APPENDIX B (Continued)
Using Table D-8 in Appendix D, the required standoff distance for a minimal level of
damage to the building from 1,000 pounds (454 kg) of explosives is 400 feet (122 m). Using
Table D-5 in Appendix D, standoff distance for some injury from debris, but low probability of
death, is 300 feet (91 m). The controlling distance is 400 feet (122 m). Because there is only
about 320 feet (97 m) available for standoff at the location closest to the perimeter (at Building
700), a decision must be made to either close perimeter road "B" to vehicle traffic or accept
"minor" (280 feet or 85 m) damage to the structure. In this case, because the death and injury
goal will be met, acceptance of minor, rather than minimal, damage to the structure could be an
acceptable alternative. Standard glazing systems, on the other hand, will fail under these loading
conditions and should be treated with fragment-retention film or replaced with blast-resistant
glazing systems to reduce potential injury to personnel.
Based on the performance characteristics of the Delta TT207, the penetration distance
of the design threat vehicle, after impact, is 27 feet (8 m). Adding this distance to the distance
required for mitigating the explosive effects, the total standoff distance between the barrier and
the building should be at least 427 feet (130 m). Because this standoff distance is not available
for Building 827 under current site conditions, the next step would be facility hardening or the
acceptance of minor damage to the structure.
Passive barriers along the fence line should be designed to allow little or no
penetration, because available standoff distance is already at the marginal level to protect
personnel against death and injury. Selection of the concrete-filled bollard system (Figure 25)
will provide adequate penetration resistance, because the approach is parallel to the barrier (77%
of the impact load from Table 1 in Section 6).