Numerical Prediction of the Dynamic Response of Prestressed Concrete Box Girder Bridges Under Blast Loads

Significant research has been performed on the response and retrofit of buildings under blast loads. Limited research exists on the response prediction and protection of bridges under near-field blast loads. This research focuses on the evaluation and assessment of box girder bridges under blast loads. The objective of this research is to develop a numerical model to predict the damage level in a concrete deck under blast loading and the corresponding dynamic response of the damaged bridge system. The damage level will be function of spalling/cratering the bridge will suffer under the near field detonations. The numerical analysis conducted using the explicit dynamic software LS-DYNA®, which has the abilities to model the blast load propagation towards bridge structures and to its response to these types of impulsive loads. The bridge has a simply supported span of 100 ft (30.48 m) and was designed according to the LRFD manual under HL-93 truck load. Different charge weights were located at a height of 30 inches (0.762 m) between the main vertical webs at the mid-span. The study shows that LS-DYNA predicted the damage severity under blast loads, especially since the testing under these loads might not be feasible. The studied Key parameters were the weight of the charge, and concrete deck properties. The results of this study make the finite element modeling an attractive alternative for blast testing when it is not feasible like the case of bridges. Comparisons of the numerical results are still necessary for code verification before this study can be expanded for additional parametric studies and design recommendations