*3.1. Blast Scenario*

Selecting an appropriate scenario from among the various possible blast events and setting the size of the blast load are essential to the performance evaluation and risk analysis. Blasts that occur on bridges are unpredictable and—on both domestic and overseas bridges—have been caused by explosions from terrorist attacks, vehicle accidents, and other events (e.g., wars). When conducting blast analysis for bridges, most previous researchers have used random blast loads, rather than setting separate blast or vehicle explosion scenarios [14–17,22]. This study defined blast accident scenarios in terms of vehicle-based terrorist attacks, considering the current likelihood of war-related blast accidents to be low. A virtual scenario describing a terrorist attack conducted through explosive-laden vehicles was assumed. Thus, the quantity of explosive (TNT) and height of the explosion above the road were set according to the maximum load and ground clearance of general-purpose vehicles driven in South Korea. A TNT load of 1000–1500 kg was considered, which is classified as a very large load considering the explosive definitions introduced in [29] or the quantities of explosive used in the American Society of Mechanical Engineers-American Concrete Institute explosion tests [30]. Table 4 presents the blast scenario specifications employed in this study.


**Table 4.** Blast scenarios.
