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Explores code-ready language containing general design guidance and a simplified design procedure for blast-resistant reinforced concrete bridge columns. The report also examines the results of experimental blast tests and analytical research on reinforced concrete bridge columns designed to investigate the effectiveness of a variety of different design techniques.
The increase of worldwide terrorist attacks on public transportation has heightened our concerns of protecting the nation’s transportation infrastructure. Highway bridges are an attractive target for terrorist attacks due to ease of accessibility and their overall importance to society. The primary objective of this research is to investigate multi-hazard seismic-blast correlations of blast-induced bridge components through numerical simulations of a high-precision finite element model of a typical highway bridge in New York. Seismic-detailing for blast loading on bridges has been investigated to study the correlations between seismic design for blast load effects. High-precision 3D Finite Element models of bridges detailed for blast-resistant applications have been developed by designing the bridges for various seismic zones. In total, 9 cases of simulations for blast-induced bridges have been simulated. From the simulations, four failure mechanisms were observed and have been identified. Results from the simulation suggest that bridges detailed with higher seismic capacities were able to resist more blasted-induced failure mechanisms. The amount and location of transverse reinforcement in bridge columns played a significant role for better blast resistance. Although, there are several failure mechanisms that arise from blast loadings that do not take place in seismic conditions.
A proposed paradigm in engineering of bridges prone to the effects of multiple hazards calls for designing and detailing new bridges, as well as retrofitting existing bridges, so that an integrated structural concept provides protection against all credible hazards. This multi-hazard approach is believed to lead to structural systems that are optimal and offer a more uniform level of safety against various credible relevant hazard scenarios. Toward this objective, research was conducted to develop and experimentally validate two proposed structural concepts capable of achieving the objective of multiple hazard protection for highway bridges, namely Concrete Filled Double Skin Tube (CFDST) and Modified Steel Jacketed Columns (MSJC). CFDST is proposed as seismic and blast resistant column for new bridge multi-column bent. MSJC, on the other hand, is a "retrofit-of-the-retrofit" concept which adds blast protection to the capability of Steel Jacketed Column (SJC) already known to provide seismic resistance. Performance of CFDST is investigated both under cyclic pushover and blast tests whereas MSJC is tested under blast loading only using ℗ơ scale column prototypes. The energy dissipation of CFDST under cyclic loading was found to be excellent. Under credible blast scenario, CFDST deform in bending without significant loss in capacity to carry load. For near-contact explosion, another energy dissipation mechanism is engaged in the form of cross-section deformation. In both credible and near contact blast explosion, MSCJ is found to be able to develop large flexural deformations which are not achievable with non-modified SJC that are usually prone to direct shear failure. Equations are also presented to help designer predict the behavior of CFDST under blast and earthquake loads.^Comparison to the experimental data generated in this research as well to data available in the literature shows that those analytical results are accurate, and in some instances conservative.
Chapter 1. Introduction -- Chapter 2. Reliability models for combinations of extreme events -- Chapter 3. Calibration of load factors for combinations of extreme events -- Chapter 4. Conclusions and future research -- References -- Glossary of notations -- Appendixes.
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.
It is found that prototype bridge CFST columns can be designed to provide both satisfactory seismic performance and adequate blast resistance. It is also shown that, in two series of tests at 1/4 scale, the CFST columns exhibited ductile behavior while the RC and steel jacketed columns failed at their base in shear. Based on the experimental and analytical observations, simplified analytical methods for the design of bridge columns under explosive loads were proposed.
Terrorist attacks and other destructive incidents caused by explosives have, in recent years, prompted considerable research and development into the protection of structures against blast loads. For this objective to be achieved, experiments have been performed and theoretical studies carried out to improve our assessments of the intensity as well as the space-time distribution of the resulting blast pressure on the one hand and the consequences of an explosion to the exposed environment on the other.This book aims to enhance awareness on and understanding of these topical issues through a collection of relevant, Transactions of the Wessex Institute of Technology articles written by experts in the field. The book starts with an overview of key physics-based algorithms for blast and fragment environment characterisation, structural response analyses and structural assessments with reference to a terrorist attack in an urban environment and the management of its inherent uncertainties.A subsequent group of articles is concerned with the accurate definition of blast pressure, which is an essential prerequisite to the reliable assessment of the consequences of an explosion. Other papers are concerned with alternative methods for the determination of blast pressure, based on experimental measurements or neural networks. A final group of articles reports investigations on predicting the response of specific structural entities and their contents.The book concludes with studies on the effectiveness of steel-reinforced polymer in improving the performance of reinforced concrete columns and the failure mechanisms of seamless steel pipes used in nuclear industry.