| Terrorist activities have become a much too familiar part of today's society. These events can cause destruction to buildings and bridges, loss of lives, and economic downfall. With these events becoming more common, it is imperative to establish a reliable method to design, evaluate, and retrofit structures for the possibility of such events. While a great deal of research has been conducted in the area of blast resistance related to buildings and retrofits, little has been done to assess bridge performance under blast loading. This thesis focuses on the analytical modeling of blast effects on bridge structures.; The scope of work included gathering background information related to loads caused by blasts and analytical modeling options, as well as a literature review of related research findings. AUTODYN, a commercially available non-linear dynamic program, was selected to conduct this modeling. A study to determine the most appropriate constitutive models considering the dynamic material properties was subsequently conducted. This resulted in the selection of four constitutive models for the four materials incorporated in the modeling---air, TNT, concrete, and steel. A mesh sensitivity analysis was also performed to determine the optimum element size to be used, considering the conflicting interests of increased accuracy and decreased processing speed and memory availability with smaller elements. For this analysis, AUTODYN results were compared against results generated using the empirically based program called ConWep, as well as hand calculations, which also served as a general validation of the accuracy of the program. The results of the constitutive model studies and mesh sensitivity analyses were incorporated in developing a model of a cross-section of a two-lane bridge, where the performance of the cross-section when subjected to a below deck blast was investigated.; Detailed information on the stresses within the deck was obtained. This model indicated that the highest stresses generated in the deck were located approximately half-way between the transverse centerline of the cross-section and the adjacent girder. This result demonstrated the significance of reflected pressure as the increased stress was generated due to the reflection of blast pressures between the deck and the girder. |
