public highway bridges, considerable research in the area of bridge security has been carried out over the past decade. While much research is still needed, it is important to begin transitioning the existing knowledge and technology to the appropriate users within the bridge analysis and design community. Accordingly, the main objective of the research described in this dissertation is to facilitate this transition and advance the state of-the-practice in bridge-specific protective analysis and design by developing accurate yet fast-running dynamic response models for reinforced concrete (RC) bridge columns and tower panels subjected to blast loads. Given a threat scenario and bridge component of interest, the RC component response models characterize demand on a selected component and provide an estimate of peak dynamic response and incurred damage. Such fast-running, engineering-level models provide practicing bridge engineers with the ability to readily assess the performance of blast-loaded bridge components without having to rely on time-consuming, costly, and complex resources such as physical testing or high-fidelity finite element simulations. The proposed dynamic response models are also capable of facilitating anti-terrorist/force protection (ATFP) retrofits and rapid in-situ vulnerability assessments of existing bridge components, as well as safe designs of new bridge components. As part of a larger research effort that was chiefly managed by the author of this dissertation, the RC component response models were integrated with similar models for steel bridge towers and high-strength steel cable components to form a comprehensive, component-level vulnerability assessment software for blast-loaded bridges. Therefore, the results of this research synthesize the state-of- the-art in blast-resistant bridge analysis/design and put forth a practical, engineering-level tool to aid in the growing concern of domestic transportation infrastructure security. This contribution to the structural engineering community marks a step towards enhanced resiliency of existing and future U.S. highway bridges.