The purpose of this research is to assess the performance of an American Association of State Highway and Transportation Officials (AASHTO) girder bridge under blast loading. The AASHTO has specified probability based design methodology and load factors for designing bridge piers against ship impact and vehicular collision. Currently, no specific AASHTO design guideline exists for bridges against blast loading. Structural engineering methods to protect infrastructure systems from terrorist attacks are required.
Bridges are unique in terms of materials used, length, width, skewness, span, loading, traffic conditions, and overall geometry. This research investigated the most common types of concrete bridges on the interstate highways. A 2-span 2-lane bridge with Type III AASHTO girders was used for modeling. Girder spacing was chosen based on the span length and loading conditions. AASHTO Load and Resistance Factor Design (LRFD) methods were used for bridge design. Performance of AASHTO girders, piers and columns under typical blast loading were analyzed and documented for future use in blast resistant design of concrete bridges.
The model bridge failed under typical blast loads applied over and underneath the bridge. The research findings concluded that the AASHTO girders, pier cap and columns could not resist typical blast loads. The amount of blast loads, which the individual members can resist before failure, was determined. The model bridge columns were capable of resisting typical blast loads if the explosion occurs at a minimum standoff distance. From these research findings, necessary measures to protect existing bridges from explosion impact are specified and recommended for bridge modification and design guidelines.
