Performance of FRP-concrete bridges under blast loading

Catastrophic failure from intentional terrorist attacks on surface transportation infrastructure could he detrimental to the society. In order to minimize the vulnerabilities and to ensure a safe transportation system, the issue of security for transportation structures, primarily bridges, which are subjected to man-made hazards is investigated in this study. A procedure for identifying and prioritizing "critical bridges" using a screening and prioritization processes is established. For each of the "critical" bridges, a systematic risk-based assessment approach is proposed that takes into account the combination of threat occurrence likelihood, its consequences, and the socioeconomic importance of the bridge. A series of effective security countermeasures are compiled in the four categories of deterrence, detection, defense and mitigation to help reduce the vulnerability of critical bridges. The concepts of simplified equivalent I-shape cross section and virtual materials are proposed for integration into a nonlinear finite element model, which helps assess the performance of reinforced concrete structures with and without composite retrofit or hardening measures under blast loading. A series of parametric studies are conducted for single column and two-column pier frame systems as well as for an entire bridge. The parameters considered include column height, column type, concrete strength, longitudinal steel reinforcement ratio, thickness, fiber angle and tensile strength of the fiber reinforced polymer (FRP) tube, shape of the cross section, damping ratio and different bomb sizes. The study shows the benefits of hardening with composites against blast loading. The effect of steel reinforcement on blast resistance of the structure is more significant than the effect of concrete compressive strength. Moreover, multiple blasts do not necessarily lead to a more severe destruction than a single detonation at a strategically vulnerable location on the bridges.

Fear and U.S. foreign policy during the Truman administration, 1945-1952

The purpose of this study was to investigate how the Truman administration used fear to generate popular support for its Cold War foreign policies. Three issues were examined through the use of published government documents, personal memoirs, and weekly periodicals to assess the responses of the American public: the enactment of universal military training (UMT), the Soviet detonation of an atomic device, and the Truman administration's decision to build the hydrogen bomb. This study shows that the changing attitudes in the Truman administration toward the Soviet Union occurred in a climate of fear. Through press releases and by exerting influence on the media, the administration attempted to control the information the public received. Through the use of propaganda, the Truman administration pursued the implementation of UMT, generated fear of the Soviet Union after its detonation of the atomic bomb, and gained relative public support for the decision to build the hydrogen bomb.